I wrote an article on sleep tips for anyone starting university. You can read it in full below 🙂
A friend recently brought my attention to the latest Lush product which had literally been “blowing up her Instagram”. After seeing news articles such as this, I wanted to find out whether the evidence supported the hype. Now, before I start, I want to say that I have absolutely no problem with people paying for what they feel helps them. If you suffer from insomnia and find that this product helps you where other products have not then please keep using it. However, I want to draw attention to the tenuous support for its active ingredients and the fact that most people would benefit just as much from taking a hot bath and introducing a bunch of flowers into their bedroom. At a sell-out price of £13.95 for 215g it strikes me there should be some strong evidence to back up its miraculous effects.
So, what is the evidence for the soporific effects of Lush’s latest goop? Well, the website argues that because the cream contains lavender and oatmeal that this should help individuals drift off to sleep. To quote the Lush website, “You’ll sleep well after dipping into this dreamy lotion, made with a gentle oatmeal infusion, calming lavender flower and comfortingly sweet tonka absolute.” According to the reviews on the website, and social media, this seems to be the case. The main reason for this appears to be the relaxing and anti-anxiety properties of the cream which plenty of customers are swearing by. However, what is the research evidence that this expensive cream does what it says on the tin?
Let’s assess the key ingredient, lavender. I have chosen to focus on lavender as this is the only active ingredient I could find which had any research linked to sleep (apparently tonka beans and oatmeal are great to eat though). Lavender oil has been championed as a natural way to improve sleep in healthy individuals and those suffering from insomnia. There are numerous blogs which support its use and there is even a brief reference to it on NHS resources for insomnia. Nonetheless, neither of these prove that lavender oil has a genuine impact on sleep beyond a placebo effect. It may be that the expectation that lavender will improve sleep or increase relaxation is responsible for its positive effect.
This exact point was shown clearly in a study conducted almost ten years ago by Siobhan Howard & Brian Hughes in the British Journal of Health Psychology. They found that it was the expectation of an effect, and not the lavender aroma itself, which was responsible for the calming effects it produced. They asked participants to smell either a jar of lavender oil or a jar full of a control aroma (tea tree). Following this, their levels of relaxation (measured objectively using galvanic skin response) and self-reported anxiety were assessed. The researchers found no effect of lavender oil on either of these measures. However, when participants were told that the oil would enhance relaxation, as compared to decrease it, they found that objective relaxation levels increased. The opposite was found when participants were told the lavender would decrease their relaxation levels. This effect was not found for the self-report measure of anxiety. This suggests that simply being told lavender oil is relaxing or not is enough to produce a physiological relaxation response.
Admittedly, this is one study. So what does the wider pool of research suggest? Well typically we can go to a systematic review to see a summary of all of the research in an area but there are few reviews assessing lavender and sleep. There are a couple on aromatherapy and complimentary medicine’s effect on sleep but these include a small number of, or no, studies examining lavender oil. So, like any good scientist, I decided to conduct a quick systematic review myself. This was done in a shorter time than you would do a typical review so please tell me if I’ve missed anything critical (*I can provide anyone with the documents and stages of my systematic review so you can work through them if you’re super interested or are keen to prove me wrong). However, I’m guessing most of you just want to hear whether the research supports the use of lavender, right? Does the research support its widespread use? Well the short answer is no, not especially. The longer answer is that the evidence conducted in this area is largely poor and very little has been done in healthy individuals in a non-clinical setting so it is hard to ascertain whether there is a true effect here. What were the main problems with these studies? Well, most of these studies did not adequately control for the problematic issue of placebo effects. A failure to account for this by not including an active control (e.g. a control which is comparable to the treatment) can inflate the effects of any potential intervention. This is dishonest as it creates an biased view of how successful a specific drug or therapy is compared to the effect of expectation that a therapy will work. It’s admittedly not that unusual in drug trials (see everything by Ben Goldacre) but it is important to understand if you want to know whether you haven’t just got an expensive placebo in front of you. Placebo effects can produce meaningful changes to health but it is much cheaper to take a sugar pill than an expensive therapy and it is important to be aware of this in healthcare.
The importance of considering placebo effects was highlighted clearly in one study identified via my search. On first glance, it appeared that smelling lavender oil over 8 weeks had a big impact on perceived sleep quality (a 40% improvement in sleep from the initial baseline). Pretty good, huh? Well, when the researcher analysed the findings from the placebo condition (e.g. smelling distilled water, not a perfect control but better than nothing), they found a 27% improvement in sleep scores from the initial baseline. This means that, accounting for placebo effects, a 13% improvement in sleep, over 8 weeks, was found after smelling lavender oil for an hour before bed. This is admittedly still bigger than 0 but the improvement of 13% is fairly negligible for participants who were already sleeping well in this experiment. One study did conduct their experiment on self-reported poor sleepers but found no effect of lavender oil on any individual sleep diary measurements. When sleep was assessed using an established sleep questionnaire (the Pittsburgh Sleep Quality Index) they did find a significant improvement in sleep quality for participants wearing a patch containing lavender oil compared to a control (an identical patch contained nothing). This suggests that lavender oil delivered as a patch may improve sleep in college students. However, it is hard to say whether expectancy effects played a part here as despite the claim that the participant and experimenter didn’t know which patch they received, the absence of oil in one and presence in another is something I’m not convinced a participant wouldn’t notice. Happy to be argued against.
The only other study conducted on healthy young adults was carried out by Goel and colleagues in 2005. They found that lavender oil (compared to odourless water vapour) produced a small increase in deep sleep for the first half of the night. This is interesting as deep, or slow wave, sleep is important for a number of different cognitive functions including memory. By including this study, that produces the grand total of 3 research papers which assessed the effect of lavender oil in a sample equivalent to the claims made by Lush. The other studies included those in an intensive care unit (ICU) following surgery, elderly individuals suffering from dementia, participants with chronic liver failure, postnatal mothers, those with major depressive disorder, and those in the ICU for an undisclosed reason. I’m not saying we can’t learn anything about the effect of lavender oil on sleep from these samples but they are considerably different in the reasons for their sleeplessness. A busy and stressful ICU ward is a different environment than say a bedroom in your own home. Nonetheless, I’ve included all of the other studies in a table for your perusal below so you can make up your own mind on whether I should talk about these more (these are even less conclusive than the studies I’ve talked about above).
So why might we see a positive effect of lavender infused cream on sleep if there is such weak evidence to support its use? Well, one clear contender which I’ve harped on about is the placebo effect. I’m sure I will receive plenty of flak for this but it has been consistently shown that placebos, even if we know they are placebos, can produce dramatic results on our health. In respect to sleep, simply being told you are sleeping better (even if this is objectively false) can produce an increase in functioning. I don’t doubt or question the effect of a powerful placebo and I have no problem with people using things which help a problem they have considered previously intractable. What I do have a problem with is people paying £13.95, or more, for a product which is no more effective than a warm bath and good sleep hygiene. This is an issue hardly confined to Lush or their products. I am sure there are many spending much more on other products in the hope of finding a solution for their insomnia.
So, what do I recommend instead of paying for expensive goop and smothering it over yourself on a nightly basis? I mean, surely, I should put forward a counter suggestion if I am going to claim ‘Sleepy’ isn’t based on sufficient evidence to support its claims. Well, firstly, if you are suffering from insomnia then go to see your GP in the first instance and consult resources created by clinical and academic experts in insomnia. These should be your first port of call and both will provide scientifically proven advice on how best to manage your sleeplessness. If products such as ‘Sleepy’ work wonders for you and you’re happy to pay for them then ignore me – I promise I won’t be offended. However, try to incorporate your own relaxation methods into your bedtime schedule and see whether these can replace ‘Sleepy’. If they don’t then go back to scented creams safe in the knowledge you’ve proven me wrong. However, if they do then do yourself a favour and save yourself the time and money which Lush’s product requires.
Alternatively, Lush could provide me with enough free cream to run a large randomised controlled trial of this stuff. Just sayin’.
*If you want more information about the systematic review leave a message below and I’ll happily email you the documents.
Goel, N., Kim, H., & Lao, R. P. (2005). An olfactory stimulus modifies nighttime sleep in young men and women. Chronobiology international, 22(5), 889-904.
Howard, S., & Hughes, B. M. (2008). Expectancies, not aroma, explain impact of lavender aromatherapy on psychophysiological indices of relaxation in young healthy women. British journal of health psychology, 13(4), 603-617.
Lillehei, A. S., Halcón, L., Gross, C. R., Savik, K., & Reis, R. (2016). Well-Being and Self-Assessment of Change: Secondary Analysis of an RCT That Demonstrated Benefit of Inhaled Lavender and Sleep Hygiene in College Students with Sleep Problems. Explore: The Journal of Science and Healing, 12(6), 427-435.
Kamalifard, M., Farshbaf Khalili, A., Namadian, M., Ranjbar, Y., & Herizchi, S. (2017). Comparison of the effect of lavender and bitter orange on sleep quality in postmenopausal women: a triple-blind, randomized, controlled clinical trial. Women & Health, (just-accepted).
** (Read this and then read Bad Science if you’re interested in placebo effects and how science can be spun to support absolute rubbish) Goldacre, B. (2012). Bad pharma: how medicine is broken, and how we can fix it. HarperCollins UK.
** (Great page from the NHS which summarises my points on why we need to be concerned about what is placebo and what is not in healthcare) http://www.nhs.uk/Livewell/complementary-alternative-medicine/Pages/placebo-effect.aspx
Anyone with even the slightest fear of creepy crawlies has probably been in the following situation. You settle down for the evening and quick as a flash you see a behemoth of a spider run out. It dashes underneath the sofa before you can react, and, your night ruined, you are left waiting for it to kill you. After a while you’ll convince yourself that it has probably gone to sleep and, seeing as it’s 2am, you should too. However, did it go to sleep? Do insects sleep at all?
One of the many questions which I get when I tell people that I study sleep is some variant of: do insects sleep? What is the smallest creature that sleeps? Do you sleep? Well let’s delve into the world of the mini-beasts to find out the answer to that first one.
Many insects such as bees, moths, cockroaches, and butterflies (to name but a few) will show behaviours that seem indicative of sleep: relative immobility, increased arousal threshold (e.g. harder to wake them up), and drooping antennae. Insects don’t have eyelids so they can’t get “shut-eye” in the usual sense but these other behaviours look a lot like sleep. However, is this really sleeping? Some have argued that the pattern of inactivity shown by some insects can be better referred to as torpor. This is like sleep but torpor involves enhancing the survival of the organism during times of limited resources or when in a harsh environment (e.g. low temperatures during winter). Torpor is often compared to hibernation in mammals and referred to as a ‘mini hibernation’. Unlike sleep, torpor is regulated by external factors rather than an internal clock as in humans and other mammals. However, if what we see is simply torpor in insects then we would not expect them to experience difficulties in functioning after sleep deprivation. So, do insects show signs of poor functioning if they don’t sleep even during normal environmental conditions?
The science suggests that they do.
For example, fruit flies show patterns of inactivity remarkably similar to human sleep – they show recovery sleep, struggle with vigilance and performance after not getting enough rest, and show a steady rhythm of wake and sleep. One well researched example of the effects of sleep loss on bugs can be seen in honey bees. As they mature into foragers for a hive they move from near constant activity to strongly structured patterns of activity and rest as they hunt for food. However, when foragers are not able to sleep they show difficulties in successfully carrying out vital tasks – for example, dancing. For bees, dancing is a vitally important skill (honestly). While away from the hive bees can communicate with one another through a display known as the ‘waggle dance’. This figure of eight movement, interspersed with a slight waggle, is meant to tell other bees about the distance and direction of food sources, pollen, and the hive. Now, how exactly do you deprive a bee of sleep without interfering with its daily schedule? I’m glad you asked. You use something aptly named the ‘Insominator’.
This fantastically named device is a beautiful example of the awful sense of humour scientists possess. The device was developed with the express purpose of ensuring that bees were sleep deprived in an automatic manner while still being part of their hive. Like humans, research should try not to interfere with the daily schedule of participants (no matter how many legs they have) so we can be more confident it was the thing we’re interested in, and manipulated in some way, which is responsible for the effects observed. Despite its funny name, it was actually a pretty cool piece of kit and allowed the bees to go about their social activities (bees are rather social) whilst only disrupting their sleep.
In the study led by Prof. Bennett Klein, they compared the performance of bees’ waggle dance before and following sleep deprivation. Interestingly, when the bees were kept awake they were less able to effectively carry out the waggle dance and alert other bees to resources. More specifically, the bees were less accurate in conveying direction information to other bees and this in turn, it is predicted, would negatively impact foraging behaviour of other bees in the hive. As is seen in other social creatures, and me without a strong coffee or five, sleep deprivation impaired communication skills of these honey bees. Although the mechanisms are more complex in humans it suggests that certain insects do sleep and that this can have a negative impact on social functioning. Although the jury is still out as to whether the rest shown by many insects constitutes sleep, the effects of a lack of this inactivity seem to mimic the effects seen in humans. At this point, I’ll let you make the decision whether we can call this sleep or not. Alternatively, if you have any ideas on how to study whether an insect sleeps, please send your answers in on a postcard addressed to Jack and marked ‘SCIENCE’.
So, if anyone asks you whether insects sleep you can go forth and spread the unclear, slightly contentious, word. Alternatively, you can just remember that bees dance, scientists have a terrible sense of humour, and that the spider still underneath your sofa is asleep. Probably. In fact, it’s probably best just to seal off that room.
Klein, B. A., Klein, A., Wray, M. K., Mueller, U. G., & Seeley, T. D. (2010). Sleep deprivation impairs precision of waggle dance signaling in honey bees. Proceedings of the National Academy of Sciences, 107(52), 22705-22709.
People suck. Well they certainly seem to after several nights without sleep. As the lost hours pile up, those simple things sent to try us become all the more difficult to face. We are generally just less able to employ self-control to moderate our feelings towards the outside world. I mean, it’s like Nigel Farage said to me down the pub once, we even tend to make racist comments when we’re a bit tired. Now sleep deprivation does not make you racist, despite amusing attempts to throw old Nige a bone, but it may be that a lack of shut-eye can make us less able to inhibit unconscious biases.
Unconscious biases are not necessarily a bad thing before we start to bash them. They allow us to employ speedy decision making without having to weigh up the pros and cons of a situation. When you’re faced with immediate danger you don’t want to spend time considering the difficult childhood of your knife wielding assailant for any more than a split second before you run away with your tail, and wallet, trailing behind. However, when we’re not facing a troubled mugger your conscious mind can step in and make use of available mental resources to stop yourself acting on your unconscious biases. This allows you to mask your own biases under the shield of social desirability. However, how do you assess an individual’s unconscious biases if they are unaware of them themselves?
It is possible to assess your unconscious biases by completing something called the implicit association test (IAT). This was developed by social psychologists Anthony Greenwald who wanted to try to understand the unconscious biases individuals held. They felt that explicitly asking individuals about sensitive issues was a poor way to investigate controversial topics as people would be likely to hide their true responses behind a ‘socially desirable mask’. Instead if you got people to respond very quickly to words paired with negative or positive emotions you could see how readily certain associations are recognised. For example, you could show pictures of white and black faces and pair them with positive and negative emotions. You could then present every possible combination in a randomised order (black-good, white-bad; black-bad, white-good) and see how quickly people respond to these pairings. The logic being that if you were quicker to respond to black-bad and white-good than the other pairings you, on an unconscious level, see these as more strongly related than the alternatives. Race is used here as an example but this task has been used for a wide range of different judgements such as gender and careers, weight, age and many others. You can see many of them and give the task a go here.
It should come as no surprise that sleep is considered important when it comes to our unconscious biases. Hopefully anyone who has read at least one of these posts should be aware of how many things sleep is important for. A study published in 2015 showed that by stimulating slow wave sleep (i.e. the deepest stage of our nightly slumber) you could enhance daytime training to reduce unconscious negative biases. However, it was still relatively unknown how sleep loss could influence our own hidden biases. This is not just an interesting question but an important one too when you consider that implicit biases can negatively guide our behaviour outside of our awareness.
Therefore, in a paper published last month a team from Harvard University explored this question and wanted to understand whether chronic sleep deprivation could lead to an ‘unmasking’ of negative implicit biases. More specifically, they asked: Are we more likely to express an implicit negative bias towards Muslim Arab names when we are sleep deprived?
To test this question, seventeen participants were invited into the laboratory for 25 days and it was under these strictly controlled walls that participants’ sleep was monitored. During this period, invited participants spent five days on 4 hours sleep and two days on 8 hours. This continued for a total of three weeks. The same participants, were invited back 2 months later to spend another three weeks in the laboratory but this time they could sleep for 8 hours every night. This meant that each participant served as their own control for the study. On the 21st day participants were given the implicit association test (IAT) for Muslim-Arab names and the scores during the well-rested and sleep-deprivation conditions were compared. The researchers predicted that during sleep deprivation participants would show an increased negative implicit bias towards Muslim-Arab names (i.e. they would be less able to mask their biases).
So, what did they find?
Well when participants were well-rested they did not show a negative implicit bias towards Muslim-Arab names. This is good and somewhat encouraging. However, when they were sleep deprived the same participants did show significant evidence of a negative implicit bias. That is, they more readily associated Muslim-Arab names with “bad” rather than “good”. This suggests that sleep deprivation may make us more likely to express our implicit biases.
Well before we get carried away this task is not a perfect way to assess unconscious biases and simply because our perceptions are unconsciously altered does not mean our behaviour is too. It’s also important to note that this group of participants did not have an implicit negative bias normally (e.g. when well-rested). Yet, it was possible to see that a moderate bias was found following three weeks of substantial sleep deprivation. On that note, it would be very interesting to see if in groups who already have an implicit bias show the same increase in bias following sleep deprivation and whether good sleep could reduce the negative implicit bias shown.
However, it does suggest that sleep deprivation in situations where workers have to act quickly and intuitively may bias our perceptions in a negative, and potentially fatal, way. This is particularly relevant for police officers, military personnel, and individuals working in airport security who may work long shifts and who may need to make snap judgements. We should be careful before anyone shouts from the rooftops “being sleepy makes you more racist”. This task is looking at implicit biases and the IAT do not represent explicit biases. In most instances we have the time, and resources, to make a balanced judgement. Nonetheless this research showed that a lack of sleep can negatively influence our own unconscious biases towards others. As for outright racism? A lack of sleep won’t suddenly make you racist – sorry Nige.
Alkozei, A., Killgore, W. D., Smith, R., Dailey, N. S., Bajaj, S., & Haack, M. (2017). Chronic Sleep Restriction Increases Negative Implicit Attitudes Toward Arab Muslims. Scientific Reports, 7.
When we think about increasing global temperatures we tend to think melting ice caps, flooding, and conspiracy theorists who believe scientists (or the Chinese) make this stuff up to exert some unknown power and influence. However, the temperature at night has a direct influence on the quality of our sleep too. So, I’m back to talking about sleep again (the sigh of relief from my adoring crowd is audible – thank you). A recent paper, published in Science, has shown that global warming will not just have an effect on political alliances but also on our sleep. Trump, take note.
The premise of the recent paper, by Dr Nick Obradovich and colleagues, is a simple but profound one. As the summer months trundle on by (and yes, we get some occasional sunshine here in the UK too) you are probably acutely aware of the nightly sojourn to bed and futile attempts at sleep in the oppressive heat. Unless you have the advantage of a trusty fan or even a hint of a breeze outside you know you are going to toss, turn, and throw the covers around until you eventually nod off for a few fragmented hours. Temperature has an evident ability on our ability to get to sleep. This is shown clearly when we consider the changes in body temperature throughout a typical night. As we drift off our body temperature reduces and remains lowered during the sleep period until we wake up. At this point, it starts to rise again helping to improve alertness during the day. This pattern, or circadian rhythm, is no accident – it helps to send us off to sleep. This rise and fall is important and if we increase our temperature too much (e.g. lying in a particularly stuffy room) then we delay the time at which we drop off and are more likely to wake up during the night.
It is this quirk that a research group explored in relation to global warming. In light of what we know, will the increase in global temperature negatively influence our sleep? We can assess this by looking at unseasonably hot days during a month and correlate this with the reported number of nights of poor sleep in the population. This is exactly what Obradovich and colleagues did. They assessed the temperature changes from the average in a number of cities across the US and identified the sleep habits of hundreds of thousands of respondents to a large survey assessing health and disease. They controlled for potential confounders and found that as the temperature increased from the average, for any given month, that there was an increase in reports of nights with disturbed sleep. In fact, as the temperature rises then so does the number of disturbed nights of sleep. When the group compared low and high earners and young and old populations they found that those who were poorer and older tended to suffer more from the effects of temperatures spikes. Finally, as would be expected, they found that these effects were only significant when they looked at the summer months.
This highlighted largely what we already know: that temperature negatively impacts on sleep quality by interfering with the normal process of drifting to sleep. However, the interesting point comes from the next finding of their study. They identified the predicted increases in global temperature until the end of the century from NASA. They then plugged in these values from the first part of the study to identify the effect of increasing temperatures of the number of nights sleep loss until the end of the century. Somewhat worryingly, they found that over the next century the number of nights poor sleep increases in line with the increases in temperature in part due to global warming and climate change. This has implication for physical and mental health which has consistently been tied to the quality and duration of our sleep.
It is important to note that there are plenty of caveats to this study. For example, its indirect and correlational measure of sleep and temperature should raise some concerns about the validity of the findings. Furthermore, it’s important to note that sleep was assessed with a single self-report question, “During the past 30 days, for about how many days have you felt you did not get enough rest or sleep?”. As the authors suggest, further experimental data is needed to back up their claims. However, the findings from this study do fall in line with what we already know about the effect of temperature on sleep. It is not a stretch to claim that global warming, ignoring other external factors, will have a negative impact on our sleep. There are of course ways to mitigate the negative effects of increasing global temperature but this study also accounted for that. The poorest and oldest stand to suffer most as they cannot afford to keep air conditioning running all night. Therefore, although this is one admittedly large-scale study there is still additional research which needs to further understand the true impact our warming climate will have on our sleep and subsequent health. For the time being, it raises an important reminder that the effects of global warming are far reaching and ignoring the clear evidence for its existent is nothing short of irresponsible and short-sighted. Again, take note Mr. President.
Obradovich, N., Migliorini, R., Mednick, S. C., & Fowler, J. H. (2017). Nighttime temperature and human sleep loss in a changing climate. Science Advances, 3(5), e1601555.
“Why have you stopped speaking about sleep?”
“I can have other interests!”
“I don’t know man, you’ve changed. Why should I care about anything you have to say now?”
What is a microbiome? That’s a very good question. For a start, it’s not some artificial eco-project which is attempting to save the world or even, I’m sorry to disappoint you, some form of miniaturised food either. The microbiome refers to the different ecosystems of microbes which we have all over our body. These microbes use us as their home and in turn can benefit us, live mutually alongside us, or cause us problems. They form a complex and important addition to the multitude of cells which make up our own bodies and recent estimates suggest there are as many microbial cells as there are cells which make us up. One particularly well studied microbiome requires us to get to the bowels of every one of us. Quite literally. This ecosystem is the one we find in the human gut. This microbiome has also attracted a lot of interest because of its impact on the brain known as the gut-brain axis (more of this in the next article). In general, microbiome research is still in its infancy and everyone wants a piece of it. This is likely because it seems to play an important role in a number of different mental and physical functions and there is even talk of this ecosystem containing our ‘second genome’. So, what does this all really mean and why should we care?
The ecosystem of microbes (e.g. bacteria, fungi and viruses) which live alongside us help to break down food, protect us from invaders and produce nutrients necessary for our health. One good example of the benefits of the gut microbiome is evident in looking at babies and breast milk. There is a particular group of complex sugars known as human milk oligosaccharides (HMOs) which make up a considerable amount of breast milk. However, despite their prevalence in mother’s milk babies do not have the ability to break them down. This should make them rather useless to the baby and a waste of resources for the already energy-stretched mother. Indeed, this finding initially stumped scientists as breast milk has evolved to be the perfect nutrition for an infant – why should it contain something a baby cannot digest? However, it seems that a specific HMO, B. infantis, in the infant’s gut is the intended target of this sugar instead. B. infantis can break down the complex sugar and in turn flourish in its presence. Why is this a good thing? Well it is hypothesised that the healthy colony of B. infantis force out more harmful bacteria from making their home in the infant and act as decoys for potential pathogens keen on harming the bleary eyed newborn. Moreover, this rather nifty bacterium promotes gut health and has anti-inflammatory properties. The mother’s breast milk helps ensure this positive bacterium survives and in turn the bacterium ensures the baby is more likely to survive.
How about in adulthood though? What are some of the functions of our microbiomes scattered around our body? Well the ‘second genome’ seems to play an important role in our behaviour and health. For example, in a series of experiments which looked at the effects of transferring human bacteria from obese and lean twins to germ-free mice. The researchers found that when the mice were given the bacteria from the lean twin they stayed the same weight; however, when the bacteria were from an obese twin they gained weight. This is despite the mice all being given the same amount of food to eat. Furthermore, it seems that lean mice which live together with obese mice have the capacity to transfer their ‘healthy’ microbiome. Yet, the obese mice could not transfer their bacteria to the lean mice. This, it is argued, was because the obese mice have a lower diversity of bacteria within their gut microbiome and this leaves space for new species (found in the lean mice) to colonise and flourish. The bacteria of the lean mice tend to win in these situations. However, the positive effect of the transfer of bacteria on the obese mice is not universal. It requires that the obese mice have the right diet in the first place. If the obese mice were fed a westernised diet high in junk food and saturated fats then the positive impact of the bacteria from lean mice was non-existent. The positive effect was seen only if the obese mice were eating a healthier diet from the start. It could be speculated that this is because the high-fat diet does not promote the survival of the bacteria found in the lean mice’s gut. This opens up the exciting possibility that our gut bacteria are having an important role in our weight and health. It is possible that a particular diet might be able to promote the colonisation of new species of bacteria within our microbiome and, in turn, help promote weight-loss.
The human microbiome has also been linked to illnesses characterised by disruption of the normal functioning of the immune system. It has been argued that autoimmune conditions such as crohn’s disease and ulcerative colitis may be linked to a failure of the gut microbiome to develop appropriately during childhood. It’s claimed that this is because of the increased use of antibiotics and high-fat, low-fibre, diets which characterise the western world. The presence of these environmental factors reduces the diversity of the gut microbiome and interferes with the normal process of teaching the immune system how to function. In addition, certain species of bacteria appear to have anti-inflammatory effects which researchers are trying to capitalise on as treatment possibilities for inflammatory bowel diseases (IBD).
So, it looks like the gut microbiome can have profound effects on our health. With this in mind, can we change our gut bacteria? Well, there are a lot of potential problems with this. Our gut microbiome seems to be influenced by the microbes which our mother and father impart upon us at birth (particularly from our mother). However, during infancy we go through a fluctuating development of our microbiota and the constituent microbes change considerably as we progress to adulthood. This is why some researchers believe that it is during early childhood that any attempts to modify the microbiome will be most effective. It is during this period of flux for our plucky neighbours that attempts to modify the microbiome are likely to be most effective and long-lasting. If there is a link between our gut microbiome and autoimmune disorders it is likely that this stage of our development is critical to reduce the risk of IBD. However, during adulthood there is more stability of our microbiome. The gut microbiome appears resilient to change following diet in the short-term but it is possible that long-term dietary changes might create a more favourable environment for new microbial species. For example, when the initial gut bacteria colonise an area they change the environment so it is more beneficial to their survival compared to other species. Therefore, although there is an obvious benefit to improving our diet, whether this boosts our microbiome is not quite known yet.
The human microbiome is not confined to our guts but our mouths, throats, noses, genitals and skin, to name but a few, are also examples of microbiota within the human body. For example, we contain our own signature of gut bacteria on our hands although there is considerable variation between individuals and even between our own two hands. It is not known exactly what is responsible for this variation but a mixture of genetic and environmental (e.g. hand-washing, climate, sex, etc.) factors seem to be important. It is also possible to shift the microbial constitution of someone else’s hand through direct contact – a handshake. How long the changes remain, however, is not clear and it is likely that the ecosystem carved out by your own skin microbiome favours the microbes usually residing on and in your skin. This is perhaps something to keep in mind when meeting your hero and desperately trying to shake their hand. It may be that greatness can rub off on others through a firm handshake. Also, in a similar manner to the gut microbiome, the composition of microbes on the skin has also been linked to health and disease. A good example of this is psoriasis which involves the development of plaques on the skin of those affected. In a similar manner to the gut microbiome, it is likely that a wider diversity of the skin microbiome has anti-inflammatory properties which are protective against auto-immune disorders such as psoriasis.
So, does this mean that all of us need to alter our eating habits to ensure that our gut bacteria are working at their best? Probably not for the time being. This is the nature of any research in its infancy and beware of any book or news article which claims that changing your microbiome through diet will improve your health. Despite all the excitement surrounding the microbiome at the moment we need to be aware of the limitations of research which seems to be ‘in vogue’. There is plenty of high-quality research which is being carried out in this area but much of this research is conducted in mice and the human research is largely correlational. It’s currently difficult to infer cause and effect – does poor health causes changes in our microbiome or vice-versa or, more likely, is it a mixture of the two? We need to be aware of how little we really know about the microbiome at this current moment. For example, we don’t know what a healthy microbiome looks like. Is there one individual ‘optimal’ combination of microbes to strive for or is it that a greater diversity, in general, is best? There seems to be some evidence of ‘types’ of stable microbiomes in adults but this work is still in development. There is also some evidence which links a healthier, fibre-rich, diet to a greater diversity of microbes within the gut microbiome but it is unclear what impact this has on health and behaviour. Currently, the Human Microbiome Project is trying to understand what the normal limits of the microbial ecosystems look like and how they might be implicated in health and disease. Although they started in 2008 and have received considerable funding there is still a long way to go before we see these findings directly influencing health. There is plenty of excitement about the microbiome but it is still early days for this field. For now, the human microbiome holds a plethora of secrets yet to be unlocked about the teeming, fluctuating, and enigmatic organisms we share our body with.
References / Recommended Reading:
http://hmpdacc.org/ (Human Microbiome Project Website)
http://www.newyorker.com/tech/elements/breast-feeding-the-microbiome (An extract from the amazing Ed Yong’s book, ‘I contain multitudes’)
http://www.radiolab.org/story/funky-hand-jive/ (A hilarious and brilliant podcast on this topic)
You slowly creep towards the door while being acutely aware that the slightest sound will get you caught. As you reach for the handle and steadily open the large wooden door you hear a slight creak. Suddenly, the expansive and exposed wall to your right explodes in a flurry of shrapnel, wallpaper and dust. A figure starts to emerge from the wound in the wall and stares directly at you with a terrifying smile. You’ve been found out…
Virtual reality isn’t always quite so terrifying but the above example reminds us that the virtual world has the capacity to make us believe what is thrust directly in front of us. The fear is real and the experience is one which mimics the experience of navigating a trap ridden residence. Besides terrifying us and fuelling visions of humanity being locked in a virtual world to escape the real one, what is the future of virtual reality? Well, one emerging area appears to be concerned with improving mental health.
Use of virtual reality to treat mental health difficulties
Psychosis, a cardinal symptom of schizophrenia, is the presence of delusions and hallucinations which can cause considerable distress. Delusions can take many forms and the nature of these seem to be tied to the diagnosis present (e.g. bipolar disorder, depression or schizophrenia). One delusion common to those diagnosed with schizophrenia is paranoia which can, understandably, cause significant distress and impairment in an individual’s life. However, what if we could challenge the paranoid thoughts of those experiencing psychosis and illustrate their unfounded nature? A real-world setting is likely to be too anxiety-provoking for obvious reasons but what if we could recreate paranoia-inducing environments in the relative safety of virtual reality?
This is exactly what a group at the University of Oxford led by Professor Daniel Freeman has explored in their study for the British Journal of Psychiatry last year. They exposed individuals with persecutory delusions (e.g. paranoid thoughts) to one of two mock real-life setting through virtual reality and asked them to do one of two things. One group was simply exposed to the virtual environment and asked to simply experience the situation. The effect of this on their their paranoia was assessed. The second group, by contrast, was asked to drop their guard, stop using their safety behaviours, and actively put their paranoid thoughts to the test (e.g. Do people in this environment see me as an easy target and do they actually do things to belittle me?). This second condition was known as the cognitive therapy group as they were encouraged to actively re-evaluate their delusions in the safe confines of the virtual environment.
There were 30 participants tested and they were randomised to either an exposure or cognitive therapy condition. They were tested in a real-life setting initially, then gradually introduced to the virtual reality environment, and then finally tested in the real life setting once again. At each point participants were tested before and after their immersion to either real-life or virtual reality on a scale assessing the conviction and distress of paranoid thoughts. As a test of ‘credibility’ the participants were also asked whether they believed the virtual reality setting would help them overcome their paranoid thoughts. Participants were tested in one of two different virtual reality settings. The first setting was a typical one for any Londoner: a tube journey. The second was a lift which the participant walked into and could inspect the other passengers.
So, what did they find? They found that there was a significant and large reduction in conviction and distress of delusions following the cognitive therapy group’s immersion into the virtual environments. Interestingly, these findings also carried over to the real-world setting. On average, they found a reduction in scores of around 20% for the cognitive therapy vs the exposure virtual reality condition. This suggested that getting individuals with paranoid delusions to test out their threat beliefs in a safe environment had the impact of reducing their paranoia. This should be considered in light of the difficulty to achieve this in a real life setting due to considerable anxiety and stress. This suggests that virtual reality is a simple and effective way to combat threat beliefs in paranoia.
However, this was only completed over a single day and the long-term impacts of using virtual reality is this way are currently unknown. Is there a dose-dependent effect of VR on threat beliefs? How long do the therapeutic gains last for? Are there individuals for whom this works better or worse? Are there any unintended side effects of using VR for multiple sessions in a patient population? And many other questions which remain to be answered. Psychosis is not the only field where virtual reality has started to prove its worth in treatment and research but anxiety, depression and eating disorders are also highlighted in the recent review by Professor Freeman earlier this year.
It should be noted that virtual reality is by no means only being realised within mental health but it is starting to be used extensively within physical healthcare too. VR provides an optimal way to train new surgeons, doctors, and nurses in medical procedures. This is what current research is exploring and virtual reality is only one avenue. Augmented reality is becoming more common and apps such as VR in the OR allow us to witness surgical procedures in an interactive manner from the comfort of your own home.
Basic Science and Mechanisms Research
So, there appears to be promise for using virtual reality as a way to deliver therapy but what about research more basic, mechanistic, research (e.g. what causes paranoid thinking in the first place)? Surely if we can create a convincing setting then we could start to study how threat beliefs are generated, in the case of psychosis, or understand what might reduce of exacerbate mental health difficulties in general. In an earlier study conducted in 2003, Prof. Freeman showed that paranoid thoughts could be seen in a virtual reality setting with healthy individuals. In their early foray into the use of VR they found that a small number of participants in their sample attributed hostility towards the avatars present in the environment. The researchers argued that this showed that VR could be used to study paranoia and provide a more realistic environment to test predictors of paranoia in a social setting.
Finally, because we can treat these virtual realities as realistic and convincing, they provide a great landscape in which to explore situations which might prove difficult for those at risk for certain mental illnesses. This allows researchers to test out hypotheses without unnecessarily exposing participants to a threatening situation, and with the ease of removing the headset instantly if the situation becomes distressing. For example, it would be possible to further probe the effect of sleep on mood and how this might contribute to mental health difficulties through the use of virtual reality. Now, as with any science, the worth of the study is not dependent on how flashy the toys are which are used but the strength of the research question and design. Although VR may strike some as flashy, it is useful in that it provides a way to recreate reality but in the controlled and safe confines of the lab. VR may currently be synonymous with jump scares and large price tags it is also being used to improve the health of the public. The widespread use of VR across healthcare settings is still a while off. For now, we shall just have to be content with scaring ourselves senseless with Resident Evil and other horror games.
Freeman, D., Bradley, J., Antley, A., Bourke, E., DeWeever, N., Evans, N., … & Slater, M. (2016). Virtual reality in the treatment of persecutory delusions: randomised controlled experimental study testing how to reduce delusional conviction. The British Journal of Psychiatry, 209 (1), 62-67.
Freeman, D., Reeve, S., Robinson, A., Ehlers, A., Clark, D., Spanlang, B., & Slater, M. (2017). Virtual reality in the assessment, understanding, and treatment of mental health disorders. Psychological Medicine, 1-8.
Virtual Reality (Header)
Our memory is far from perfect. You have probably gone into another room and completely forgot what you went in there for. You stare into space and hope it will come back to you. Was it to pick up keys, tidy something or speak to someone? Nope, it just doesn’t come and you walk back slightly dazed and annoyed at your ailing memory. This is just a small example of the times our memory fail us during our day-to-day lives. However, what if we could improve our memory while we sleep?
Sleep is important. I’d like to think that I’ve impressed on you all by now. It protects us from certain metabolic disorders, keeps us alert to our surroundings and maintains our mental health and overall mood. There is some evidence to suggest it helps the brain’s natural waste disposal systems but that’s still in its very early days (despite some bold claims in the mainstream media). All of these areas have garnered substantial interest from scientists but memory is the one we’ll be focusing on. Typically, studies show that our ability to lay down new memories improves after a simple nap or a good night’s sleep. This, of course, isn’t always practical but it provides us some insight into what is happening in the brain when we drift off. It also should remind anyone revising for exams that sacrificing sleep is a false economy – unless of course you need to cram. Sleep can only help you so far there.
The link between sleep and memory raises an interesting question: what is it about this period of seeming inactivity that may help improve our memory? Sleep is far from a unitary construct and if we could identify the specific stage or stages which are crucial for memory then perhaps we could capitalise on this. We go through different stages of sleep, broadly, broken down into Non-REM and REM, and these are made up of different brain cell oscillations (see picture below) within the brain. Through probing the different stages, we can start to understand which are more important for memory. So, what are some of the candidates for sleep’s role in memory? The main contenders are sleep spindles and slow wave sleep (although REM has also been claimed to play a role in memory too).
Sleep spindles are characteristic of sleep stage 2 and are brief bursts of activity seen when using a brain imaging device known as electroencephalography (EEG). Imagine one of the funny caps with electrodes protruding out as you probably have a good idea of the typically EEG setup. Sleep spindles have been claimed to be important for memory consolidation and form a key part of one of the main hypotheses for how sleep might boost our memory. More specifically, it is argued that sleep spindles may facilitate the movement of memories from temporary consolidation in a part of the brain known as the hippocampus to the rest of the brain. Interestingly, sleep spindle activity correlates with performance on memory recall following sleep, and spindles show an increase following learning. The activity location of the spindles seems to be associated with the location of brain activity engaged during intensive learning of a specific function. As a result, some have suggested that sleep spindle activity may be used as a marker for learning potential (Fogel & Smith, 2011). However, the reality is likely more complex than this. Nonetheless, it does point towards spindles as a potential marker of memory consolidation during sleep.
In addition, slow wave activity (SWA) has also been shown to be important for memory. These are the slow (1Hz) oscillations characteristic of deep sleep. It has been this stage of sleep which has primarily been targeted to improve memory in previous studies. More recently, slow wave activity and sleep spindles have been successfully modified through the use of electrical stimulation of the scalp, drugs, playing sounds throughout the night (specifically timed and not so loud as to wake the participants), and even by presenting odours present at the time words were initially memorised. These manipulations have been shown to improve memory and it seems it does this by increasing the amount of slow wave activity and sleep spindles. This work, although still in its infancy, suggests that it possible to stimulate specific features of sleep and, in turn, improve a vital cognitive function. It is at this point that a recent study in the aptly titled journal ‘Sleep’ comes in.
A group at the University of Helsinki in March this year (https://www.ncbi.nlm.nih.gov/pubmed/28364428) built on these previous findings by trying to identify a way to automate this process of stimulating slow wave activity. The success of this aim would increase the ease of introducing this technique into a home-setting and allow for the modification of sleep coveniently. The group decided to try to find a way to target sound stimuli to slow waves automatically in the hope of improving specific types of memory without affecting the sleep quality or mood of the participant. This is crucial as it is little use improving memory and modifying sleep if it causes other problems at the same time.
How did the researchers attempt to automate this process? They recorded electrical activity from the brain during sleep and were able to identify slow wave activity automatically by looking out for a specific frequency band (i.e. how often a waveform occurs over a set period of time). Whenever slow wave activity, indicative of deep sleep, was identified in the sleeping participant, a computer program sent a message to another device which played a brief sound. This meant that the sound was played just after a period of slow wave activity. Following this, there was a break of least 2 seconds between each sound being played. The loudness of the noise was changed automatically in response to cues from the participant. For example, if it seemed that the participant was waking up then the sound was lowered.
With the system in place, a total of 15 participants were invited into the lab for three days, each day separated by a week, to test out the automated approach to increase slow wave activity. The first day involved a familiarisation night so that the participants could get used to sleeping in the lab and with the equipment setup. During day two, one half of the participants heard the automated sounds and the other half did not. This was then switched for the third and final day. This allowed the researchers to compare performance on memory tasks when the sounds were not played and when they were not.
So, what did they find? Firstly, and importantly, they showed that their automated enhancement of slow wave activity was successful and viable. It managed to increase slow wave activity and sleep spindles. Moreover, the automated sounds were also found to increase memory overnight. They showed that word-pairs could be enhanced by playing a relatively quiet sound during slow wave activity. The interesting outcome of this study is that the possibility of having an automated system which people could use at home to boost memory. For populations who have poor memory this could hold promise as a therapeutic tool. It is a while off anything like this being available but it tells us something about how sleep contributes to memory and the potential ways we can exploit this in the future.
Although it is still unclear how exactly sleep is linked to memory, it is research like this which is starting to uncover that our brains are anything but quiet during sleep. Although there is likely to be no device which will improve your memory overnight on the market any time soon, scientists are working on the concepts necessary for this to become a reality. For now, perhaps you could try writing down what you’re about to do before walking into a new room?
Leminen MM, Virkkala J, Saure E, Paajanen T, Zee PC, Santostasi G, Hublin C, Müller K, Porkka-Heiskanen T, Huotilainen M, & Paunio T (2017). Enhanced Memory Consolidation Via Automatic Sound Stimulation During Non-REM Sleep. Sleep, 40 (3) PMID: 28364428
Fogel, S. M., & Smith, C. T. (2011). The function of the sleep spindle: a physiological index of intelligence and a mechanism for sleep-dependent memory consolidation. Neuroscience & Biobehavioral Reviews, 35(5), 1154-1165.
Sleeping Cat (Header)
Sleep Stages (Body Text)
What if I was to tell you that playing video games can be good for you? That despite derision and their use in political point scoring, games such as Tetris and Candy Crush could one day be used to help people deal with traumatic events in their lives? You might be initially sceptical but there is growing evidence to support this. Although not a new idea, Tetris has been shown to be useful in reducing the uncontrollable intrusions associated with a traumatic experience.
So, how can we use a video game such as Tetris to interfere with traumatic memories? Well, in much the same way that you would interfere with any memory. As you create a new memory and have converted all the constituent parts into a form which the brain can understand, it goes through a period of consolidation. That is where the memory is stored within your brain so you are able to recall it at a later point. Now if we interfere with the memory during this period of consolidation it is less likely that we will recall said memory. For example, if we can provide some competition for the neural real estate the original memory is vying for then we can weaken the strength of that original memory. It seems to be important that the type of memory is relatively specific and needs to match the original memory’s modality (e.g. a visual-spatial task needs another visual-spatial task to compete with it effectively). This is essentially where Tetris comes in. The authors argued that if both the trauma memory and Tetris rely on the same visual-spatial resources then you can reduce the intrusiveness of the initial trauma memory.
This is exactly what Emily Holmes at the University of Oxford and her collaborators found in studies conducted over the past eight years. If you ask a participant to play Tetris 30 minutes after a lab-controlled trauma induction you can reduce the impact of the traumatic memory compared to a control condition. These early studies showed that, at least in the lab, you could interfere with traumatic memories in a therapeutic way by reducing their intrusive nature. Although they were not carried out in a naturalistic setting they provided evidence that the proposed mechanism existed and could be manipulated. It is also key to keep in mind that this study showed that playing Tetris reduced specifically the intrusiveness of the traumatic memories and not the deliberate recall memory for the event. As the uncontrollable nature of the traumatic memory is a source of considerable distress in PTSD it is important that any intervention can have a targeted effect. What about evidence for the use of Tetris to deal with naturally occurring trauma outside of the lab? This is where their latest study, published in Molecular Psychiatry, last week comes into play (it’s open access so you can read the full article yourself here).
In a small-scale naturalistic study in Oxford, Emily Holmes, and colleagues at the Karolinska Institute in Sweden, examined individuals in A&E who had recently (within 6 hours) experienced a motor accident as a driver, passenger or pedestrian. They randomised 71 eligible participants to either an intervention or control condition to test the real-life application of their previous findings. In the intervention condition, participants were asked to recall the traumatic event initially and to then spend at least 10 minutes (maximum 20 minutes) playing Tetris. By contrast, the control condition asked participants to write down all the activities they carried out during their time in A&E (e.g. completing a crossword, speaking to a friend, etc.). Participants were assessed at one week and one month following either the control or intervention task. During the initial week participants were required to complete a daily diary of the number of intrusive memories they experienced which were related to the trauma (e.g. motor accident). The participants were instructed not to report “memories recalled deliberately or general verbal thoughts”. The number of intrusions provided a primary way to assess the success of the use of the intervention (memory cue and Tetris).
So, what did the researchers find? Primarily, they showed that the use of Tetris and memory recall was an effective intervention. The number of intrusions was significantly reduced in the intervention group after one week (9 intrusions on average) compared to the control condition (23 intrusions on average). Furthermore, they also found that the intervention group also reported significantly less distress after one week. However, this reduction in distress did not remain when participants were followed up after one month. To supplement this data, the authors also asked the participants about their subjective experience of using the intervention. Their reports were positive and it was apparent that they appreciated the distraction from the accident which playing Tetris offered. One participant highlighted this clearly with, “it certainly took my mind off of it at a time when I probably would have sat brooding and feeling very sorry for myself…”. Another participant, who had not played Tetris before, was keen to keep playing it following the allotted 20 minutes. The intervention thus proved to be both feasible and acceptable.
Together, these findings support the usefulness and viability of using Tetris to combat intrusive traumatic memories in a real-life setting. The reduction in the number of intrusions following a natural traumatic event (e.g. motor accident) supports the intervention and suggests it could be a low-cost, easy to administer, therapy. As the authors highlight in the paper, waiting times in A&E can be as long as 4 hours and this would be an ideal time to target individuals who have experienced a traumatic accident. As a well-tolerated, and simple, intervention it seems ideal. However, this study is simply the beginning of translating Tetris, or similar aproaches, into the realms of clinical practice. Although this trial did not show an effect on distress at a one month follow-up, a larger trial may be better suited to pick out subtle effects for longer periods of time. Furthermore, additional doses of the intervention may also prove effective as a ‘booster’ to the initial dose. As any good piece of research, this trial raises more questions and exciting avenues for further study.
Alongside the compelling results, why should we be so excited about this research? It provides clear evidence that marrying cognitive neuroscience and clinical practice are vital for progress in both fields. It is still early days for this collaborative approach but hopefully this soon blossoms into a powerful and fruitful relationship. Basic science studies can be blamed for being too distant from the disorders and clinical fields they are trying to unpick and affect. However, with a greater understanding of the mechanisms at work behind mental distress we can develop novel therapies, like the use of Tetris, to target them and help real people. Personally, that is one of the amazing things about research and one of the reasons why I fell in love with science in the first place. More work is needed to validate these findings but, at least for the time being, they provide you with a great retort to anyone who claims video games are good for nothing. To quote Emily Holmes’ original Tetris paper in 2009, “…clearly not all computer games are bad for you.”
Iyadurai, L., Blackwell, S., Meiser-Stedman, R., Watson, P., Bonsall, M., Geddes, J., Nobre, A., & Holmes, E. (2017). Preventing intrusive memories after trauma via a brief intervention involving Tetris computer game play in the emergency department: a proof-of-concept randomized controlled trial Molecular Psychiatry DOI: 10.1038/mp.2017.23
Holmes, E. A., James, E. L., Coode-Bate, T., & Deeprose, C. (2009). Can playing the computer game “Tetris” reduce the build-up of flashbacks for trauma? A proposal from cognitive science. PloS one, 4(1), e4153.
Tetris Building (Body)
Besides infancy, we don’t initially think of sleep as a big problem in childhood. Yet, a slew of recent articles have highlighted that insomnia and other sleep problems are not simply an issue of adulthood. A BBC Panorama documentary released last week commented on the surge in problems with sleep in children. Although there were a number of culprits identified for this increase in the problems with children’s sleep, one key point was technology and later exposure to artificial light.
We are all glued to our smartphones, laptops, and Fitbits. Modern artificial lighting allows us to work and entertain ourselves further into the night than natural light permits but the normality surrounding their use before bed is negatively influencing sleep. As people are educated more about the effects of technology on sleep, these issues should hopefully reduce but whether education can effect this change is uncertain. The question remains: How can we improve sleep without dragging people away from technology? One love-it or hate-it option may be camping.
Last month, a research group led by Kenneth Wright carried out two studies which examined how artificial light interferes with our natural sleep rhythms and our body’s concept of day and night. Study one assessed the sleep of participants firstly during artificial lighting and then natural lighting during the winter. The second study attempted to understand the impact of weekend camping on sleep. The researchers studied sleep by asking them to wear a watch to track movements and by tracking changes in a hormone called melatonin. Melatonin is released prior to sleep, reaches a midpoint during the first half of sleep and dips as you wake up. During the day, it is only detectable at trace levels because in the presence of light melatonin’s production is inhibited. This, in part, explains why we feel tired and want to go to bed at night rather than during the day. As a result, melatonin serves as a useful and precise marker of the internal biological night (i.e. when the body feels we should be sleeping).
The first study had participants spend a week, during winter, camping with no artificial light (e.g. torches or phones) and then a week in their normal, modern, environment which served as a baseline. Participants’ melatonin levels were measured during sleep after about 6 days of the modern environment and after 6 days of the natural light, camping, condition.
This initial study found that the internal biological night (e.g. melatonin onset, midpoint, and offset) is affected by seasonal fluctuations. Specifically, internal biological night is longer during winter and shorter during the summer. In the camping condition, melatonin onset and sleep onset were around 2 hours earlier compared to the modern, artificially lit, condition. However, melatonin offset and sleep offset were similar between camping and baseline. When comparing the winter data to previously collected summer data, the melatonin onset was earlier and melatonin offset was significantly later in the winter condition. More specifically, they showed a four-hour difference in internal biological night between winter and summer. However, there were no change in internal biological night between summer and winter offset when comparing the artificial light conditions. The modern, artificially lit, environment had extinguished the seasonal fluctuations in melatonin and sleep patterns.
The second study then went on to assess whether weekend exposure to natural light (i.e. camping) could help reduce the effects of social jet lag – the mismatch between the time you wake up during the weekday and weekend. We tend to delay our sleep during the weekend and this contributes to why it is so hard to wake up on a Monday morning. In this study, fourteen participants were first tested in their normal, artificially lit, environment and their melatonin levels during the night (onset, midpoint and offset) were assessed. Participants were then separated to a camping condition (n=9; natural light) or normal condition (n=5; artificial light).
What did they find? For the camping condition, the time at which participants went to sleep and woke up were similar between weekday and weekend. However, for the artificial light condition the onset of sleep was found to be delayed by almost 2 hours and participants woke up around an hour and a half later during the weekend compared to the weekday. People were staying up later and waking up later during the weekend presumably when they didn’t have work. Overall sleep duration and efficiency were similar across and within both groups. So, participants were not sleeping for longer under artificial light but were delaying their sleep schedule.
What about the data for internal biological night? In the camping condition, melatonin onset and midpoint were about an hour earlier during the weekend compared to weekday despite there being no changes in sleep timing. Interestingly, changes in melatonin were not only seen in the camping condition but also the modern setting. Melatonin onset, midpoint and offset were delayed by about an hour compared to the weekday for the modern, artificial light, condition. This is problematic if you have to get up earlier on the Monday morning for work and is linked to what we know as social jet lag. If you feel sleepier later and want to wake up later then you may find yourself being groggy and sleep deprived during the week.
Yet, when participants went camping over the weekend, they did not see a shift in their sleep onset or offset, and their biological night became advanced (started earlier) slightly. This suggests that weekend exposure to natural light (e.g. camping) may help diminish the negative effects of living in the current, high-paced, environment we currently have. The small sample size and short sampling period makes it hard to draw definite conclusions from this study but it does highlight that artificial lighting is having a definable impact on our sleep and the biochemistry underpinning it. It also provides some preliminary evidence of the biological impact of social jet lag.
You may, quite rightly, think that the results of this study are rather obvious: we stay up later during the weekend and our biology is going to follow suit unless we hike out to the middle of nowhere for the weekend. However, it highlighted the biological impact of our modern, well-lit, environment on our body’s internal clock. We know that using our devices before bed are generally bad for sleep but very few of us actually do anything about this. We may try to adopt better bedtime habits but this may be thwarted by technology (e.g. using a kindle to read just before bed)
Also, it is key to remember that light is not the only regulator of our sleep rhythms and in societies not exposed to artificial light the key determinant of the sleep cycle is temperature. This should make us think about not a single factor (i.e. light) but a multitude of issues may cause issues with our sleep. Interestingly, such individuals in cultures not exposed to artificial light also reported problems with insomnia but at a reduced rate than reported in modern society.
Nonetheless, light from devices, rich in low-wavelength blue-light, resets our biological clocks and inhibits the release of melatonin. As a result, we feel sleepier later even though we still have to get up at the same time and go to school, college or work. The recurrent sleep deprivation can in turn lower our mood, concentration and put us at increased risk of illness and metabolic disorders. Now, it is unlikely that the rise of childhood sleep problems can be fixed by wrenching tablets from children and throwing them out into the wilderness every Friday until Sunday. Nonetheless, we can think about what these devices are doing to our sleep – at the very least when we’re sleeping poorly to begin with.
Stothard ER, McHill AW, Depner CM, Birks BR, Moehlman TM, Ritchie HK, Guzzetti JR, Chinoy ED, LeBourgeois MK, Axelsson J, & Wright KP Jr (2017). Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend. Current biology : CB, 27 (4), 508-513 PMID: 28162893
Chang, A. M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112(4), 1232-1237.
Yetish, G., Kaplan, H., Gurven, M., Wood, B., Pontzer, H., Manger, P. R., … & Siegel, J. M. (2015). Natural sleep and its seasonal variations in three pre-industrial societies. Current Biology, 25(21), 2862-2868.