Depression

Depression is a Whole-Body Disorder. Why Don’t We Treat It Like One?

Today marks the start of Mental Health Awareness Week in the UK. In previous years the campaign has explored the experiences of living with mental illness, social stigma and support resources. This year the focus has changed from living with illness to asking why so few of us are thriving psychologically. Why are so many of us in ‘survival mode’? It’s an approach that invites us to look at the wider factors influencing mental health on a sub-clinical level. When most of the people who experience depressive or anxious symptoms will not or cannot access treatment it is important to understand other viable and effective avenues for intervention.

This broader theme of what it means to ‘thrive’ reflects a growing appreciation that disorders such as depression are not simply ‘brain-based’ but are biological and psychological responses to social, environmental and lifestyle factors. Just a few days ago a review of 20 years of depression research concluded:

“…one thing is for sure: depression, and mental health problems in general, can no longer be seen only as disorders of the mind, or indeed only as disorders of the brain. The strong impact of the immune system on emotions and behaviour demonstrates that mental health is the health of the whole body.”

Two years ago the Lancet Psychiatry released a statement editorial highlighting that ‘nutrition is as important to psychiatry as it is to cardiology’ and advocated that nutritional status and dietary intervention should be considered when assessing a person’s mental health condition. The recent publication of the ‘SMILES’ Trial was the first study to elucidate diet as a causal factor in depression. Mood improvement in this study was not a factor of weight loss and while this particular study did not assess these parameters it is likely that the improvement was due to a reduction in systemic inflammation, as has been highlighted by a number of observational and RCT trials.

Inflammation is the immune system’s response to illness or injury, which, amongst other things, involves the release of small molecules called cytokines by immune cells. Typically, the inflammatory response is brief and begins to recede when the tissues start to heal. However, a number of stressful external factors also induce inflammation and the secretion of pro-inflammatory cytokines including: early life adversity, traumatic events, chronic work stress, poor diet, obesity and a sedentary lifestyle. When stress is sustained so is inflammation and this state of low-level chronic inflammation is implicated in a range of diseases including heart disease, Type 2 diabetes, Alzheimer’s Disease, and depression. Blood levels of inflammatory cytokines correlate with the severity of depression that patients report. In one trial non-depressed participants were injected with a substance called endotoxin, a toxin found in the cell walls of bacteria that the immune system recognises as harmful. The participants who were injected with endotoxin not only saw an increase in their levels of cytokines but reported significantly increased anxiety, depressed mood and loss of pleasure (a symptom of depression). The participants who received the placebo did not report these mood effects.

As well as improving diet, exercise has been shown to be effective in reducing levels of inflammation, improving mood and increasing the levels of a substance called BDNF. BDNF is a growth factor that promotes the growth of new brain cells, as well as protecting the ones we already have. Low levels of BDNF have long been associated with depression and other mental illness. Exercise mimics the action of antidepressants by raising levels of BDNF and improving the availability of the neurotransmitter serotonin, which is associated with good mood. Exercise has the additional benefit of improving heart health and general brain structure and function, and improving sleep (sleep disorders are a common factor in depression).  Taking a similar position to the Lancet Psychiatry report, a recent editorial in the journal General Hospital Psychiatry makes the case that the evidence for the beneficial effects of exercise on mental health is so compelling that it is time to start thinking about how to apply it as treatment.

Other lifestyle factors have also been shown to be effective in improving mental health including meditation, learning, fasting and even sauna use. Combined, these factors present us with the best cost-effective opportunity to reduce and prevent the development of depression and associated disorders. Sadly, few people will have access to this valuable information and support. Conducting a thorough assessment into what might be causing one person’s depression takes more time than the ten minutes GP’s are allotted per person. Psychological therapies are effective but can be difficult to access. Thus, antidepressant medication remains the most cost-effective treatment available in Primary Care. The problem is that rates of treatment-resistance (patients not responding to antidepressants) are increasing. The lifestyle factors outlined above provide opportunities to both improve the efficacy of standard treatments and as standalone options for those with mild-moderate symptoms.

Hopefully, this year’s campaign will make the case for considering lifestyle interventions in the treatment of depression. For my part, my clinical practice starts with a comprehensive assessment of both psychological and lifestyle factors including: work satisfaction; relationships; childhood illnesses, exercise; diet and nutrition, and sleep habits so that the client and I can come to as clear an idea as possible of what might be causing their distress and illuminate a number of areas for intervention to give us the best chance for a positive outcome.

To increase the availability of this valuable information I am launching a series on online seminars on a range of topics including Stress Management, Sleep, Nutrition and Obesity. It’s times for us to move away from a model of symptom management to one of illness prevention, and all change starts with awareness.

http://www.monumentalhealth.co.uk/seminars/

References

Dantzer, R., O'Connor, J. C., Freund, G. G, Johnson, R. W, Kelley, K. W. (2008). From inflammation to sickness and depression: when the immune system subjugates the brain. Nature Reviews Neuroscience, 9(1), 46–56. doi:10.1038/nrn2297

Ekkekakais, P. & Murri, M. B. (2017). Exercise as antidepressant treatment: Time for the transition from trials to clinic? General Hospital Psychiatry. Doi 10.1016/j.genhosppsych.2017.04.008

Miller, A. H., & Timmie, W. P. (2009). Mechanisms of Cytokine-Induced Behavioral Changes: Psychoneuroimmunology at the Translational Interface Norman Cousins Lecture. Brain, Behavior, and Immunity23(2), 149–158. http://doi.org/10.1016/j.bbi.2008.08.006

Pariante, C. M. (2017). Why are depressed patients inflamed? A reflection on 20 years of research on depression, glucocorticoid resistance and inflammation. European Neuropsychopharmacology. In press.

Sarris, J. et al. (2015). Nutritional medicine as mainstream in psychiatry. The Lancet Psychiatry, 2(3), 271-274.

Talking Mental Health Self-Care with Laura Thomas PhD.

Many of you will have watched the moving and insightful BBC documentary Mind Over Marathon, which followed 10 volunteers, each with their on mental health concern. Part of the Heads Together mental health awareness campaign, the programme followed the volunteers as they used training for the London Marathon both as a personal challenge and treatment. I have written elsewhere about the value of exercise as a mental health intervention and it is great to see it receiving more recognition for its benefits.

Laura Thomas PhD was the nutrition consultant on the programme and on the latest episode of her podcast we talk about the five pillars of mental health self-care, the role of nutrition on brain health and dinosaurs. Enjoy!

 

Treating Depression with Diet: The 'SMILES' Trial

Regular readers of this blog or anyone who follows me on Twitter for even half a day will be familiar with some of the research on lifestyle interventions for mental health. While these include sleep, exercise and creative pursuits, one of the ones that I keep coming back to is diet. I have reported on epidemiological studies that show a relationship between a consistently healthy diet and depression in the general population and in women. This research has been correlational, it shows that there is a relationship but, technically, cannot say that what causes what. It could be that depressed people are more likely to eat a poor diet. All that changed recently with the publication of a randomised controlled trial of the use of diet as a treatment of depression; The ‘SMILES’ Trial. The research was led by Professor Felice Jacka, who, if you are interested, I recommend you follow on Twitter for updates and links to similar research.  

The 67 participants in this 12-week Australian study were adults who were depressed at the time and who had a clinically defined poor diet. A poor diet was one that was low in fibre, fruit and vegetables and lean protein, and high in sweets, salty snack foods and processed meats. Some participants were receiving treatment in the form of medication, talking therapy or both.

The participants were randomly assigned to either a nutritional intervention group or a befriending control group. In the intervention group the participants had seven one-hour sessions with a registered nutritionist who provided them with personalised nutritional advice including example recipes and meal plans, and coached them around goal setting and motivation to help them to stick to the nutritional recommendations. They were encouraged to eat (servings in brackets):

  • Whole grains (5–8 servings per day);
  • Vegetables (6 per day);
  • Fruit (3 per day); 
  • Legumes/beans (3–4 per week);
  • Low-fat and unsweetened dairy foods (2–3 per day);
  • Raw and unsalted nuts (1 per day);
  • Fish (at least 2 per week);
  • Lean red meats (3–4 per week);
  • Chicken (2–3 per week);
  • Eggs (up to 6 per week); and
  • Olive oil (3 tablespoons per day).

In addition, participants were encouraged to reduce their intake of “‘extras’ foods, such as sweets, refined cereals, fried food, fast-food, processed meats and sugary drinks (no more than 3 per week). Red or white wine consumption beyond 2 standard drinks per day and all other alcohol (e.g. spirits, beer) were included within the ‘extras’ food group. Individuals were advised to select red wine preferably and only drink with meals.” They were told to eat to their appetites and not worry about trying to lose weight, so it wasn’t a ‘diet’ in the colloquial sense. Those in the social support/befriending group had seven one-hour meetings with a trained professional who talked to them about neutral subjects (i.e. not nutrition, mood or anything that might be considered therapy). Anxiety, depression and general mood were assessed at the beginning and end of the study, along with biological data such as weight, waist circumference, fasting blood glucose and cholesterol.

People in the dietary intervention group were four times more likely to be in remission (not depressed) at the end of 12 weeks than those in the befriending group. They also had reduced severity of anxiety symptoms. There was no change in BMI, blood glucose, cholesterol or physical activity within or between the groups. People were not feeling better because they had lost weight but they were definitely feeling better.

What is also interesting is an analysis called the Number Needed to Treat (NNT). The NNT is a rating of a treatment’s efficacy and describes the number of people that need to be on the treatment in order for one unwanted outcome to be prevented or avoided. So, if a (miracle) drug worked for absolutely everyone then the NNT would be 1. If, for example, a migraine treatment had an NNT of 100 then 100 people would need to be on the treatment to prevent one person having a migraine. The NNT in the SMILES Trial was four. This compares favourably to common antidepressant medication which can vary from 5-16, which is still considered effective particularly in relation to the high global rates of depression. The authors also make the point that that this nutritional intervention would also have positive outcomes for other problems that are commonly associated with depression such as heart disease, type 2 diabetes and obesity.

Crucially, the researchers also looked at the affordability of the diet and found that, on average, people adhering to the diet spent $26 less per week on food and drink than they were at the start of the study.

Of course, we have to bear in mind that this was a small study of people from a particular part of the world and it will both interesting and exciting to see the trial replicated with more participants from different ethnic backgrounds. However, it is also, I think, hugely important. It is the first study (as far as I can see) that demonstrates a direct influence of diet on depression. Depressed people who improved their diet felt better. This trial doesn’t tell us how the diet had this beneficial effect; the results were unrelated to any of the other measurements they took. My guess is that future replications will find a link to systemic inflammation and perhaps to action of the gut microbiome, but time will tell. The upshot is that improving diet in line with general guidelines (no extreme diets) had a significantly positive effect on depression. The benefit of this kind of intervention is that there are no waiting lists or side-effects, and it doesn’t have to be expensive. We eat several times a day and this research shows us that each meal provides us with a valuable opportunity to make a difference to how we feel.

Reference

Jacka, F. N., O’Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., Mohebbi, M., Castle, D., Dash, S., Mihalopoulos, C., Chatterton, M. L., Brazionis, M., Dean, O.M. Hodge, A. M. & Berk, M. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the “SMILES” trial). BMC Medicine15, 23. http://doi.org/10.1186/s12916-017-0791-y

New Year's Resolutions Worth Making: Week 2 - Food

At this time of year the word ‘diet’ is exclusively used to refer to the new 4, 8 or 12 week plan that will help you ‘drop a dress size’ or ‘blast belly fat’. In fact, when people think about the functions of food they will usually think about its role in fuelling or reshaping the body; it’s unusual for us to think about the influence of diet on brain structure and function. Even though we have an understanding that nutrients from food are important for the health of our organs, e.g. ‘eat carrots for better night vision’ and might even go as far as taking supplements to improve the condition of our skin or hair, we neglect the brain, forgetting that it too is an organ and relies on nutrients from the diet for optimal function. In fact, though your brain makes up only about 2% of your total body weight it accounts for nearly 25% of the body’s energy requirements; it has a huge nutritional demand. So, this January how about making a resolution to take better care of your brain?

A Quick Note on Omega 3s

If we took your brain out of your head, removed all the water, 60% of what was left would be fats, and especially omega 3s. Omega 3 fats are essential fats, ‘essential’ meaning they are crucial to brain function but the body is unable to synthesise them; they must be taken in through the diet. These fats are critical for the normal development of the brain.

There are three forms of omega-3: ALA, EPA and DHA. ALA is the version found in plants, things like chia seed (although they are also relative high in phytates that can reduce the absorption of important minerals) and flaxseeds. EPA and DHA are found in marine sources; oily fish and other seafood. The NHS recommends that we eat two portions of fish per week, of which one should be oily but barely anyone is achieving that intake. DHA is the most abundant essential fat in the brain and is understood to be particularly important for brain development so it is critical during pregnancy, infancy and childhood. As we age EPA comes in to its own providing a protective, anti-inflammatory action as well as supporting neurochemical synthesis and transmission. It’s actually very difficult for the body to make use of ALA; it can use it to synthesis EPA and DHA but not very efficiently and only in tiny amounts so people who avoid animal products and are unwilling to take a fish oil supplement are likely to be deficient.

Supplementation with EPA + DHA has been shown to improve memory performance(2), vocabulary and non-verbal reasoning (3) and may prevent age-related brain shrinkage (4). It may also play a preventative role in the disease course of Alzheimer’s Disease, now the leading cause of death in England and Wales (5). Older people with mild cognitive impairment who were supplemented with DHA and EPA improved their depression scores (6). Omega 3s may also play a preventative role in post-partum depression (7).

General Diet

A number of studies have shown a positive effect of a healthy diet on brain health and mood. Polyphenols are the anti-oxidant compounds found in berries, green tea, vegetables, spices and cocoa and they have been shown to have a protective effect on brain cells and can even promote the growth of new ones. Flavanols (a type of polyphenol) in cocoa can increase the flow of blood to the brain and as a result may improve cognitive functions such as attention, learning and memory (8). Consuming polyphenols can promote the production of BDNF, a protein that stimulates the growth of new brain cells (9). Low levels of BDNF in the brain have also be implicated in the development of brain disorders such as Alzheimer’s Disease, Parkinson’s, depression, bipolar disorder and schizophrenia (10). Though there is some question about exactly how polyphenols themselves may act on the brain it is a consistent and robust finding that people who consume diets high in polyphenol rich foods (leafy green and brightly coloured vegetables, berries, spices) are less likely to develop depression and age-related decline in brain function. In 2008 a plant- and omega-3-rich diet was suggested as a preventative strategy for Alzheimer’s Disease (11). More recently a large American trial tested a modified Mediterranean Diet and found that it was linked to a lowered likelihood of developing Alzheimer’s (12). A large Spanish studied that followed 15,000 people over 10 years found that, after controlling for other factors such as smoking, activity levels and BMI, those who ate the healthiest diets were up to 30% less likely to become depressed (13).

So, when we’re talking about a diet that protects the brain the evidence suggests that 500g of vegetables and fruit, 10g of dark chocolate, a small glass of red wine and four cups of green tea per day is effective, and supplemental omega-3s may also be beneficial.

Next week I’ll be talking about how exercise can change the structure and function of your brain. Until then, eat your greens!

Kx

References

1. Hamazaki, K., Harauma, A., Otaka, Y., Moriguchi, T. & Inadera, H. (2016). Serum n-3 polyunsaturated fatty acids and psychological distress in early pregnancy: Adjunct Study of Japan Environment and Children Study. Translational Psychiatry, 6, e737. doi: 10.1038/tp.2016.2

2. Yurko-Mauro K., Alexander D.D., van Elswyk M.E. (2015). Docosahexaenoic acid and adult memory: A systematic review and meta-analysis. PLoS ONE. 10:99

3. Muldoon M.F., Ryan C.M., Sheu L., Yao J.K., Conklin S.M., Manuck S.B. (2010). Serum phospholipid docosahexaenonic acid is associated with cognitive functioning during middle adulthood. Journal of Nutrition,140, 848–853. doi: 10.3945/jn.109.119578

4. Conklin S.M., Gianaros P.J., Brown S.M., Yao J.K., Hariri A.R., Manuck S.B., Muldoon M.F. Long-chain omega-3 fatty acid intake is associated positively with corticolimbic gray matter volume in healthy adults. Neurosci. Lett. 2007;421:209–212. doi: 10.1016/j.neulet.2007.04.086.

5. https://www.theguardian.com/society/2016/nov/14/dementia-and-alzheimers-leading-cause-of-death-england-and-wales

6. Sinn, N., Milte, CM., Street, S. J., Buckley, J. D., Coates, A. M., Petkov, J. & Howe, P. R. (2012). Effects of n-3 fatty acid, EPA and DHA, on depressive symptoms, quality of life, memory and executive function in older adults with mild cognitive impairment: a 6 month randomised control trial. British Journal of Nutrition, 107, 1682-1693.

7. De Vriese, S. R., Christope, A. B. & Maes, M. (2003). Lowered serum n-3 polyunsaturated fatty acid (PUFA) levels predict the occurance of post-partum depression: further evidence that lowered n-PUFAs are related to major depression. Life Science, 73, 3181-3187.

8. Lamport, D., Pal, D., Moutsiana, C., Field, D., Williams, C., Spencer, J. and Butler, L. (2015) The effect of flavanol-rich cocoa on cerebral perfusion in healthy older adults during conscious resting state: a placebo controlled, crossover, acute trial. Psychopharmacology, 232, 3227-3234.

9. Murphy, T., Dias, G. P. & Thuret, S. (2014). Effects of diet on brain plasticity in animal and human studies: Mind the gap. Neural Plasticity,  doi:  10.1155/2014/563160

10. Gomez-Pinilla, F. & Nguyen, T. T. J. (2012). Natural mood foods: The actions of polyphenols against psychiatric and cognitive disorders. Nutritional Neuroscience, 15, 127-133.

11. Kidd, P. M. (2008). Alzheimer's disease, amnestic mild cognitive impairment, and age-associated memory impairment: current understanding and progress toward integrative prevention. Alternative Medicine Review, 13, 85-115.

12. Morris, M. C., Tangney, C. C., Wang, Y., Sacks, F. M., Bennett, D. A. & Aggarwal, N. T. (2015). MIND diet associated with reduced incidence of Alzheimer’s Disease. Alzheimer’s & Dementia, 11, 1007-1014.

13. Sánchez-Villegas, A., Henríquez-Sánchez, P., Ruiz-Canela, M., Lahortiga, F., Molero, P., Toledo, E., & Martínez-González, M. (2015). A longitudinal analysis of diet quality scores and the risk of incident depression in the SUN Project. BMC Medicine, 13, 197-197.

New Year's Resolutions Worth Making: Week 1 - Sleep

The decision to embark on a New Year’s Detox is a frothy mix of nonsense and lunacy. I discuss why that is – at length – here. The TL: DR version: It’s not a real thing and will do you actual, quantifiable harm. If you want to make a manageable, sustainable improvement in your physical health this year you would be much better off taking 10,000 steps per day (1-2) and maybe delaying your breakfast by a couple of hours(3). So, for those of you who are sufficiently convinced that a ‘detox’ is a giant waste of time, energy and life I offer an alternative health resolution. I’ve compiled a list of the top five things you can do to improve your brain function and mental wellbeing in 2017 (based on non-frothy science) because there is no health without mental health. The fantastic five are: Sleep, diet/nutrition, rest/meditation, exercise, and learning. I was originally planning on creating a top ten but small, incremental changes are the ones most likely to stick so get these under your belt and you will be well on the way to a happier, healthier 2017.

Sleep

There’s supposed to be something very impressive about getting by with very little sleep. We hear urban legends about highly successful people who require only four or five hours per night. They are described as ‘superhuman’ rather than just ‘different’. Corporate law firms and big banks provide beds in their buildings and newly-qualified and graduate trainees fight it out to demonstrate how productive they can be, how much sleep deprivation they can tolerate.

But there is nothing big or clever about surviving on very little sleep. For people who are not natural short-sleepers (and maybe only 2% of the population are) poor and disturbed sleep is a serious problem. The American Centre for Disease Control and Prevention describes insufficient sleep as an ‘important public health concern’(4). According to a recent YouGov poll only half of people are happy with the amount of sleep that they get(5). Psychologically, we know that poor sleep:

  • Increases risk of depression
  • Impairs decision making, including around risk
  • Makes you more easily distracted
  • Makes you less able to adapt to a situation/adopt new strategies that might be more appropriate to the situation
  • Impairs communication and language skills
  • Makes you less able to control mood/impairs mood stability
  • Impairs insight

It has serious consequences for physical health too and poor sleep is associated with increased risk of obesity and heart disease(6).

For a long time disturbed sleep was seen just as a symptom of depression but more recently researchers have been looking at poor sleep as a causal factor in depressive illness(7-8). This perspective presents us with the opportunity to target sleep disorders as a treatment for depression. So, what can you do?

  • Keep cool – Cooling body temperature is a physiological indicator that it will soon be time to sleep. If your room or bed are very hot this can make it harder to drop off and impair sleep quality (think of those hot summer nights). Use the right tog duvet for the season, and use a quiet fan if you need to. You can also promote this sleep-inducing effect by taking a warm bath about an hour before bed, the cooling of the body once you step out of the bath can help to promote sleep.
  • Step in to the light - We all have a natural sleep-wake cycle that coordinates – based on light-exposure – to the 24hr day/night cycle. This is part of the circadian rhythm. Left to its own devices this cycle can drift slightly; it needs light at the right times of day to stay 'anchored'. Try to get at least 30 minutes of bright daylight in the morning or at lunchtime. A half hour walk after lunch is perfect if you can manage it.
  • Hack your ultradian rhythm - As well as the 24hr rhythm you also have a shorter, 90 min cycle clicking over throughout the day, your ultradian rhythm, and tracking this can help you to identify when is the best time for you to go to bed. The ultradian rhythm is remarkably consistent making it a very useful measure and you can track it by timing your yawns. See the image on this page. At the peak of the wave you are at your most alert and this is a great time to work through your to-do list or focus on a challenging problem. 45 minutes later you are at the trough of the wave, at your most sleepy and most likely to yawn. So, if I yawn at 7pm but it’s too early for me to go to bed, I know that I am likely to be most sleepy again at 8.30pm, 10pm and 11.30pm. I might plan, then to be in bed by 10pm or 11.30pm in order to get to sleep quickly.
  • Put down your phone – Smartphones, tablets and computer screens emit blue light. This is the same wavelength as dawn light, and this is received by the suprachiasmatic nucleus (the brain region responsible for controlling the circadian rhythm) as a message that it is time to wake up, be alert and get active. Try to avoid using these devices for at least 60 minutes before heading to bed, or, if you absolutely must, download an app that can help to filter out the blue light.
  • Make sure the room is as dark and quiet as possible (unless that freaks you out). Think about using eye masks, blackout curtains and ear plugs if you live in or near a noisy environment.
  • Avoid alcohol before bedtime – Although it can promote the initial falling asleep, alcohol disturbs the quality of sleep, preventing your brain from entering the deeper sleep stages.
  • Try not to drink too much before going to bed – I mean just normal drinks here. It seems obvious but a lot of people underestimate how detrimental midnight trips to the loo are to a good night’s sleep. Have a bottle of water by your bedside so you can rehydrate in morning.

Also, remember that here is no magic number. The right amount of sleep is the amount that is enough for you, for you not to feel excessively sleepy during the day. That might be seven hours, that might be nine, we all have different sleep needs. So, work out what is right for you and try to achieve that more often than not.

Next week, the effect of nutrition on brain function. Until then, wishing you a very restful night.

Kx

 

References

  1. Yuenyongchaiyat, K. (2016). Effects of 10,000 steps a day on physical and mental health in overweight participants in a community setting: A preliminary study. Brazilian Journal of Physical Therapy.
  2. Castres, I., Tourny, C., Lemaitre, F. & Coquart., J. (2016). Impact of a walking program of 10,000 steps per day and dietary counseling on health-related quality of life, energy expenditure and anthropometric parameters in obese subjects. Journl of Endocrinological Investgation, DOI: 10.1007/s40618-016-0530-9.
  3. Horne, BD., Muhlestein, J. B. & Anderson, J. L. (2015). Health effects on intermittent fasting: hormesis or harm? A systematic review. American Journal of Clinical Nutrition, 102, 464-470.
  4. https://www.cdc.gov/features/dssleep/
  5. http://cdn.yougov.com/cumulus_uploads/document/bt915di765/YG-Archive-140520-Sleep.pdf
  6. Kecklund, G. & Axelsson, J. (2016). Health consequences of shift work and poor sleep. British Journal of Medicine, 355, i5210.
  7. Chen, Y., Keller, J. K., Kang, J., Hsieh, H. & Lin, H. (2013). Obstructive sleep apnea and subsequent risk of depressive disorder: A population-based follow up study. Journal of Clinical Sleep Medicine, 15, 417-423.
  8. Roberts, R. E. & Duong, H. T. (2014). The prospective association between sleep deprivation and depression in adolescents. Sleep, 37, 239-244.