On three afternoons this March, Rhiannon Phillips, a Behavioural Scientist with our multidisciplinary behavioural science team, HRW Shift, attended the Virtual Brainstorms Festival—an online celebration of neuroscience and AI and an investigation of the roles that brains, money and machines play in our lives. There was one talk in particular that captured Rhiannon’s attention…

A host of fascinating talks were sprinkled across the festival’s three days. In one, Dr. Melanie Schranz described the potential of artificial swarm intelligence (think Black Mirror and the robotic bees episode—though fortunately less dystopian and scary). She painted a thrilling futuristic picture, one in which drones will dive underwater to repair ships and zip to disaster sites to sift through rubble. Debates were held exploring the ethical implications of modern technology. Who should own the data from the smartphone apps and the wearable tech devices that are rapidly approaching ubiquity? And what are the implications for the haves and have-nots as the wealth gap continues to widen?

Unfortunately, there isn’t enough time to discuss each of these talks in depth, so, for the rest of the article, I’ll turn my attention to a particularly fascinating one—a presentation from Professor of Circadian Neuroscience, Russell Foster, on the importance of sleep as well as its exciting potential to shape the way we think about mental health.


Sleep, cognitive functioning and memory


It’s safe to say that most of us agree on the importance of sleep. After all, we do spend around one-third of our lives sleeping, so it must be up to something useful, right? More to the point, we’ve all struggled through the debilitating effects of a restless night at one point or another, and, are therefore well-aware that sleep is essential if we want to perform at the top of our game. But what about those select few who consider themselves immune from the detrimental effects of sleep-deprivation. We’ve all encountered those “ultra-productive” people who cheerfully remind us that “they’ll sleep when they’re dead!” Is it possible that they are onto something and sleep is largely a waste of time or a convenient excuse for laziness? Let’s take a tour through some recent research to find out!

In one study exploring the effect of sleep on cognitive functioning (Wagner et al 2006), three groups of participants received the same problem-solving task but were asked to complete it at different times.

  • Group 1 were introduced to the task in the morning and completed it the same afternoon. A measly 20% of the participants were able to solve the problem.
  • Group 2 were introduced to the task in the morning. They were then kept awake all night and asked to complete the task the following afternoon. Again, only 20% succeeded.
  • The final group were introduced to the task in the morning, slept normally that night, and then completed the task the following afternoon. Amazingly, 60% of this group successfully solved the problem!

A second study probed the nature of the relationship between memory and sleep (Walker & Stickgold 2006). Two groups were presented with a list of words that they would be asked to recall the following day. The list contained positive words (love, happiness, joy), negative words (crime, hate, war) and neutral words (cotton). The night before the memory test, one group slept normally (the well-rested), while the other was kept awake (the sleep-deprived). As you might have guessed, the sleep-deprived group recalled fewer words overall.

But that doesn’t tell the whole story.

The startling twist arose when researchers examined participant recall by word-type (positive, neutral, or negative). While the well-rested participants were best at remembering positive words, the sleep-deprived participants actually recalled negative words at the highest rate (a whopping 81%). To thicken the plot, the words that were most difficult for sleep-deprived participants to place were actually the positive ones.

In short, not only were sleep-deprived participants better at remembering negative words, they were worse at remembering positive ones. All of this evidence points to a single frightening conclusion—sleep deprivation leads to negative thinking. Or, more optimistically—sleep fosters positive thinking by shielding us from negative thoughts.


The relationship between sleep and mental illness


Though recognising sleep as a common challenge for patients with a variety of mental health conditions in and of itself, it seems the notion of sleep as a potential treatment pathway for those conditions has remained elusive and slipped under the radar of mental health professionals for far too long.

But cutting-edge research has gone a long way in illuminating its relationship with mental health. Sleep, it seems, is more than a way to charge our batteries after a long day; it is an indispensable and underappreciated stronghold of mental health.

Lack of sleep in the short term can result in irritability, poor attention, lack of motivation, loss of empathy, and a general bias toward negativity. The long-term health risks of sleep-deprivation can be similarly devastating—a hideous array ranging from cancer to cardiovascular disease and diabetes. So, next time someone tells you, “I’ll sleep when I’m dead”, feel free to respond, “then I guess you’ll be well-rested sooner than I thought.”

It is evident that sleep-deprivation undermines physical health, but what about mental health? It turns out poor sleep—which can take the form of excessive sleeping, insomnia, or generally disrupted sleep patterns—is a hallmark of a variety of mental illnesses. Interestingly, the same genes which regulate our natural “feel good” chemicals (such as serotonin and dopamine), also support healthy sleep patterns and stable circadian rhythms. This means that poor sleep and mental illness exacerbate each other in a vicious feedback loop. Poor sleep makes us more vulnerable to mental illness in the first place, and—once mental illness has taken hold—intensifies its symptoms; depression, anxiety, mood-instability, hallucinations, and paranoia all thrive under such conditions. In turn, when we are under the siege of mental illness, sleep can be especially difficult to come by. So, sleep takes another hit, which in turn aggravates our mental illness, and so on—the cycle continues to spin further and further into the depths.


Sleep as therapy


On the bright side, the combustive relationship between mental illness and sleep-deprivation can be leveraged for the good. A fundamental understanding of the nature of sleep and its entanglement with mental health can pave the way for new avenues of treatment.

Consider, for instance, the research exploring the ways in which improved sleep can reduce certain symptoms of mental illness. In one study, Freeman et al (2017) recruited insomniacs who reported experiencing hallucinations and paranoia. Over 22 weeks, the researchers administered a digital Cognitive Behavioural Therapy (CBT) package aimed at alleviating the participant’s insomnia.  The results were encouraging—not only did sleep improve, but the paranoia and hallucinations followed suit. Of course, any statistics student can tell you that correlation doesn’t prove causation, but the results are highly suggestive of sleep-deprivation playing a causal role in the uptick of mental illness and its symptoms.

Another study tackled the relationship between sleep and depression. But instead of CBT, these researchers used “light therapy” as a way of regulating participant’s sleep/wake patterns (Lam et al 2016). Participants undergoing light therapy exposed themselves to a lamp emitting a special fluorescent white light for a half hour every morning. The rationale behind this therapy is that white light is thought to affect brain chemicals linked to mood and sleep.

To test the efficacy of light therapy as a treatment for depression, participants were split into 4 groups.

  • Group 1 received a placebo (placebo group),
  • Group 2 received Prozac drug therapy (Prozac group)
  • Group 3 received light therapy (light therapy group)
  • Group 4 received light therapy and Prozac (light therapy + Prozac group).

After 8 weeks, 29% of participants in the Prozac group and 50% of participants in the light therapy group were sleeping better and feeling less depressed. But the clear winners were those in the light therapy + Prozac group, who displayed a remarkable 76% improvement in sleep and depression!

More research needs to be conducted, but one possible takeaway is the potential for light therapy to be used as a treatment for a range of mental illnesses. The immense potential of light therapy—as well as other sleep-focused therapies—to treat conditions such as schizophrenia, bipolar disorder, anxiety disorder, and post-traumatic stress disorder, is truly dizzying.

All in all, Foster’s talk opened my eyes to an exciting new treatment landscape, and I’m keen to see how this space develops. I hope you are as well!



Freeman, D., Sheaves, B., Goodwin, G. M., Yu, L. M., Nickless, A., Harrison, P. J., … & Espie, C. A. (2017). The effects of improving sleep on mental health (OASIS): a randomised controlled trial with mediation analysis. The Lancet Psychiatry4(10), 749-758.

Lam, R. W., Levitt, A. J., Levitan, R. D., Michalak, E. E., Cheung, A. H., Morehouse, R., … & Tam, E. M. (2016). Efficacy of bright light treatment, fluoxetine, and the combination in patients with nonseasonal major depressive disorder: a randomized clinical trial. JAMA psychiatry73(1), 56-63.

Wagner, U., Gais, S., Haider, H., Verleger, R., & Born, J. (2004). Sleep inspires insight. Nature427(6972), 352-355.

Walker, M. P., & Stickgold, R. (2006). Sleep, memory, and plasticity. Annu. Rev. Psychol.57, 139-166.


By Rhiannon Phillips

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