Be it personally or through friends or family, very few of us have escaped the devastating effects of depression, an ailment affecting more and more people yet with few effective treatments. Depression has become one of the most common illnesses in the US, according to the National Institute of Mental Health, which found that approximately 16.1 million adults experienced at least one episode of major depressive disorder in 2015. 

Women and young adults were particularly vulnerable. Most experts prescribe anti-depressants and psychological therapies, but these typically take a long time to take effect. What's more, there are many people for whom anti-depressant medication does not work. If doctors could prescribe a fast-acting treatment that applied to range of depression subtypes, it could revolutionize how we see this mental illness, alleviate suffering, and save considerable money. Targeting sleep patterns is one encouraging option. 

Research has consistently linked insomnia to the initiation, and worsening, of depression. Talking therapies for insomnia, such as cognitive behavioral therapy (CBTi), have been useful, but are another relatively slow process. Others have tried bright light therapy, where light boxes are used to try reset the body’s clocks in the absence of sufficient natural sunlight, since when we talk about sleep we also talk about the various body clocks within our cells and brain that govern sleep. These have been found faulty in numerous mental illnesses, including depression.

However, a team of researchers have recently turned their attention to a fast, powerful, and somewhat confusing alternative therapy: sleep deprivation. Its origins trace back to 1818, when the German psychiatrist Johann Christian August Heinroth suggested that sleep loss might be beneficial for depression in the short term, despite the well-known effects of long-term sleeplessness. After nearly two centuries, support for this idea is mounting, with an important caveat that we need to understand whether other factors might explain results. Extraordinary claims require extraordinary evidence.

Therefore, earlier last month, researchers at the University of Pennsylvania carried out a massive and systematic analysis of all the studies on sleep deprivation and depression. They did not include studies which used other treatments at the same time (e.g. bright light therapy), as it was hard to separate the effects of deprivation versus other treatments. The research aimed first to understand how many people responded to sleep deprivation as an anti-depressant, and then to understand whether certain factors (e.g. age or gender) could distinguish responders from non-responders.

Of 66 studies they analyzed they found that 50 percent of those who had received sleep deprivation therapy showed some reduction in their depression symptoms. Importantly, they found this "response" regardless of whether the research required individuals with depression to show a 30, 40 or over 50 percent reduction in depression symptoms to classify as responsive to the therapy. It also seemed to hold regardless of gender, age, type of depression (e.g. bipolar disorder or unipolar depression), or whether the participants were already on antidepressant medication. Unfortunately, the study does not shed any light on why sleep deprivation might alleviate depression in the short term. But it did show that sleep deprivation, in the short term, was useful in reducing symptoms and seemingly not a fluke result.

There are reasons to have caution about this finding. Most of the studies the team looked at had small sample sizes (10-20 individuals), and few used a control group who could sleep in the same laboratory. The control group is particularly important, since it's possible participants said they felt better because they thought that's what researchers wanted them to say. We can’t know for certain whether this was the case, but it seems that studies with a control group and more participants still showed positive results.

These findings, although weird, fit with our understanding of bipolar disorder – a form of depression where an individual will cycle between depressed moods and elation. Researchers such as the psychologist Thomas Wehr have long understood, with fairly robust findings, that a period of sleep deprivation can induce an episode of mania in those with bipolar disorder. Sleep loss may produce mania for the same reason, or a related one, for why sleep loss can improve the mood of someone suffering from depression.

But another puzzle remains: why then do most people feel rubbish rather than happy after a full night of sleep loss? Researchers do not know for sure, but have a few ideas. One might have to do with our body clocks. In depression, sleep scientists such as Blynn and William Bunney at the University of California argue that people's body clocks go out of synch with the normal day, so sleep deprivation creates an opportunity: sleep loss acts as a hard reset for those with depression. A problem with this hypothesis, though, is that other illnesses also struggle with circadian rhythms (e.g. schizophrenia) do not show the same effect of sleep deprivation.

Despite the wealth of research in this area, it does not mean that we have a rapid acting treatment for depression which clinicians are refusing to use. As usual, it's a bit more complicated than that. To safely sleep deprive someone, you have to bring them into a hospital setting, so that trained healthcare workers can monitor any distress and help with it. You should decidedly not try sleep deprivation at home, or recommend it to others. Sleep deprivation may boost some people's moods, but it will always lower your reaction time, alter your perception of reality, and generally reduce your ability to reason. It could be costly to administer this treatment compared to, say, antidepressant medication, and its effects can dissipate as soon as you again fall asleep. Still researchers are excited about the study, since it might be possible to extend the effect or extrapolate from it. If you pair sleep deprivation with other therapies, perhaps the positive mood-improving effect can become clinically viable over the long term.

Although this research suggests we know less than we think about sleep and mental illness, we shouldn’t rush out to lose sleep here and there as some plan to boost our mood. Before we get excited, we still need to understand more about why and how sleep relates to depression in the first place. Until then, if you want to boost your mood and your mental health, make sure you don't skip on your sleep. It's important for everyone.