Depression is a term used to encompass a range of mood disorders including bipolar depression, atypical depression among others. Depression affects over 300 million people globally, reduces quality of life and causes disability and premature mortality.
Research by the Brain and Mind Centre's youth mental health team and published in Neuroscience and Biobehavioral Reviews proposes a new subset of depression: Circadian Depression, which suggests body clock dysregulation are more than just symptoms of some depressive disorders.
Here, the paper's co-author Dr Jacob Crouse, explains how sleep-wake cycles could be a key to diagnosis and treatment for people living with depression.
Mood disorders like depression and bipolar disorder are the chronic diseases of young people - they emerge most often when people are in their teens and twenties and when they persist, they can cast a very long shadow of poor health and functioning for decades. By finding ways to intervene in the earliest phase of illness we hope to alter these trajectories.
Sleep, body clocks and depression
We know that only a fraction of people with mood disorders get access to treatment and fewer still get access to the right kind of treatment for their specific problems. To reduce this treatment gap, we are interested in zoning in on specific underlying mechanisms that are causing someone’s mood disorder, one of which we believe is dysregulation of 24-hour circadian rhythms (or “biological clocks”).
Circadian rhythms organise the timing of a very wide range of behaviours and processes related to depression and bipolar disorder, including the 24-hour sleep-wake cycle, metabolism, energy, and mood.
Most mood disorders emerge between 12 and 25 years. This is also a time when our circadian rhythms (or “biological clocks”) are naturally in flux, undergoing normal developmental changes. Often, these changes in sleep-wake cycles correct themselves but for some people these disruptions in the system, perturbations, can be a catalyst for mood disorders such as depression and bipolar disorder.
Sleep disturbances like insomnia (trouble falling asleep or staying asleep) are very common in mood disorders like depression. But we are now learning that some of these sleep-wake cycle disturbances might actually underlie certain symptoms of depression, like low energy, prolonged fatigue, and bodily symptoms like gastrointestinal problems.
Circadian rhythms aren’t just about getting enough sleep, although that’s important. They refer to the entire 24-hour sleep-wake cycle.
For example, the stereotype of teenagers sleeping late because they’re lazy is totally wrong – these changes are underpinned by biology, and we may actually be doing harm by dragging young people out of bed very early in the morning to go to school, when it is still “biological night-time” to their internal circadian rhythms.
The research also points to many areas of our lifestyles that have been affected by COVID, which we can incorporate into our daily lives to keep the sleep-wake cycle in check. For students or people who work varying hours and often experience disturbance in their sleep-wake cycles with early mornings and late nights, it’s particularly important to take care of these lifestyle factors:
The COVID-19 pandemic has affected many of the factorsthat keep our sleep-wake cycles regular and healthy. For example, these disruptions to our daily routines means that many of us were getting too little exposure to bright light during the day and too much exposure in the evening (from screens for example), both of which negatively impact sleep and circadian rhythms. Similarly, staying engaged with physical and social activity are both important for keeping our biological clocks running as they should.
Many young people who live with depression still do not improve with commonly available psychological or pharmacological treatments, and progress in early intervention has been described as a blind spot.
If our proposal is true – that disturbance in 24-hour sleep-wake cycles and the underlying body clock system is a cause of some mood disorders – then this may transform the way we treat some of these mood disorders, for example, by using tools like changing exposure to bright light, motor activity, or social activity to treat mental health problems.
We now think a strong focus on sleep-wake cycles could transform outcomes for some young people with mental health problems and Sleep could one day be part of a suite of non-drug treatments for mood disorders like depression and bipolar disorders.