Sleep and Circadian Functioning: Critical Mechanisms in the Mood Disorders?

Sleep and Circadian Functioning: Critical Mechanisms in the Mood Disorders?
June 2, 2017 by
Sleep and Circadian Functioning: Critical Mechanisms in the Mood Disorders?

Sleep disturbances are a key feature of many mood disorders and are a key target for future research into treatment for depression and other conditions. Both lack of sleep and excessive sleep are core symptoms of depressive disorder and manic episodes, among other conditions.

60-84% of patients with major depressive disorder report symptoms of insomnia and rates of hypersomnia may be as high as 75%. In bipolar disorder, patients going through manic episodes often experience a reduced need (or ability) to sleep and an increased need for sleep during the depressive phase.

Sleep and Mood Disorders in Adolescence 

Given that adolescence is one of the most high-risk stages of life for the onset of mood disorders, studying how sleep affects people during this time is especially important.

The rapid mental and physical development during puberty means that teenagers often need a lot of sleep, but don’t often get it. During adolescence the sleep cycle is often pushed back due to teenagers socialising in the evenings and staying awake to spend time on their phones, computers of TVs into the early hours. This combined with early school starts means that many teens don’t get the sleep they need. Research has shown a link between the development of mood disorders and reduced sleep in childhood and adolescence.

Consequences of Sleep Disturbances 

Insomnia has been shown to be a risk factor for first and recurring depressive episodes and is an early warning sign of bipolar disorder. During sleep many processes take place in the brain which are vital for the proper regulation of emotions, meaning that those who miss out on good quality sleep have greater trouble interpreting and feeling emotions, which may exacerbate the onset and symptoms of mood disorders.

Sleep is also critical for optimal cognitive functioning, and deficits in sleep may explain the drop in mental ability noted in patients with depression and bipolar disorder. Sleep loss has also been linked to weight gain, potential for substance abuse and even risk of suicide.

How Do Mood Disorders Interfere With Sleep? 

Understanding how mood disorders relate to sleep deficiencies relates to various branches of psychology.

The body’s natural sleep cycle is controlled by an internal clock known as the circadian clock. One of the ways this clock is regulated is through exposure to light; low light triggers changes in brain chemistry which promote sleepiness, and high levels of light have the opposite effect.

Given that people who suffer from depression are likely to withdraw from society and remain inactive this may affect the amount of natural light they are exposed to, thus interfering with their sleep rhythms and making their sleep/wake cycle more irregular.

On a cognitive level it is well known that depression causes high levels of worry and constant rumination over negative thoughts. This inability to switch off from worries may prevent people from getting to sleep. Chemically, depression and bipolar disorder are strongly linked to abnormal levels of serotonin and dopamine, both of which are involved in the sleep cycle.

Insomnia Treatment and Mood Disorder Treatment

Treatment for insomnia has proven a good way of improving the success rates for mood disorder treatment. Using cognitive behavioural therapy for insomnia (CBT-I) alongside antidepressants significantly improved chances of the depression entering remission in one study. Given how interlinked these disorders are, effectively targeting both simultaneously is a significant breakthrough.

An interesting and currently under-used treatment for insomnia and mood disorders is light therapy. As noted above, levels of light are closely linked to the brain chemistry of sleep and waking. By controlling the amount of light a patient is exposed to it is possible to bring about a major decrease in manic or depressive symptoms.

Interestingly, as many as 40-60% of depressed or bipolar patients experience a significant short-term improvement in mood as a result of extreme sleep deprivation. Current research is looking into ways of using this effect to create longer-term improvements in mood.

Other new treatments for insomnia and mood disorders include Interpersonal and Social Rhythm Therapy, which aims to establish good sleep and wake cycles using interactions with others as a framework for regulating a healthy routine of activity and rest.


The relationship between sleep and mood disorders is highly complex and is affected by our biology, brain chemistry, thoughts and behaviour. Recent research shows exciting new ways that insomnia treatment can be used to make a significant impact in mood disorders, and future research may lead to the development of new and easy to produce treatments that could have a powerful effect on a variety of disorders.

If you struggle with either mood disorders or sleep irregularities and you want to find out more about how to treat insomnia, please write to us.

Source :

Authors: Allison G. Harvey
Journal: Annual Review of Clinical Psychology
Source Title:Sleep and Circadian Functioning: Critical Mechanisms in the Mood Disorders?
Publish Date: 7 Dec, 10