Understanding the relationship between our sleep, our biological clock and our mental health

Problems with our sleep and internal body clock can trigger or worsen a range of psychiatric disorders, according to a new review of recent research findings.

The review, published today in Proceedings of the National Academy of Sciencessuggests that a better understanding of the relationship between sleep, circadian rhythms and mental health could unlock new holistic treatments to alleviate mental health problems.

“Sleep and circadian rhythm disorders are the rule rather than the exception across all categories of psychiatric disorders,” says Dr. Sarah L. Chellappa of the University of Southampton, lead author of the review. “Sleep disorders, such as insomnia, are well understood in the development and maintenance of psychiatric disorders, but our understanding of circadian disruptions lags behind.

“It is important to understand how these factors interact so that we can develop and apply circadian sleep interventions that benefit patients’ sleep and mental health symptoms.”

An international team of researchers from the University of Southampton, Kings College London, Stanford University and other institutions explored recent evidence on sleep and circadian factors, focusing on adolescents and young people. young adults suffering from psychiatric disorders. This is a time when people are at greatest risk of developing mental health disorders and when disruptions to sleep and circadian rhythms are likely to occur.

Insomnia is more common in people with mental health disorders than in the general population – during remissions, acute episodes and especially early in psychosis, where difficulty falling and staying asleep affects more than half of the individuals. About a quarter to a third of people with mood disorders have both insomnia and hypersomnia, where patients have trouble sleeping at night but are sleepier during the day. Similar proportions of people with psychosis experience this combination of sleep disorders.

Meanwhile, the few studies investigating circadian sleep-wake disorder (CRSWD) suggest that 32% of patients with bipolar disorder fall asleep and wake up later than usual (a condition called sleep-wake disorder). delayed sleep). Biological clock processes (such as endogenous cortisol rhythms) have been reported to run seven hours ahead during manic episodes and four to five hours behind during the depressive phase. The timing is normalized in case of successful treatment.

What are the mechanisms?

Researchers have examined possible mechanisms underlying sleep and circadian rhythm disruptions in psychiatric disorders. During adolescence, physiological changes in the way we sleep combine with behavioral changes, such as staying up later, sleeping less on school nights, and sleeping longer on weekends.

Dr Nicholas Meyer, from King’s College London, who co-led the study, said: “This variability in sleep duration and timing can lead to a misalignment between our body clock and our sleep-wake rhythms and increase the risk of sleep disorders. and negative mental health outcomes.

Researchers also studied the role of genes, light exposure, neuroplasticity and other possible factors. People with a genetic predisposition to a reduced change in activity levels between resting and waking phases are more likely to suffer from depression, mood instability, and neuroticism.

Population-level surveys show that self-reported time spent outdoors was associated with a lower likelihood of mood disorders. Sleep is thought to play a key role in how the brain forms new neural connections and processes emotional memories.

New treatments

Dr Renske Lok, from Stanford University, who co-led the study, said: “Targeting risk factors related to sleep and circadian risk factors presents the opportunity to develop new preventative and new therapies. Some of these are population-level considerations, such as the timing of the start of the school year. and work days, or changes in the built environment to optimize light exposure. Others are personalized interventions tailored to individual circadian parameters.

Cognitive behavioral therapy for insomnia (CBT-I) has been shown to reduce symptoms of anxiety and depression, as well as symptoms of trauma in people with PTSD.

In unipolar and bipolar depression, light therapy (administered upon rising in the morning) has been shown to be effective compared to a placebo. Using it in combination with medications has also been shown to be more effective than using medications alone. Other findings suggest that light is effective in treating perinatal depression.

Timing of medications, meals and exercise could also impact circadian phases. Taking melatonin in the evening may help people with delayed sleep-wake phase disorder shift their body clock toward a more conventional sleep pattern and may have beneficial effects in comorbid psychiatric disorders.

Working night shifts can harm mental health, but eating during the day rather than at night could help, with research showing that eating during the day prevents mood disorders.

The analysis also highlights innovative multicomponent interventions, such as the Transdiagnostic Intervention for Sleep and Circadian Dysfunction (Trans-C). This combines modules that address different aspects of sleep and circadian rhythms into a sleep health framework that applies to a range of mental health disorders.

Dr Chellappa said: “Collectively, mental health research is poised to take advantage of extraordinary advances in the science of sleep and circadian rhythm and translate them into better understanding and treatment of psychiatric disorders. »