Cover Image - Why Sleep & Circadian Rhythms Matter For Mental Health

Why Sleep & Circadian Rhythms Matter For Mental Health

By Sarah L. Chellappa, MD., MPH., PhD.

University of Cologne, Cologne, Germany

The Importance of Sleep

Our health and emotional wellbeing matter. To ensure health and happiness, we need healthy sleep habits, as sleep and mental health are intertwined. During sleep, our body promotes tissue repair, releasing hormones for supporting growth and maintaining healthy brain function. The consequences of poor sleep are plentiful, including challenges to concentrate, to be alert and to regulate emotional responses. Many people with neurodiversity experience reduced ability to concentrate in everyday tasks, changes in their emotional responses (e.g., experiencing more anxious and depressive mood states), and in the ability to socialize, when they do not have good sleep quality.

What happens when we are asleep? Our body cycles multiple times throughout a typical night, in different stages of sleep. There are two types of sleep: Rapid Eye Movement (REM) and non–Rapid Eye Movement (NREM). During a typical night sleep, we cycle between these two broad types of sleep, with more NREM sleep (a hallmark of sleep intensity) during the beginning of the night and more REM sleep during the early morning hours, when we experience vivid dreaming. Although it remains unclear which sleep stages are differentially affected in neurodiverse conditions, there is evidence for alterations in sleep onset (i.e., the ability to fall asleep) and sleep maintenance (i.e., the ability to stay asleep). Importantly, this can result in poor sleep quality that can hinder quality of life. One possible explanation for such sleep challenges in people with neurodiversity is a disruption of circadian rhythms.

Circadian Rhythms

Circadian rhythms correspond to the daily rhythms of the body, and these are critical for health and wellbeing. We have circadian rhythms at the cellular level all the way to the system level, which encompasses our mood perception and brain activity. These rhythms have a ~24-h cycle that synchronizes to the daily 24-h light/dark cycle. Importantly, health hazards can occur when there is a disruption of these typical biological rhythms.

The Role of Melatonin

Melatonin is a hormone produced in the brain’s pineal gland synthesized mostly at night and which is crucial to circadian rhythm regulation, including sleep–wake cycles and neuroendocrine and body temperature rhythms. Nighttime melatonin levels are typically ~3-fold higher as compared to the daytime, and show peak levels in the middle of the biological night. Melatonin has many functions, one of which is the promotion of sleep. There is growing evidence that people with specific neurodiverse conditions, such as autism spectrum disorder or attention-deficit hyperactivity disorder, show a deficit in melatonin production at night, and such reduction in melatonin levels may be associated with e.g., poor sleep quality, decreased mood levels and reduced ability (or need) for socialization.

Improving Your Sleep

On the bright side, there are simple, yet effective behavioral strategies that can boost circadian rhythms, with the potential to improve both sleep quality and mental health.

Recent research has found that exposure to bright light at night (particularly exposure to the “blue” spectrum of light) can reduce melatonin levels and therefore may negatively affect circadian rhythms. “Blue” light can be found in many of the common electronic devices we have at home, such as tablets, mobile phones, computers and TV screens. Therefore, to maintain healthy circadian rhythms, it is best to expose ourselves to daytime light and avoid light at night. Inexpensive devices can be used to block out light and noise at night. For instance, eyeshades and earplugs have been associated with improved REM sleep and increased melatonin release. Moreover, some apps can partially reduce the amount of “blue light” that impinges onto the eyes. Because they do not fully block “blue” light, it is best to avoid or at least minimize the use of electronic devices 3-4 h before bedtime.

Lastly, a myriad of lifestyle factors including regular (morning) exercise and healthy diet (with meals consumed earlier in the day) have the potential to improve sleep quality, boost circadian rhythms and, in turn, improve emotional wellbeing.

Simple lifestyle choices that ensure optimal sleep and circadian rhythms can be a deal breaker for a healthy and happy life.

Sarah L. Chellappa, MD., MPH., PhD., is an Alexander Von Humboldt Experienced Fellow at the Department of Nuclear Medicine, University of Cologne, Germany. Dr. Chellappa´s work has shown that sleep and circadian rhythms affect mood, cognition and brain activity in a variety of human populations, including young and older adults, shift workers, patients with depression, with ocular diseases and with neurodegeneration. Her work combines multimodal neuroimaging approaches to assess how sleep and circadian rhythms affect brain activity that modulate mood and cognition. Her work also includes sleep/circadian interventions (e.g., light therapy, meal timing) to help improve mood, health and well-being.