Circadian Rhythm Disruptions Associated With Mood Disorders, Adverse Quality of Life

Henrietta Strickland
May 16, 2018

Sticking to a normal daily rhythm - being active during the day and sleeping at night - can have more benefits than you might expect. The internal clock figures out the current time of the day by using the cues from sunlight and then transmits the information to the peripheral clocks located in the entire body.

The scientists examined people's circadian rhythms, which control functions such as sleep patterns, immune systems and the release of hormones, to measure daily rest-activity rhythms, also known as relative amplitude.

The researchers found that individuals with more circadian rhythm disruptions - defined as increased activity at night, decreased activity during the day or both - were significantly more likely to have symptoms consistent with bipolar disorder or major depression.

Body clock rhythms govern fundamental physiological and behavioural functions - from body temperatures to eating habits - in nearly all living beings.

For all participants, activity levels were measured over a seven-day period in either 2013 or 2014, and mental health proxies such as mood and cognitive functioning were measured using an online mental health questionnaire that participants filled out in 2016 or 2017.

"So we need to think about ways to help people tune in to their natural rhythms of activity and sleeping more effectively".

Prof Smith said this study is important on a global scale because "more and more people are living in urban environments that are known to increase risk of circadian disruption and, by extension, adverse mental health outcomes". Lower relative amplitude was also found to be reliably associated with greater mood instability, higher neuroticism scores, more subjective loneliness, lower happiness and health satisfaction, and slower reaction time (an indirect measure of cognitive function).

Messing with your body clock - or circadian rhythms, if you prefer long words - seriously increases your risk of mood disorders, the University of Glasgow researchers found. The authors also note that rest-activity rhythms differ between younger and older adults, so the associations between circadian rhythmicity and mental health and wellbeing may differ in younger age groups.

Writing in journal The Lancet Psychiatry, Dr Aiden Doherty, senior research fellow from the University of Oxford's Nuffield Department of Population Health, said a next step could be to carry out further research on younger people.

Professor Smith added: 'There are a lot of things people can do, especially during the winter, such as getting out of the house in the morning to get exposed to light and take exercise, so that by evening they are exhausted.

[2] Relative amplitude is the distinction, in terms of activity levels, between the active and rest periods over 24 hours.

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