Body clock disruption linked to mood disorders

Disruption of daily rhythms linked to mental health problems

People with increased nighttime activity, decreased daytime activity, or both were more likely to have symptoms of major depression or bipolar disorder. "However, these are observational associations and can not tell us whether mood disorders and reduced wellbeing cause disturbed rest-activity patterns, or whether disturbed circadian rhythmicity makes people vulnerable to mood disorders and poorer wellbeing". They occur in plants, animals and throughout biology, and are fundamental for maintaining health in humans, particularly mental health and wellbeing.

The result found that those who experienced more disruption during the night were 6% to 10% more likely to be diagnosed with a mood disorder than people who followed a common cycle of being active during the day and sleeping at night. These subjects were also more likely to have reduced feelings of well-being and lower cognitive functioning, which was measured by a computer-generated test for reaction times.

"This is important globally 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".

The brain's hard-wired circadian timekeeper governs day-night cycles, influencing sleep patterns, the release of hormones and even body temperature.

Glasgow researchers analyzed data on 91,103 people from Britain between age 37 and 73 from the UK Biobank that was collected between 2013 and 2015.

Earlier research had suggested that disrupting these rhythms can adversely affect mental health, but was inconclusive: most data was self-reported, participant groups were small, and potentially data-skewing factors were not ruled out.

Messing with the natural rhythm of one's internal clock may boost the risk of developing mood problems ranging from garden-variety loneliness to severe depression and bipolar disorder, researchers said Wednesday.

Laura Lyall, the lead author of the study, said this was the largest study of its type ever conducted to identify an association between disrupted body clocks and mood disorders.

The study was funded by the Lister Institute of Preventive Medicine and published in the peer-reviewed journal The Lancet Psychiatry. In other words, the findings can not determine whether it was the disrupted internal clock which caused the mood disorder or vice versa.

This study had some limitations.

Measurements were only taken once, so we don't know whether people's activity levels or moods changed over time.

And it didn't take into account other illnesses, many of which can interfere with sleep, such as arthritis and heart disease.

"But it's not just what you do at night", he said, "it's what you do during the day - trying to be active during the day and inactive in darkness", he told.

"Especially in the winter, making sure you get out in the morning in the fresh air is just as important in getting a good night's sleep as not being on your mobile phone", said Smith.

This study raises more questions about how healthy it is to work night-time or irregular hours, and the 24-hour nature of modern life.

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