"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".
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.
The study is both important and useful because it included so many people, used an objective measure of activity, and was able to take into account potential confounding factors such as age, deprivation and childhood trauma.
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. It was also associated with decreased happiness and health satisfaction, and a higher risk of reporting loneliness.
'Previous studies have identified associations between disrupted circadian rhythms and poor mental health, but these were on relatively small samples'.
Circadian rhythms are variations in physiology and behaviour that recur every 24-hours, such as the sleep-wake cycle and daily patterns of hormone release.
For the new study, an global team led by University of Glasgow psychologist Laura Lyall analysed data - taken from the UK Biobank, one of the most complete long-term health surveys ever done - on 91,105 people aged 37 to 73.
The findings show your body clock is associated with mood disorders.
A new study established a link between biological clock disruptions and increased risk for mental health issues.
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.
Dr. Daniel Smith, a professor of psychiatry from the University of Glasgow and one of the lead authors of the study, said that the lesson from the research is that not only sleep is important for a person's mental health, but also the regular rhythm of being active during the daytime and being inactive during the nighttime.
They said the findings were "consistent with suggestions that disruption of circadian rhythms is a core feature of mood disorders".
Sticking to a normal daily rhythm - being active during the day and sleeping at night - can have more benefits than you might expect.
This study adds to the evidence that good sleep at night and activity during the day is linked to better mental health.
Measurements were only taken once, so we don't know whether people's activity levels or moods changed over time.
Sleep hygiene - such as turning off screens before bed time and ensuring the bedroom is quiet, dark and cool - can help.
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.