"To look at this in more detail, it will be useful for future studies to track participants' rest-activity patterns over time to see whether disturbed rhythms can predict whether someone is more likely to go on to develop a mood disorder", commented author Dr Laura Lyall from the University of Glasgow.
The study in "The Lancet Psychiatry" found people who sleep less at night and more in the daytime are more likely to have symptoms of bipolar disorder or major depression. Such individuals were also more likely to feel unhappy, lonely and unsatisfied with their health, and have slower reaction times.
"So we need to think about ways to help people tune in to their natural rhythms of activity and sleeping more effectively".
If you're scrolling on your phone past 10pm at night, you might be heightening your risk of mood disorders.
That is the finding from a study of more than 90,000 people by scientists at the University of Glasgow.
"Previous studies have identified associations between disrupted circadian rhythms and poor mental health, however, these were on relatively small samples".
He also told that a 10 pm cut-off will give the average adult time to wind down before switching off the lights and going to beauty sleep.
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.
Around one in 25 participants were about as active during the day as they were at night.
"It's a cross-sectional study, so we can't say anything about cause and effect or what came first, the mood disorder or the circadian disruption", said Kristen Knutson, associate professor of neurology at Northwestern's Feinberg School of Medicine, who was not involved in the study.
"The next step will be to identify the mechanisms by which genetic and environmental causes of circadian disruption interact to increase an individual's risk of depression and bipolar disorder". Circadian rhythms occur in plants, animals and throughout biology.
But as per the study, the most harmful effect of having a disrupted internal body clock is a risk of mental disorders.
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. Those with lower relative amplitude were at greater risk of mental health problems regardless of age, sex, lifestyle, education and previous childhood trauma.