Disruption to the body clock increases the risk of mood disorders and depression, a large study has confirmed.
Scientists at the University of Glasgow looked at the circadian rhythms – which control functions including sleep patterns, body temperature, our immune systems and the release of hormones – of more than 90,000 people to measure daily rest-activity rhythms, called relative amplitude.
Individuals with lower relative amplitude were found to be at greater risk of several adverse mental health outcomes, even after adjusting for confounding factors, such as age, sex, lifestyle, education and previous childhood trauma.
To decrease your risk of suffering from a mood disorder scientists recommend that you try to improve the quality of your sleep which is also known as "sleep hygiene".
- What is sleep hygiene?
The risk of being affected by mood disorders and depression is increased with what scientists call poor "sleep hygiene".
Sleep hygiene is your ability to get a good regular solid nights sleep without interruption and there are several things that can have a negative impact on it.
Using mobile phones late at night or waking in the early hours to make a cup of tea were among the bad habits that contribute to “poor sleep hygiene”, Daniel Smith, senior author of the paper, told The Times.
- How do I improve my sleep hygiene and reduce risk of mood disorders?
There are several ways to improve your ability to get a good sleep and as Mr Smith says, "it’s not just what you do at night, it’s what you do during the day".
The Sleep Foundation advises that one of the best ways to ensure you get a good night's sleep is to stop daytime naps or limit them to a maximum or 30 minutes.
Keep away from stimulants such as caffeine and nicotine when it is close to bedtime and although alcohol is known to help you fall asleep faster, it is also known to affect your sleep quality.
If you've drank alcohol before bed then the second half of your night's sleep can be affected when your body starts to process it.
The most important thing you can do to improve your night's sleep is to keep active through the day and inactive at night.
Mr Smith said: “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.”
- How important is this scientific breakthrough?
Dr Laura Lyall, the study’s lead author, said the team had found a “robust association” between disruption of circadian rhythms and mood disorders.
“Previous studies have identified associations between disrupted circadian rhythms and poor mental health, but these were on relatively small samples.”
ITV News Science Editor Tom Clarke stressed that while the study presents a link between sleep patterns and mood disorders, it does not prove a link.
He said: "Anxiety, depression, and irritability that is often associated with mood disorders can themselves lead to problems with sleep.
"It's very plausible to say that staying up late staring at a screen messes with your sleep routine, leading to poor mental health. But it could just as easily be disturbed sleep, (and possibly a desire to stare at a screen) are caused by an underlying mood disorder."
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.
Prof Smith, professor of psychiatry and senior author of the study, said: “This is an important study demonstrating a robust association between disrupted circadian rhythmicity and mood disorders.
“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.
“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.”