GETTYIndividuals with lower relative amplitude were found to be at greater risk of several adverse mental
16 May, 2018, 22:47
The researchers found that lower relative amplitude was associated with a greater odds of reporting lifetime history of major depression or bipolar disorder (adjusted odds ratio 1.06 and 1.11; table 2). "I don't think it's unreasonable to say this is another piece of evidence that might suggest we should all be more mindful of our natural rhythms of activity and rest", Professor Smith explained.
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 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.
However, the results do not reveal whether the disruption causes mental illness, or if it's a symptom of it, as shifts in energy levels and sleep disturbances are common with a diagnosis of depression or bipolar disorder. They were also more likely to have decreased feelings of well-being and to have reduced cognitive functioning, based on a computer-generated reaction time test.
"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 big question is exactly how this link works and what "direction" it's travelling in: does poor sleep and sluggish activity during the day affect people's mental health, increasing their chances of mood disorders, or do mood disorders affect people's ability to sleep well and be active during the day?
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.
Those who are inactive during the day and more active or restless at night have an increased risk of depression, bipolar disorder and low mood.
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 work was funded by a Lister Prize Fellowship to Professor Smith.
The study can not say conclusively that body clock disturbances are what caused the mental risk, instead of the other way round.
"It's widely known that a good night's sleep is a good thing for well-being and health".
"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.
Measurements were only taken once, so we don't know whether people's activity levels or moods changed over time.
'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'.
Some researchers believe modern life may be the reason for this trigger.