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, May 16.
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.
This study is the first to objectively measure patterns of rest and activity (using accelerometers), and to have sufficient sample size to assess the effect of circadian disruption on various mental health disorders. "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".
It is already known that the internal body clock regulates many functions including body temperature and eating habits. Disruption to these rhythms has been shown to profoundly affect human health.
Regarding the research, he told: "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".
Researchers of this study analyzed activity data from 91,105 participants (aged, 37-73 years) from the UK Biobank general population cohort to obtain the relative amplitude of the study population (a variable to determine the degree to which circadian rhythms of rest-activity cycles is disrupted).
To record their levels of activity, participants wore accelerometers for 7 days between 2013 and 2015. This information was linked to mental health questionnaires to assess symptoms of mental disorders and subjective wellbeing and cognitive function.
The researchers found that lower relative amplitude was associated with a greater odds of reporting lifetime history of major depression or bipolar disorder. It was also associated with greater mood instability (OR, 1.02; 95% CI 1.01-1.04), higher neuroticism scores (incident rate ratio, 1.01; 95% CI 1.01-1.02), more subjective loneliness (OR, 1.09; 95% CI, 1.07-1.11), lower happiness (OR, 0.91; 95% CI, 0.90-0.93), lower health satisfaction (OR, 0.90; 95% CI, 0.89-0.91), and slower reaction times (linear regression coefficient, 1.75; 95% CI, 1.05-2.45).
"While our findings can't tell us about the direction of causality, they reinforce the idea that mood disorders are associated with disturbed circadian rhythms, and we provide evidence that altered rest-activity rhythms are also linked to worse subjective wellbeing and cognitive ability", says Dr Lyall".
"The study is cross-sectional and therefore can not provide insights on causality", noted Aiden Doherty, PhD, of the Li Ka Shing Centre for Health Information and Discovery at the University of Oxford, writing in an accompanying commentary and asking: "Does circadian disruption cause a decline in mental health status or vice versa, or are both due to some third factor?"
He added: "The circadian system undergoes developmental changes during adolescence, which is also a common time for the onset of mood disorders".
"It might be that the UK Biobank provides the impetus for a resource of a similar scale in adolescents and younger adults to help transform our understanding of the causes and consequences, prevention and treatment of mental health disorders".
The study was funded by the Lister Institute of Preventive Medicine.