People who laze around during the day are more likely to suffer from seasonal mood disorders, according to new research.
The study involving volunteers wearing activity sensors on their wrists sheds new light on how seasonal changes impact mental well-being. Mood disorders are the leading cause of “disability” worldwide, affecting millions of people – with up to 30% of those with major depression and bipolar disorder displaying a seasonal pattern of symptoms.
The phenomenon is now officially recognised but little was known about the influence of day length – known as photoperiod – and sunlight intensity, or solar insolation, on seasonal patterns in major depressive disorder and bipolar disorder.
American researchers examined the relationship between sunlight measures and objectively measured movement activity patterns to begin to understand the environmental factors driving seasonality in major depressive disorder and bipolar disorder.
The findings of the study involving volunteers from Bergen, Norway revealed links between daytime physical activity, depressed state, photoperiod and solar insolation. Study co-author Professor Sandra Rosenthal, of Vanderbilt University, Nashville, Tennessee, has suffered from bipolar disorder for 30 years.
She said: “Learning how to live with the illness means you have to develop these cues of understanding how you’re interacting with nature.”
She said her own symptoms would always worsen in autumn.
She said: “It felt like everything was going badly wrong. Then spring would come around, and I thought like I was on top of the world. It didn’t even occur to me that could be something called a pattern.
“I have come to realise that it is not the days getting longer or the days getting shorter that’s triggering the changes, it’s how fast.”
The findings of the new study showed, in particular, that more depressed states were associated with lower daytime activity.
Further results suggest that the impact of solar insolation on physical activity may differ between depressed people and those who are not.
Prof Rosenthal said: “This finding could indicate that depressed individuals exhibit an altered physiological link between energy input – i.e. solar insolation – and physical activity.
“On the other hand, it is also possible that increased sedentary behaviour results in reduced time spent outdoors and does not allow depressed people to capitalise on the benefits of sunlight exposure.
“The ability to identify mood disturbances, particularly in seasonally susceptible individuals, using passive digital biomarker data offers promise in informing next-generation predictive, personalised diagnostics in mental health.
“One of the goals of our study is to motivate the development of digital tools to assist clinicians and help affected individuals with self management of their symptoms.”
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