Early to bed and early to rise may be the keys to being less prone to depression.
That is a key learning from one of the largest studies to explore the link between waking preferences and mood disorders.
Researchers at the University of Colorado looked at data from more than 32,000 female nurses for the study and discovered that even accounting for environmental factors such as light exposure and work schedules, chronotype (an individual’s preference for waking time) represented a mild influence for depression risk.
“This could be related to the overlap in genetic pathways associated with chronotype and mood,” said lead author Céline Vetter.
Previous studies have shown that night owls are as much as twice as likely to suffer from depression. But because those studies often used data at a single time-point and didn’t account for many other factors that influence depression risk, it has been hard to determine whether depression leads people to stay up later or a late chronotype boosts the risk of depression.
“It was unclear what was a risk factor for what,” Ms Vetter said.
To shed light on the question, researchers used data from female participants, average age 55, in the Nurses’ Health Study.
In 2009, all were free of depression. When asked about their sleep patterns, 37 per cent described themselves as “early types,” 53 per cent as “intermediate types” and 10 per cent as “evening types”.
The women were followed for four years to see who developed depression.
Depression risk factors such as body weight, physical activity, chronic disease, sleep duration and night shift work were also assessed.
The researchers found that late chronotypes, or night owls, were less likely to be married, more likely to live alone and be smokers and more likely to have erratic sleep patterns.
After accounting for these factors, they found that early risers still had a 12 to 27 per cent lower risk of being depressed than intermediate types. Late types had a six per cent higher risk than intermediate types (although this finding was not statistically significant).
“This tells us that there might be an effect of chronotype on depression risk that is not driven by environmental and lifestyle factors,” said Ms Vetter.
Research shows that our tendency to be an early bird, a night owl or somewhere in between is at least in part – 12 to 42 per cent – shaped by genetics. Some studies have already shown that specific genes that influence when we prefer to rise and sleep, also influence depression risk.
“Alternatively, when and how much light you get also influences chronotype, and light exposure also influences depression risk,” Ms Vetter said.
She stresses that while the study does suggest that chronotype is an independent risk factor for depression, it is “a small effect” and it does not mean night owls are doomed to be depressed.
Her advice to night owls who want to lower their risk?
Do your best to become an earlier bird.
Try to get enough sleep and exercise, spend time outdoors, dim the lights at night and try to get as much light by day as possible.
Are you an early bird or a night owl? Do you think your preference is genetic? Do you think waking preference could be a risk factor for depression?
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This article contains general information about health issues and is not advice. For health advice, consult your medical practitioner.
