Early to bed and early to rise makes a woman… less likely to develop depression according to new research. Specifically, middle-age to older women who naturally go to bed early and wake up early have lower instances of depression even after accounting for environmental factors like work schedule and light exposure.
The study, published in the Journal of Psychiatric Research, examined data from more than 32,000 female nurses to determine if there’s a link between chronotype — a fancy way of describing your preference of when to go to sleep and wake up — and mood disorders. The research found that chronotype (which is partially determined by genetics) appears to influence depression risk.
"Our results show a modest link between chronotype and depression risk. This could be related to the overlap in genetic pathways associated with chronotype and mood," lead author Céline Vetter, director of the Circadian and Sleep Epidemiology Laboratory at CU Boulder, said in a statement.
Previous research — like a 2016 study in the Annals of Translations Medicine and a 2015 study in Chronobiology International — has already shown that people who go to bed late are twice as likely to develop depression. However, these studies typically used data from a single, set point in time and only took into consideration one depression risk factor. This means that the research, though valuable, has made it difficult to determine whether depression causes people to stay up late or whether staying up late increases the risk of depression.
This new study, conducted by researchers at the University of Colorado at Boulder, followed the sleep patterns and depression symptoms of the more than 32,000 participants for four years, also taking into account additional depression risk factors like body weight, physical activity, chronic disease and night shift work. Those who reported being night owls were less likely to be married, more likely to live alone and be smokers and more likely to have erratic sleep patterns.
Even after taking all the other environmental and social factors into account, the participants who went to bed and woke up early had a 12 to 27 percent lower risk of being depressed than those who described themselves as “intermediate types” (neither being an early riser nor a night owl).
"This tells us that there might be an effect of chronotype on depression risk that is not driven by environmental and lifestyle factors," Vetter said. "Alternatively, when and how much light you get also influences chronotype, and light exposure also influences depression risk. Disentangling the contribution of light patterns and genetics on the link between chronotype and depression risk is an important next step."
But don’t worry, night owls — this doesn’t mean that you’re going to develop depression. In fact, Vetter said that anyone can lower their risk of depression by getting enough sleep, spending time outdoors, dimming the lights at night before you go to bed and getting as much daylight as possible.