Early birds less prone to depression: Largest study yet links chronotype to mental health -- ScienceDaily
In 2009, all the participants included in the study were free of depression. When asked about their sleep patterns, 37 percent described themselves as early types, 53 percent described themselves as intermediate types, and 10 percent described themselves as evening types.
The women were followed for four years to see who developed depression.
Depression risk factors like body weight, physical activity, chronic disease, sleep duration, or night shift work were also assessed.
The researchers found that late chronotypes, or night owls, are 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 -- 27 percent lower risk of being depressed than intermediate types. Late types had a 6 percent higher risk than intermediate types ( this modest increase 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 Vetter.