If you are a morning person, you may be at reduced risk for major depression, a new study suggests.
Several studies of the body’s circadian sleep-wake cycle have shown that being an early bird is associated with a lower risk for depression. But those studies were observational so could not prove cause and effect.
For example, people who are early birds may have other health or lifestyle behaviors that reduce their risk for depression — they may have a healthier diet, for example, exercise more, or have fewer health conditions, such as chronic pain, that are associated with depression. All these factors, and many others, could explain the decreased risk for depression, and not the fact of being an early bird. Moreover, depression itself causes sleep disturbances, so it could be that depression is a cause of being a night owl, rather than the other way around.
The new study, however, offers more compelling evidence that going to bed early and waking early may, in itself, provide protection against depression, independent of other factors. The study, published in JAMA Psychiatry, uses a research method called Mendelian randomization that helps pinpoint the cause of what may be a cause-and-effect relationship.