When the nights get long and the days get short, a lot of us start to feel a bit down. Psychologists call this winter-specific depression “seasonal affective disorder.” And while we may often commiserate with friends and coworkers about the winter blues, there’s actually still considerable debate among researchers as to whether S.A.D. is even a thing. Some researchers have argued that it’s nothing but “folk psychology,” but on Tuesday, scientists with the National Institutes of Mental Health explained in a Twitter conference that it’s very much a real and debilitating thing.

Matthew Rudorfer, M.D., the program chief for the NIMH Somatic Treatments Program, and David Shurtleff, Ph.D., the acting director of the National Center for Complementary and Integrative Health, answered questions from Twitter users about the disorder and how to treat it. While they didn’t address the lack of scientific consensus around S.A.D., they did address the fact that there is no single known cause.

lonely and leaning away from the light
Waning daytime hours in winter can lead some people to experience major depressive symptoms.

Despite its murky origins, S.A.D. is thought to affect six percent of the U.S. population, and it’s disproportionately reported in women. S.A.D., the researchers pointed out, can also strike in summer and interact with substance use disorders, but fortunately there are a number of promising therapies for the condition.

Rudorfer has been studying light therapy for S.A.D. for more than two decades, aiding the development of one of the most promising treatments for the condition. It may sound kind of new age-y, but it is based on a logical understanding of one very probable cause of S.A.D.: During winter, daylight hours are shorter, and scientists suspect that the increased darkness leads to changes in brain function, including an increase in the production of a serotonin carrier protein that results in lower serotonin levels; increased melatonin production, which makes people sleepier; and decreased vitamin D. While none of these particular hypotheses have been definitively proven, S.A.D. symptoms have been shown to improve when patients sit in front of a lamp that mimics the spectrum of light produced by the sun.

That being said, for some people, light therapy is simply not enough. After all, S.A.D. is not just a minor decline in mood or energy. It is characterized by major depression.

Because symptoms can be just as severe as non-seasonal depression, the NIMH scientists emphasize that treatment can include the same kinds of interventions as any other bout of major depression: Psychotropic drugs, cognitive behavioral therapy, and exercise.

Notably, the NIMH researchers note that alcohol use disorder can occur alongside S.A.D. and that perhaps, for some people, alcohol use is an attempt to cope with the symptoms of their undiagnosed seasonal depression.