Here’s a brief reminder not to assume everyone experiences the world the same way you do: Though you may be pumped for the sunshine-y days of summer ahead, there’s a small minority for whom summer is depressing. Seasonal affective disorder, something we typically associate with winter, happens to some people in the summer.
Like its winter twin, the summertime version of seasonal depression could be described as an exaggerated version of the way the seasons make most of us feel, according to the scientific literature. Winter depressives tend to eat a lot and sleep a lot; summer depressives, on the other hand, lose their appetite and struggle with insomnia. So it’s kind of like the pattern most brains and bodies follow — even people without these conditions feel sleepier in winter and have a harder time sleeping in the longer days of summer — but in both summer and winter depressives, it reaches a “pathological extreme,” as the authors of one of the earliest journal articles on summer depression, published in 1991, phrased it.
Summer SAD is not as common as the winter version, which itself only affects an estimated 5% of Americans, said Norman Rosenthal, a professor of psychiatry at Georgetown University School of Medicine who was part of the research team that first identified both versions of seasonal affective disorder. The summer kind is thought to account for just 10% of all SAD cases, by some estimates. And because it’s uncommon, summertime SAD has largely been overlooked by scientists who study seasonal affective disorder. “In the 25 years since it was first described, SAD has been the subject of more than one thousand studies,” writes Joseph Kasof in a 2009 paper on summer-onset depression in the Journal of Affective Disorders. “However, SAD researchers have narrowly focused on winter-SAD … very little was learned about summer-SAD.”
Consequently, scientists don’t have a good idea of how to treat summertime depression. Winter SAD can usually be managed with light box therapy — brief, daily exposure to a light that simulates daylight — since the disorder is thought to be triggered by the season’s lack of sunlight. But it’s not clear what, exactly, causes summertime depression: Is it the heat, or too much sunlight, or both? Anecdotally, at least, it seems to be the bright light. “Some of these people say things like, The light cuts through me like a knife,” Rosenthal said.