Seasonal affective disorder isn’t just for winter
Researchers try to pinpoint what triggers less common counterpart summer SAD
This is what happens to the Earth during summer: Tilted about 23.5 degrees, it arrives at a place in its orbit where the Northern Hemisphere leans toward the sun. This is what happens in Wisconsin during summer: People go outside, maybe to picnics or parks, to barbecues, on day trips, on summer vacation.
This is what happens to Kristen Ashly during summer: Depression descends like a heavy curtain. She skips picnics, day trips and vacations — the hot, humid days in central Wisconsin make her lethargic, yet also agitated, irritable and unable to sleep.
It’s hard to explain the feeling to those around her, said Ashly, a wrestling journalist and an owner of the women’s wrestling website, Bell To Belles. “People who love summer, they don’t get it,” she said.
Ashly has summer seasonal affective disorder, a less common and much less understood counterpart to seasonal affective disorder, or SAD, a recurring pattern of depression that comes on in fall and winter.
A team of researchers led by the psychiatrist Norman E. Rosenthal first described seasonal affective disorder in the scientific literature in 1984. About 5% of adults in the U.S. may experience the most extreme version of the condition, which significantly alters their day-to-day life. More people experience a milder version, the “winter blues.” The shorter days of fall and winter, which can be stingy with their sunlight, are thought to be a trigger.
Often, when Rosenthal talked about his research, someone would approach him to say that the same thing happened to them — but in the summer. In 1987, he and his colleagues published a report of 12 people who experienced a pattern of seasonal depression between March and October. This and subsequent work suggested that summer SAD presented differently than its winter counterpart, and might have different causes.
“Summer SAD is more of an agitated depression,” said Rosenthal, a clinical professor of psychiatry at the Georgetown University School of Medicine. While those with winter SAD tend to oversleep and overeat, summer SAD often shows up with insomnia and lowered appetite.
When asked, people with summer seasonal affective disorder usually say that what bothers them most is the heat and humidity. Each person’s pattern may differ — Ashly’s symptoms usually start in May and vanish in October — but the disorder returns regularly. Still, even the researchers who study summer SAD said there are other uncertainties around it.
“What causes summer SAD? We assume it’s heat and humidity,” said Kelly Rohan, a psychology professor at the University of Vermont. Studies suggest that some of the same compounds in the body that help regulate mood, such as norepinephrine, serotonin and dopamine, have also been linked to regulating body temperature. “But what is the trigger that makes people vulnerable?” she said.
A few researchers, using year-round depression data, have questioned the idea that seasonal affective disorder exists at all. In 2016, researchers from Auburn University at Montgomery, in Alabama, reported that major depression was not associated with a seasonal pattern.
Rohan conducted a similar study in 2009 that evaluated surveys of about 2,000 children and adolescents, and found no seasonal pattern to their mood. That doesn’t mean that SAD doesn’t exist, she said, but that, in an ocean of modern depression, it is difficult to pick out the much smaller seasonal currents.
Those who study these seasonal currents are concerned that summer SAD, and mental health challenges in general, will increase with climate change. A 2018 study in the journal Nature Climate Change found that both suicide rates and social media posts using language signaling lower mood increased as average monthly temperatures rose in the U.S. and Mexico. The study suggested that as many as 21,000 additional people in these countries could die by suicide by 2050, based on projected temperature increases of 2.5 degrees Celsius in the U.S. and 2.1 degrees Celsius in Mexico.
Another seasonal challenge that could worsen with climate change — and play into mood — is pollen, said Teodor Postolache, a professor of psychiatry at the University of Maryland School of Medicine. He said the immune response to allergens like pollen might create a cascade of changes in the body, including the release of biological compounds called cytokines that regulate inflammation and have been connected to depression.
Postolache and his colleagues study seasonal mood change in Old Order Amish people in Lancaster County, Pennsylvania, who have limited exposure to electric light, making them more subject to natural variations in day length.
When the researchers surveyed about 1,300 Old Order Amish, they found the small group who felt at their worst in the summer also tended to report that high-pollen days worsened their mood. Previous work with college students also suggested a link between low summer mood and pollen sensitivity.
While more research is needed, Postolache said, “When you feel at your worst relates really well to day length in the winter” and “to the heat and the pollen for the summer difficulties.”
One difficulty in detecting SAD is its transitory nature. Once fall comes, Ashly said, “you forget all about it.” Even without seasonal affective disorder, other stresses can trigger depression during summer, like being untethered from the structure of school.
Tonya Ladipo, a licensed clinical social worker and founder of The Ladipo
Group in Philadelphia, suggested keeping a mood journal to track your moods and look for patterns. This helped Ashly and her therapist recognize her cycle of summer SAD. If a low mood doesn’t improve within about two weeks, Ladipo recommended seeking out a mental health professional.
If heat dampens your mood, Rosenthal said that some of his patients have found that frequent cold showers or baths can help; others experienced some relief by walking early in the morning. Sometimes intense summer light, along with heat and humidity, can be problematic; decreasing exposure with dark glasses or curtains may also be worth trying.
Even if summer’s effect is subtle, it’s worth noticing. “Maybe you can get through your day, but you’re not feeling your best,” Ladipo said. “That still warrants attention.”