Early in his career, Teodor Postolache, a psychiatry professor at the University of Maryland, was struck by a peculiar trend that comes up again and again in suicide research. Across decades and in various countries, suicide is much more common in the spring and early summer than other times of year.
Now, Postolache and other researchers believe they have found a curious link between the season and self-harm: pollen-induced allergies.
In 2005, Postolache and his collaborators found that the suicide rate among young women doubled during peak pollen season, and the rate among older women went up by more than four-fold. Last year, researchers in Texas similarly found that suicide attempts in women rose with daily tree pollen counts in the Dallas area. And just last month, a paper published in Environmental Research found that increased pollen in the air raised the risk of suicide in women in Tokyo—meaning this dark trend might apply across cultures.
“I think it points toward a strong link between allergic rhinitis and mental health,” said Christopher Lowry, a professor of integrative physiology at the University of Denver.
Many allergy sufferers might, when their mucous membranes are burning and their sinuses feel like they’re clogged with Silly Putty, say they want to die. And indeed, some of Postolache’s studies have found links between increases in allergy symptoms, aggression, and mood disturbances. But the connection doesn’t seem to be driven by allergy-induced misery alone. Instead, it appears to be caused by an inflammatory chain reaction that allergens set off in the body.
There are several ways in which a severe reaction to airborne allergens might tip the scales for someone at risk for suicide, but here’s one. When a speck of pollen from the air comes into contact with immune cells in the nose, the cells release cytokines—molecules that cells use to communicate messages to one another. Postolache and others believe cytokines might drift through…