Allergy sufferers who say symptoms like sneezing, sniffling, and red, itchy eyes make them miserable may not be exaggerating. Recent studies show an association between seasonal allergies and clinical depression. While researchers can't say that allergies actually cause people to feel depressed, it does appear that allergy sufferers are more vulnerable to depression.
“Most people who have allergies don’t have depression, and most people who are depressed don’t have allergies,” says Paul S. Marshall, PhD, a clinical neurophysiologist in the department of psychiatry at the Hennepin County Medical Center in Minneapolis. “But I think it’s accurate to characterize allergies as a risk factor for depression.”
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Could it be a risk factor for you? Large-scale population studies suggest that allergy sufferers are roughly twice as likely to have depression as people without allergies.
In one such study, adults with allergic rhinitis (hay fever) were twice as likely to have been diagnosed with major depression in the previous 12 months. In another study, kids who had hay fever at age 5 or 6 were twice as likely to experience major depression over the ensuing 17 years.
More recent research also supports the allergy-depression connection.
In a 2002 study, a team of scientists led by Marshall found that people with hay fever experienced more sadness, apathy, lethargy, and fatigue in late summer, when ragweed season peaks. “That’s just the opposite of what we see in people who don’t have allergies,” says Marshall. Usually, people tend to have a more positive mood in summer, he says.
Making Sense of the Allergy-Depression Link
What’s going on? Some experts explain the allergy-depression connection in psychological terms, focusing primarily on the heavy emotional toll of chronic allergy symptoms.
There’s “no evidence that there is a causality between allergic rhinitis and depression,” says Richard F. Lockey, MD, professor of medicine and director of the division of allergy and immunology at the University if South Florida College of Medicine in Tampa. “But if you can’t breathe through your nose, if you have headaches, if you can’t sleep well at night, there’s a good chance you’re going to feel depressed.”
There is clear evidence that allergies can interfere with sleep, and sleep problems have been linked to poor concentration and depression. But there may also be a biological basis to the “allergy blues” that affect so many people with allergies.
“I am much more on the side of a biological connection,” says Teodor T. Postolache, MD, associate professor of psychiatry and director of the mood and anxiety program at the University of Maryland School of Medicine in Baltimore. Postolache led a 2005 study that found that peaks of tree pollen levels correlated with increased levels of suicide in women.
He says allergic rhinitis is known to cause specialized cells in the nose to release cytokines, a kind of inflammatory protein. Animal and human studies alike suggest that cytokines can affect brain function, triggering sadness, malaise, poor concentration, and increased sleepiness.
Sound familiar? “We’ve all experienced this syndrome to some degree,” says Marshall. “What individuals with severe allergies experience when reacting is similar to the general malaise you feel when you have the flu.”