Depression May Be Caused By 'Allergy' to Stress

An over-excited immune system may explain why some people are susceptible to depression, according to new research on mice.

Mice whose immune systems responded to stress by overproducing an inflammatory compound called Interleukin-6 were more likely to become the mousy versions of depressed than mice with non-overactive immune systems, the research found. This same compound is elevated in depressed humans, said study researcher Georgia Hodes, suggesting hope for new depression treatments.

"There's probably a subset of people with depression who have this over-sensitive inflammatory response to stress and that this is leading to the symptoms of depression," Hodes, a postdoctoral researcher at the Mount Sinai Medical Center in New York, told LiveScience.

Hodes added that stress could be thought of as an allergen, like pet dander, with the over-reactive immune system making you depressed rather than giving you runny nose.