Depression has long been treated as a brain chemistry disorder, but a new study suggests that the immune system may play a more significant role than previously thought.
A systematic review and meta-analysis has found that anti-inflammatory treatments not only reduce depressive symptoms but also alleviate anhedonia — the inability to feel pleasure — in individuals with both depression and high levels of inflammation.
“This finding could make immunopsychiatry an even more relevant field of study,” said Annelise Madison, co-first author of the study and assistant professor of clinical psychology at the University of Michigan Eisenberg Family Depression Center.
Immunopsychiatry examines the connection between the immune system and mental health.
Published in the American Journal of Psychiatry, the research suggests that targeting inflammation could offer a personalized treatment option for patients who haven’t responded to traditional antidepressants. It also highlights potential new directions for depression therapy, particularly for those with elevated inflammation levels.
The systematic review involved 19 studies, while the meta-analysis included 14. Researchers analyzed 19 clinical trials in which patients with depression and high inflammation were treated with anti-inflammatory drugs or placebos over periods of up to 12 weeks. The treatments showed significant benefits in reducing both depression and loss of pleasure, with no increase in serious side effects.
Despite these promising results, Madison cautioned that the use of anti-inflammatory drugs in psychiatry is currently off-label, as the FDA has not approved them for treating depression.
Madison also pointed out that earlier studies on anti-inflammatory treatments for depression yielded mixed results, likely due to the lack of focus on inflammation when recruiting participants. By considering inflammation levels, future trials may produce more consistent findings.
The study was supported by the National Institute of Mental Health, the L.I.F.E. Foundation Research Grant, Harvard University’s Mind Brain Behavior Initiative, and Massachusetts General Hospital’s Early Career Investigator Award. Additional contributions came from researchers at Harvard and Emory University.
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