A New Depression Treatment Targets the Immune System, Not the Brain

Depression has long been treated as a disorder of brain chemistry. A trial published on 20 May 2026 in JAMA Psychiatry offers a different angle: for some people, the problem may lie in the immune system. Researchers tested tocilizumab, an anti-inflammatory drug commonly used for rheumatoid arthritis that works by blocking interleukin-6 (IL-6), a molecule that drives inflammation in the body.

The results, though early, were striking. Among participants who received tocilizumab, 54% achieved remission of their depression, compared with 31% in the placebo group. The researchers calculated a “number needed to treat” of 5 — meaning roughly one in five people benefited who would not have otherwise — which compares favorably with the figure of about 7 often cited for standard SSRIs. Participants also reported improvements in anxiety, fatigue and overall quality of life.

“A trial published on 20 May 2026 in JAMA Psychiatry offers a different angle: for some people, the problem may lie in the immune system.”

Importantly, this was a small, carefully controlled study rather than a finished treatment. Just 30 people took part — 14 receiving the drug and 16 receiving placebo — over four weeks, in work led by the University of Bristol, the University of Cambridge and the Cambridgeshire and Peterborough NHS Foundation Trust. Much larger trials will be needed before any such therapy could reach clinics, and it is likely to help only the subset of patients whose depression is linked to inflammation.

“This is one of the first randomized controlled trials to test immunotherapy for depression, the first to test IL-6R as the treatment target,” said Professor Golam Khandaker. Dr Éimear Foley added that the study “moves us closer to more tailored depression care, where treatments are chosen to better fit a person’s biology.” For the many people who do not respond fully to existing antidepressants, that shift toward precision — matching the right treatment to the right patient — is a genuinely hopeful direction.