Inflammation as a Cause of Depression: New Drug Shows Results in Treatment-Resistant Cases

Scientists from the University of Bristol and their colleagues tested an immunomodulatory drug in patients with treatment-resistant depression. The phase 2 study included individuals for whom standard therapy had been ineffective.

The results were encouraging. Patients who received the new drug showed a significant reduction in depressive symptoms compared to the placebo group. The drug was particularly effective in participants who initially had elevated levels of systemic inflammation (based on blood markers).

This supports the growing hypothesis that in a substantial proportion of patients with severe depression, chronic inflammation plays a key role by disrupting brain function. In such cases, traditional antidepressants that act on serotonin and other neurotransmitters are often insufficiently effective.

“We have shown that targeting the immune system could become a new therapeutic direction for those who do not benefit from existing medications,” the study authors noted.

This is still a phase 2 study. Larger phase 3 trials are needed to confirm efficacy and safety. Nevertheless, the findings are considered an important step toward personalized treatment of depression — when therapy is selected based on a patient’s biological characteristics, particularly their level of inflammation.

The study was published in the journal Molecular Psychiatry.

Sources: University of Bristol. Anti-inflammatory drug effective for treatment-resistant depression. Molecular Psychiatry, 2026.