Psychedelics cut inflammation in sick animals, not healthy ones

Psychedelics reduced proinflammatory signaling molecules by a large margin in rodents with induced inflammation — and did nothing of the sort in healthy animals, according to a meta-analysis published in Brain, Behavior, and Immunity in 2026.

The study, led by Anna Skovgaard Lerche with researchers at the University of California, San Francisco, and the University of Copenhagen, pulled together published research through February 2026. The team screened 9,195 records and kept 61 studies: 24 done on cells in laboratory dishes, 30 on live animals, and seven human studies covering 10 separate trials.

The headline finding is conditional. In rodents where researchers had triggered inflammation, psychedelics drove down proinflammatory cytokines — signaling molecules that promote inflammation. The clearest drops involved IL-1β, IL-6, and TNF-α in the brain and blood. In healthy rodents, the same drugs left those markers untouched.

Why does inflammation matter for psychedelic research?

Most psychedelic research targets the brain. But inflammation can shape brain function and behavior, and prolonged inflammation raises the risk of psychiatric and neurological disorders. Some researchers suspect part of psychedelics' therapeutic benefit comes from calming immune responses rather than from psychology alone.

The review covers classic psychedelics — psilocybin, LSD, DMT, DOI, and ayahuasca — defined by their action on the 5-HT2A receptor, a serotonin receptor and the main target through which these drugs produce their characteristic subjective effects. MDMA and ketamine, which act through other mechanisms, were excluded.

What did each type of study show?

• Cell studies: 19 of 24 in vitro studies reported anti-inflammatory effects. Among studies in which inflammation had been induced, 19 of 21 found such effects.
• Animal studies: 25 of 30 reported anti-inflammatory effects. All 24 animal studies with an inflammatory challenge found reductions. Of the six animal studies without one, five found proinflammatory effects — mostly at very high doses or after repeated dosing over weeks.
• Human studies: results split three ways. Of 10 trials, three found anti-inflammatory effects, three found proinflammatory effects, and four found none. Some proinflammatory results were short-term shifts in immune cells within hours of dosing, similar to those caused by the stimulant dextroamphetamine.

Only one human trial included participants with confirmed elevated inflammation: a study of ayahuasca in people with treatment-resistant depression, which found the brew reduced the inflammatory marker C-reactive protein compared with placebo. Most other human studies enrolled people without elevated inflammation, which may have removed any chance of detecting anti-inflammatory effects.