In this rat study, psilocybin on its own produced antidepressant-like effects that lasted up to nine weeks, but giving lorazepam, a commonly prescribed benzodiazepine, beforehand completely blocked those long-term benefits. Animals that received lorazepam before psilocybin behaved no differently from untreated controls and showed altered expression of brain genes linked to neuroplasticity. While this work is preclinical, it raises a clear caution for psychedelic therapy: benzodiazepines may interfere with the brain changes thought to support psilocybin’s lasting antidepressant effects, an important consideration for patients already taking anti-anxiety medications.