Doctors say people with major depressive disorder can see fast, lasting improvement after just one dose of the psychedelic drug dimethyltryptamine (DMT) combined with psychotherapy. A small trial with 34 patients showed a sharp drop in depression symptoms lasting months after the drug wore off. "There is an immediate antidepressant effect that is significantly sustained over a three-month period and that’s exciting because this is one session with a drug, embedded in psychological support," said Dr David Erritzoe, lead investigator at Imperial College London. The trial focused on patients with treatment-resistant depression who do not respond to usual antidepressants. Half received a 21.5 mg dose of DMT intravenously, the other half a placebo. All had psychotherapy and follow-ups. The DMT group improved more, with effects lasting three to six months. DMT is known from ayahuasca, a traditional brew causing intense hallucinogenic trips. The study’s second phase gave all patients DMT but saw no extra benefit from a second dose, suggesting one dose may be enough. The trial was run by Cybin UK, a neuropsychiatric company. This adds to promising results seen with psilocybin, a magic mushroom compound. Dr Erritzoe compared the effect to shaking up snow on a mountain, which smooths the landscape and makes it easier to find new paths in thinking. DMT’s trips last about 25 minutes, shorter than psilocybin’s few hours, possibly making therapy easier to deliver but more intense. If approved, experts expect psychedelic therapies will be offered mainly in private clinics, amid concerns about safety and ethics. Dr James Rucker from King’s College London said, "Quite how these drugs will fit in this world of financial austerity, stigma and opprobrium towards anything that has the word psychoactive in it, I don’t know. It’s interesting to be a part of, but I can’t call it."