The ecstasy drug MDMA could help people recover from post-traumatic stress disorder, a pilot study has found.
Scientists in California combined MDMA treatment in varying doses with psychotherapy on a study of 22 military veterans, three firefighters and a police officer, all diagnosed with PTSD.
Participants were given doses of either 30mg, 75mg or 125mg of MDMA, and on average people in the higher dose groups experienced a greater decrease in PTSD symptom severity than those in the low-dose group.
After two sessions, 86% of participants in the 75mg group, 58% in the 125mg group and 29% in the 30mg group no longer met the diagnostic criteria for PTSD.
A year after the study had ended, 16 of the 26 participants were no longer classified as suffering with PTSD, while two had renewed diagnosis.
Lead researcher Dr Allison Feduccia, from the Multidisciplinary Association for Psychedelic Studies in Santa Cruz, California, said: "Our study suggests that MDMA might help augment the psychotherapeutic experiences and may have a role to play in the future treatment of PTSD.
"However, we would certainly not recommend that individuals try these drugs for the treatment of psychiatric disorders without the support from trained psychotherapists."
MDMA is the main active constituent of ecstasy, a recreational drug which induces feelings of euphoria. Both are class A drugs, and possession can result in up to seven years in prison in the UK.
It was administered to patients during eight-hour long specially adapted psychotherapy sessions, followed by an overnight stay in a clinic, seven days of telephone contact and another three 90-minute sessions.
Researchers said side effects included anxiety, headache, fatigue, muscle tension and insomnia.
There were also temporary increases in suicidal thoughts, and one participant with a history of suicide attempts had to be admitted to hospital before completing the study.
Throughout the trial, neither the participants nor the clinicians knew how the doses of MDMA were being distributed.
Later participants were offered additional MDMA treatment and psychotherapy, and knew what they were receiving.
Commenting in The Lancet Psychiatry journal, professors Andrea Cipriani and Philip Cowen, from Oxford University, said recreational use of the drug raises safety concerns, including fatal toxicity and brain damage.
They added: "With rigorous sourcing of MDMA and close medical and psychological supervision, its short-term use in carefully selected patients with PTSD seems safe."
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Dr Michael Bloomfield, clinical lecturer in general psychiatry at University College London, said the condition could be "devastating" but warned: "Survivors of trauma who are experiencing PTSD should not try this on themselves because of the risks associated with street ecstasy and the need for good quality psychiatric care including psychotherapy in recovering from PTSD."
He also said more research into the uses of MDMA for PTSD was needed.