American soldiers traumatised by fighting in Iraq and Afghanistan are to be offered the drug ecstasy to help free them of flashbacks and recurring nightmares.
The US food and drug administration has given the go-ahead for the soldiers to be included in an experiment to see if MDMA, the active ingredient in ecstasy, can treat post-traumatic stress disorder.
Scientists behind the trial in South Carolina think the feelings of emotional closeness reported by those taking the drug could help the soldiers talk about their experiences to therapists. Several victims of rape and sexual abuse with post-traumatic stress disorder, for whom existing treatments are ineffective, have been given MDMA since the research began last year.
Michael Mithoefer, the psychiatrist leading the trial, said: "It's looking very promising. It's too early to draw any conclusions but in these treatment-resistant people so far the results are encouraging.
"People are able to connect more deeply on an emotional level with the fact they are safe now."
He is about to advertise for war veterans who fought in the last five years to join the study.
According to the US national centre for post-traumatic stress disorder, up to 30% of combat veterans suffer from the condition at some point in their lives.
Known as shell shock during the first world war and combat fatigue in the second, the condition is characterised by intrusive memories, panic attacks and the avoidance of situations which might force sufferers to relive their wartime experiences.
Dr Mithoefer said the MDMA helped people discuss traumatic situations without triggering anxiety.
"It appears to act as a catalyst to help people move through whatever's been blocking their success in therapy."
The existing drug-assisted therapy sessions last up to eight hours, during music is played. The patients swallow a capsule containing a placebo or 125mg of MDMA - about the same or a little more than a typical ecstasy tablet.
Psychologists assess the patients before and after the trial to judge whether the drug has helped.
The study has provoked controversy, because significant doubts remain about the long-term risks of ecstasy.
Animal studies suggest that it lowers levels of the brain chemical serotonin, and some politicians and anti-drug campaigners have argued that research into possible medical benefits of illegal drugs presents a falsely reassuring message.
The South Carolina study marks a resurgence of interest in the use of controlled psychedelic and hallucinogenic drugs. Several studies in the US are planned or are under way to investigate whether MDMA, LSD and psilocybin, the active ingredient in magic mushrooms, can treat conditions ranging from obsessive compulsive disorder to anxiety in terminal cancer patients.