Treatment usually includes drugs and antidepressants such as Zoloft, sometimes combined with psychotherapy. "There is a lot of evidence supporting exposure-based therapy", says Dr Brady, "which means re-living the events in a safe setting so patients can separate the inappropriate effect from the trauma." Yet in at least a quarter of cases chronic PTSD is resistant to all treatment.

Gail Westerfield, a writer who lives in South Carolina, was sexually abused by a neighbour when she was a child, and later raped by an acquaintance when a university student. She suffered a range of symptoms including memory problems, bouts of depression, crying fits and tremors.

She was diagnosed with PTSD a decade ago when she was in her 30s. But she found this knowledge cold comfort. "I was probably on half a dozen different kinds of antidepressants over the years", she says, "and they never worked for me. I've had this my whole life, pretty much."

So the results of a clinical trial recently announced by Michael Mithoefer, a psychiatrist in Charleston, South Carolina, are encouraging. Twenty patients with PTSD who had resisted standard treatments-including both Ms Westerfield and the security contractor-were given an experimental drug in combination with psychotherapy. After just two sessions all of them reported dramatic improvement. The compound, methylenedioxymethamphetamine, or MDMA, is not new. Known as Ecstasy, it is illegal nearly everywhere.

Dr Mithoefer's study is part of a broader resumption of research into the therapeutic uses of psychoactive compounds. Scientists in North America, Europe and Israel are studying the use of MDMA, LSD, hallucinogenic mushrooms, marijuana and other banned psychoactive substances in treating conditions such as anxiety, cluster headaches, addiction and obsessive-compulsive disorder. They are supported by private funds from a handful of organisations: the Beckley Foundation in Britain; the Heffter Research Institute and the Multidisciplinary Association for Psychedelic Studies (MAPS) in America.

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