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Regular users of the popular club drug ecstasy suffer marked short-term memory loss that can interfere with their ability to learn, according to a new study.

There are also indications that, over the long term, the hallucinogen can cause serious memory impairment, researchers report in today's edition of Neurology.

Dr. Konstantine Zakzanis, a psychologist in the division of life sciences at the University of Toronto, said ecstasy affects the hippocampus, the part of the brain associated with learning and the consolidation of new memories.

"For those who use ecstasy repeatedly, there is preliminary evidence to suggest memory processes can be impaired with continued use of the drug," he said.

But he was quick to add that those who experiment with the drug, using it only once or twice, do not appear to suffer any ill effects.

Ecstasy is the street name for the drug methylenedioxymethamphetamine (MDMA). It is popular at raves because it stimulates the central nervous system, allowing users to dance all night. Users say the drug also causes a spiritual high and feelings of relaxation.

Researchers at the U of T and the Centre for Addiction and Mental Health recruited 15 regular ecstasy users for their study. The participants, aged 17 to 31, took the drug, on average 2.4 times a month.

Dr. Zakzanis said the test subjects twice underwent a testing regimen that included measures of intelligence and everyday memory functioning. Over the one-year study period, test scores either declined or remained static. But the main finding was that the retrospective memory of ecstasy users dropped by more than 50 per cent.

Retrospective, or short-term memory, is measured by reading a short passage of prose then having subjects recall the story immediately and again after a brief delay.

Researchers also found that vocabulary and the ability to recall names was affected by ecstasy use, as was the ability to recall a route.

Dr. Zakzanis said that one downside of the research was that it depended on self-reporting of drug use by participants, which is notoriously unreliable. Because ecstasy is a street drug, researchers could not measure the purity of the drug and measure precise intake. (Tablets sold in bars and at raves can contain compounds including MDMA, the related drug MDEA, caffeine, ephedrine and even LSD.)

But, because results were not different among ecstasy users with different drug-use histories, researchers concluded that "memory deficits associated with MDMA do not seem to be an artifact of other drug use."

Ecstasy comes in many forms, the most popular of which is a white tablet that sells for $35 to $40 in Canada. The effects last for about eight hours.

The RCMP, in an internal report obtained by the Canadian Press, said Canada is becoming a safe haven for manufacturers of designer drugs such as ecstasy because there are few laws regulating the chemical ingredients required to make the drugs.