A research team from Johns Hopkins University, Baltimore, USA, found that monkeys who were given Ecstasy - also known as MDMA - for as little as four days suffered brain damage.

Dr Alan Leshner, director of the US National Institute on Drug Abuse, which funded the study, said: "People who take MDMA, even just a few times, are risking long-term, perhaps permanent, problems with learning and memory."

MDMA is a stimulant which produces a state of euphoria and well-being.

It has been linked with at least 60 deaths in Britain since it first became popular in the late 1980s.

The drug affects levels of the brain chemical serotonin which plays an important role in the regulation of mood and emotion.

Squirrel monkeys

The Johns Hopkins team gave either salt water or Ecstasy to some squirrel monkeys twice a day for four days.

Two weeks later they killed half the monkeys and looked at their brains.

They found damage to neurons associated with serotonin.

Writing in the Journal of Neuroscience, they report that the areas that were particularly affected were the neocortex, the outer part of the brain which is associated with conscious thought, and the hippocampus, associated with long-term memory.

Six to seven years later the rest of the monkeys were killed and their brains examined. They had not completely recovered from the damage.

Serotonin neurons had recovered in some parts of the brain, but in other areas there was no evidence of recovery whatsoever.