Long-term Ecstasy users risk brain damage, memory loss and an increased chance of developing Alzheimer's disease, new research suggests.

Dutch researchers used MRI scans to study the brains of 10 men in their mid-20s who had taken an average of 281 ecstasy tablets over the previous six and a half years, and seven peers who had taken other drugs.

They found that the hippocampus - the part of the brain controlling memory - was 10.5% smaller among the ecstasy users, and their overall grey matter 4.6% less.

"These data provide preliminary evidence that Ecstasy users may be prone to incurring hippocampal damage", and may help explain the memory loss witnessed among such people in previous studies, the co-authors wrote in the Journal of Neurology, Neurosurgery and Psychiatry.

"Hippocampal atrophy is a hallmark for disease of progressive cognitive impairment in older patients, such as Alzheimer's disease", they added.

Professor David Nutt, the government's former lead adviser on drugs misuse, said, however, that the "interesting pilot study ... is underpowered to provide definitive evidence of an effect of ecstasy". Evidence suggests that many drugs, including alcohol, can damage someone's memory, Nutt added.