The tests, devised by Welsh researchers, suggest a "statistically significant" 25 per cent reduction in performance. Other tests devised by the University of Wales in Swansea show that ecstasy users show more impulsivity - a "classic phenomenon" of damage to the frontal lobes of the brain.
The test results were disclosed by Frontline Scotland, a BBC Scotland documentary on ecstasy, which also cited new research in Edinburgh and the United States. These two studies, it claimed, give added weight to previous evidence of long-term damage by the drug.
The new studies suggest that ecstasy may deplete lifetime reserves of the brain chemical serotonin - and this could bring a greater risk in middle age of conditions normally seen only in the elderly, such as Alzheimer's disease.
The Edinburgh research checked the accuracy of these findings by taking a lock of hair from the Scottish volunteers, to check the accuracy of each one's drug history. Brain scans from young ecstasy users were then compared with scans of users of other drugs, and with those of people who never used drugs at all.
Part of the Welsh research involved getting volunteers to listen to a five-sentence news story, then write down as much as they could remember - immediately, and then again after doing other tasks for about 20 minutes.
Ecstasy users could recall only six ideas from the story, while other volunteers could recall about eight.