Ecstasy users have more trouble with difficult memory tasks than non-drug takers and even cannabis users, according to new Australian research.
The study provides further evidence that the 'party drug' causes brain damage in regions relating to memory and suggests it also affects learning.
Australian National University psychologists Dr John Brown, Dr Elinor McKone and Dr Jeff Ward wanted to determine why some studies had found an association between ecstasy use and memory deficits, but others had not.
Their study, which appears in the online ahead of print issue of Psychopharmacology, found the key was task complexity - ecstasy users performed worse than other groups as tasks became harder.
Researchers studied three groups of people aged in their early 20s from the general population in 2002, 2003 and 2004-05. Fifty-nine were ecstasy users, 65 non-drug users and 32 cannabis users. Some participants overlapped in the different years.
The participants were asked to complete a number of verbal tasks, ranging from easy to difficult in cognitive complexity. When recalling words from simple tests, memory deficits were similar across the groups, regardless of whether lifetime ecstasy use was rated as low (23 tablets) or high (384).
But as the tasks became harder, ecstasy users performed worse.
Worse than cannabis
McKone, says the simple tasks might compare with your boss asking you to remember one thing, while the hardest task is similar to being in a meeting discussing complex issues.
"When significant differences were found between ecstasy and non-drug users, both groups were compared with cannabis users, as cannabis is associated with short-term memory loss," she says.
"In the hardest task - recalling groups of three unrelated words - ecstasy and cannabis users did very poorly compared with non-drug users.
"When users were given five chances to learn and remember the sets, cannabis users eventually improved and caught up to non-drug users, but ecstasy users never caught up, meaning they can't learn as well as others."
The tests also found ecstasy users failed to implement memory strategies for performing well in the tasks.
During an intermediate test of repeating 16 words in four categories, they were worse than non-drug and cannabis users at recognising and using the categories to help in recalling words.
"Our results support the hypothesis that behavioural deficits of memory in human ecstasy users are more marked on tasks that are more cognitively complex and which heavily load many brain areas including the frontal lobes," the researchers write.
"This could arise because such tasks require a greater contribution from the frontal lobes or greater interaction between multiple brain regions."
Previous neuroimaging studies suggest ecstasy causes lasting brain damage, with regions such as the hippocampus, frontal lobes and sensory areas damaged; all critical to the encoding and retrieval of memories.
Researchers say methylenedioxymethamphetamine (MDMA) - the main psychoactive ingredient of ecstasy - also causes lasting changes to levels of serotonin, a neurochemical which transmits messages in the brain.
"The message is ecstasy is a lot more damaging than people assume it is," says McKone. "When John [Brown] started the study five years ago, drug users knew cannabis was bad for you and that it could set off schizophrenia, but tended to think ecstasy was fun and made you happy and feel great. That isn't the case.
"It definitely damages your memory, particularly when dealing with challenging areas, and is likely to affect you in the workplace. It also damages people socially because it changes the serotonin system, which makes you feel good in the first place."