according to the latest research:
FACT: Ecstasy use appears to impair memory
Specifically: immediate & delayed verbal memory (remembering what someone has just told you), delayed visual recall (the ability to remember images), and short term memory (also known as "working memory").
Overall, Ecstasy users find it more difficult to recall and memorize information than non-E users.
These effects have been detected days, weeks, and months afterwards in both light (20 pills in a lifetime), moderate (20-100 pills) and heavy (100+) users.
FACT: The degree of memory impairment is between 20-40% below average
This is still, technically, well within what is classed as "normal" memory performance. It does not seem to affect users' everyday lives.
SUSPECTED: The more Ecstasy you take, the worse the memory impairment.
The more E you take, the worse your memory performance may be - especially short term memory and immediate vocal recall (Gouzoulis-Mayfrank). This has been confirmed by another, less well designed study (Bolla).
However, nobody yet knows exactly what "more" means. It could be lifetime exposure, monthly dose, frequency or duration of use, or amount of E per single occasion.
UNKNOWN: If you stop taking Ecstasy, your memory will get better again
There is conflicting evidence. Some preliminary evidence from one study (Morgan) appears to imply that abstinence from E for six months may normalize memory performance. And another solid study (Semple) found that memory appeared to recover after abstinence from E.
But another study (Wareing) found that very heavy E users (1300 pills lifetime doses) still performed worse than control subjects even after a year of abstinence. Note: 1300 pills is very heavy use, the equivalent of 3-4 pills twice weekly for 4 years.
UNKNOWN: Ecstasy may affect other brain functions
For instance, moderate E users (93 pills in a lifetime) in one well-designed study (Gouzoulis-Mayfrank) showed worse performance in: problem solving, general knowledge, selective attention, and logical thinking. No other studies have tested these areas yet.
FACT: Smoking marijuana as well as taking E makes memory performance even worse
Marijuana use appears to increase the impairment of working memory or play its own role in memory impairment which may interact with MDMA's effects. (Gouzoulis-Mayfrank)
You can read the details on the main studies here.