A study in JAMA found a correlation between ecstasy use and difficulty remembering words.

[The doctors] recruited 188 volunteers (average age 22) who had not used Ecstasy but reported that they were likely to try it soon. Within three years of the initial evaluations, which took place between April 2002 and April 2004, 58 individuals began using Ecstasy. They were compared with 60 individuals who had the same age, sex and intelligence score but who did not use Ecstasy during the follow-up period. All participants took tests that assessed various types of memory—including attention, verbal memory for words and language, and visual memory for images—at the beginning and end of the study. Verbal memory was tested by memorizing a series of 15 words and repeating them immediately and again 20 minutes later.

During the initial round of testing, wrote the doctors, there were no statistically significant differences in test scores between those who went on to use ecstasy and those who didn’t. During the follow-up test, ecstasy users exhibited “significantly lower” verbal recall and verbal recognition abilities.