"In summary, our data suggest that ecstasy use over a period of months or a few years may cause long term impairment of cognitive performance even when ecstasy is taken in typical recreational and not necessarily very high doses."
Source
E. Gouzoulis-Mayfrank; J. Daumann; F. Tuchtenhagen; S. Pelz; S. Becker;H.J. Kunert; B. Fimm; H. Sass; "Impaired cognitive performance in drug free users of recreational ecstasy (MDMA)," Journal of Neurology, Neurosurgery, & Psychiatry, (June 2000) Vol. 68, p. 724.
http://jnnp.bmj.com/content/6…
