A study involving 42 students who were ecstasy/polydrug users has found that ecstasy, or the regular use of several drugs, affects users' prospective memory (remembering things you plan to do), even when tests are controlled for cannabis, tobacco or alcohol use. Cocaine use in particular was prominently associated with prospective memory impairment. Deficits were evident in both lab-based and self-reported measurements.
Reference:
[164]
(2010). Everyday and prospective memory deficits in ecstasy/polydrug users.
J Psychopharmacol. 0269881109359101 - 0269881109359101.
Full text is available for a limited time at http://jop.sagepub.com/cgi/rapidpdf/0269881109359101v1