Illegal drug use and prospective memory: A systematic review.

•Twenty-seven studies spanning 14 years were reviewed.•Most studies provided moderate quality evidence.•The results from the studies employing self-report were inconsistent.•The studies with lab-based testing methods demonstrated more consistent findings.•Drug users were more likely to score worse than non-users on various PM tests.•There was a link between the dosage of drug taken and level of PM deficit.