Illegal drug use is proposed to interfere with the neurobiological functioning of the brain by damaging the neurotransmitters communication systems that are believed to be responsible for cognitive abilities, including perception, attention, and memory. This review specifically examined effects of illegal drug use on prospective memory (PM). Twenty-five studies were included in this review which were divided into two broad categories based on used testing methods: studies with self-report testing methods and studies with lab-based testing methods.
The quality of included studies was assessed in five categories: sample type, sample size, abstinence period, testing methods and control for confounding factors. The overall quality of evidence was moderate for twenty-two studies and low for three studies. The results from the studies employing self-report were inconsistent as illegal drug users exhibited PM deficits in some studies, but not in others. However, the studies with lab-based testing methods demonstrated more consistent findings with illegal drug users scoring worse than non-users on the various types of the psychological test battery, including the MIST, JAAM and CAMPROMPT. There were also mixed findings on the link between the dosage of drug taken and level of PM deficit. Most studies controlled various potential confounds (education level, IQ, sleep quality etc.), therefore, it is unlikely that these findings were due to individual differences. Overall, the review suggests that PM deficits were associated with a various type of illegal drug use.
Dr Eddy J Davelaar Birkbeck University