The effects of licit and illicit recreational drugs on prospective memory: a meta-analytic review

Bradley Platt,Valerie H Curran,Peter G Rendell,Ciarán O’Driscoll,Sunjeev K Kamboj

doi:10.1007/s00213-019-05245-9

Bradley Platt, Valerie H Curran + Show 3 more

Open Access

https://doi.org/10.1007/s00213-019-05245-9

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Abstract

RationaleThere are no recent reports summarising the magnitude of prospective memory (PM) impairments in recreational drug users.ObjectiveWe performed a meta-analysis of studies (with a parallel group design) examining PM performance in users of common recreational drugs (including alcohol and tobacco) who were not intoxicated during testing. Studies were also evaluated for the presence of methodological bias.MethodsTwenty-seven studies were included in the meta-analysis following literature searches of MEDLINE, EMBASE and PsycINFO. Effect sizes (standardised mean difference; SMD) were calculated separately for the effects of alcohol, cannabis, ecstasy, methamphetamine and tobacco use. The influences of drug use and study characteristics on effect sizes were explored using meta-regressions. Sources of study bias were also assessed.ResultsHeavy drinkers and regular drug users tended to perform worse than controls on event and time-based PM tasks. Effect sizes (standardised mean differences; SMDs) for event-based PM impairment across the different drug-using groups/heavy drinkers ranged between − 1.10 and − 0.49, with no 95% CI crossing 0.00. SMDs for time-based PM ranged between − 0.98 and − 0.70. Except for the CIs associated with the ES for smokers’ time-based PM performance, no CIs crossed 0.00.ConclusionsAlthough all drug-using groups showed moderate-large impairments in event and time-based PM, effect sizes had low precision and moderate-high levels of heterogeneity. In addition, several methodological and reporting issues were identified in the majority of studies. As such, considerable uncertainty remains regarding the role of confounds and the magnitude of PM impairments in non-intoxicated recreational drug users.

Highlights

The maladaptive use of recreational substances is a major international public health concern
Our analyses revealed that regular users of alcohol, cannabis, ecstasy and opiates performed significantly worse than controls on event- and on time-based prospective memory (PM) tasks
The effect sizes for impairments on event-based PM tasks were moderate–large in smokers and heroin users, small–large for alcohol, ecstasy and methamphetamine use, and negligible–large for cannabis

Summary

Introduction

The maladaptive use of recreational substances is a major international public health concern. According to McDaniel and Einstein’s (2000) multi-process model, PM relies on either spontaneous retrieval (in which the occurrence of a triggering event promotes retrieval of the intended action from long-term memory) or strategic monitoring (in which the participant actively monitors the environment for triggering cues). When cognitive processes involved in on-going behaviour support the processes involved in PM, the tasks are defined as ‘focalcue’ tasks and are thought to rely on spontaneous retrieval. When these do not support the processes involved in PM, the relevant tasks are defined as ‘non-focal’ and depend upon strategic monitoring. Whilst event-based tasks require participants to perform an intention in response to an external cue (e.g. Bbuy a birthday present at the shopping centre^), time-based tasks require participants to perform an intention at a specific time or after a delay (e.g. call the plumber at 2 pm)

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