Neuropsychological consequences of chronic opioid use: a quantitative review and meta-analysis

Introduction: It is widely assumed within the accumulated literature that neuropsychological function is commonly impaired as a consequence of chronic opioid use. Method: Quantitative and systematic review of the literature on the neuropsychology of chronic opioid use using the meta-analysis of observational studies in epidemiology (MOOSE) and the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines. Results: This meta-analysis suggests that chronic opioid exposure is associated with deficits across a range of different neuropsychological domains. However, the only domains where meta-analysis suggests robust impairment were those of verbal working memory, cognitive impulsivity (risk taking) and cognitive flexibility (verbal fluency). The magnitude of effect across these cognitive domains was medium according to Cohen's benchmark criteria. Discussion: This analysis highlighted methodological problems present in the literature used and the value of utilising meta-analytic techniques to help further elucidate the neuropsychological consequences of chronic opioid use from 'core' addiction phenotypes.