A Meta-Analysis of the Relationship Between Abstinence and Neuropsychological Functioning in Methamphetamine Use Disorder

Background: The potential influence of methamphetamine use on neuropsychological functioning is unclear. The aim of this this meta-analysis was to investigate the relationship between abstinence and neuropsychological functioning in people with methamphetamine use disorder. Method: The systematic review protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO: CRD42018083598). Studies were eligible if they (a) included a group that identified methamphetamine as their primary substance of use, (b) comprised participants who reported a period of abstinence from methamphetamine, (c) included healthy comparison participants, (d) included outcome measures that constituted valid and reliable cognitive tests and, (e) were published in English. The search yielded effect sizes based on 1008 abstinent methamphetamine participants and 984 healthy comparison participants. Results: Findings revealed small-to-moderate effect sizes, indicating that methamphetamine participants performed somewhat below controls on learning efficiency, visual-spatial processing, comprehension knowledge, retrieval fluency, processing speed, and psychomotor speed. Three exceptions. in which performance demonstrated no group effect, were in domains of fluid reasoning, short-term working memory, and reaction and decision speed. Discussion: The current results support the hypothesis that methamphetamine use is associated with small-to-moderate cognitive sequelae that persist beyond a period of abstinence. However, we cannot determine whether methamphetamine use leads to long-term neuropsychological impairment via structural or functional brain changes, or whether preexisting deficits in neuropsychological performance and cortical integrity are vulnerability factors for methamphetamine use, or both. Taken together, the results suggest that strong statements regarding impaired cognitive functioning in abstinent methamphetamine users are premature.