The legality of cannabis and public perceptions of it have shifted in the United States. However, scientific debates about the physical and mental health consequences of cannabis are unresolved.
‘No long-term cognitive effects are seen in adolescents and young adults, as the impact of cannabis use diminishes after 72 hours.’
Nearly 69 studies published between 1973 and 2017 including 2,152 cannabis users and 6,575 individuals with minimal cannabis use for comparison. The results from cognitive tests administered in studies have been measured.
This was a systematic review and meta-analysis. A meta-analysis combines the results of multiple studies identified in a systematic review and quantitatively summarizes the overall association between the same exposure and outcomes across all studies.
The authors of this study were J. Cobb Scott, Ph.D., of the University of Pennsylvania Hospital, Philadelphia, and coauthors.
Small cognitive effects were associated with heavy/frequent cannabis use among adolescents and young adults and the results suggest they faded substantially with abstinence longer than 72 hours.
Consideration of other relevant factors is needed when interpreting the results, including that use of all psychoactive substances is associated with risk, that functional outcomes may be more important than measures of cognitive function, and the study cannot make causal conclusions about marijuana and cognitive functioning.