Observational studies suggest that heavy, habitual marijuana use in adolescence may be associated with cognitive decline and adverse educational outcomes. However, conflicting data exists. The authors of this study used data from a large population-based prospective cohort of 1155 individuals from the United Kingdom to investigate the effects of cannabis use by age 15 on subsequent educational outcomes. They also explored the relationship between tobacco use and educational outcomes to assess for possible bias. The primary educational outcomes were performance in standardized English and mathematics assessments at age 16, completion of 5 or more assessments at a grade level C or higher, and leaving school having achieved no qualifications. Exposure was measured by self-report and serum cotinine levels.
* In fully adjusted models both cannabis and tobacco use were associated with adverse educational outcomes.
* A dose response effect was seen with higher frequency of cannabis use associated with worse outcomes.
* Adjustment for other substance use and conduct disorder attenuated these effects and tobacco had a stronger association than cannabis.
This data sheds more light on a possible association between early exposure to cannabis and tobacco and subsequent poor educational outcomes. However, given the nature of the analysis, causality cannot be implied. Further research is needed at longer follow-up periods to gain more understanding of the relationship between cannabis use in adolescence and educational outcomes. Jeanette M. Tetrault, MD
Source: Addiction. 2015;110(4):658–668.