A reciprocal effects analysis of cannabis use and perceptions of risk

Background and Aims Adolescents and young adults increasingly view cannabis as a relatively safe drug. Perception of risk associated with cannabis use is correlated negatively with the prevalence of use, but the causal nature of this association is debated. The aim of this study is to quantitate the reciprocal associations between cannabis use and risk perception in a longitudinal panel of emerging adults. Design Observational study of longitudinal data from the Monitoring the Future longitudinal study using autoregressive cross-lagged panel analyses to investigate reciprocal associations between cannabis risk perception and frequency of past-year cannabis use. Setting Surveys administered to 12th-grade students from the United States general population. Participants A total of 9929 12th-grade students (mean age 18.0 years) who were surveyed initially during 2000-05 and follow-up data until approximately 23-24 years old (three waves; n=9929). Measurements Perception of risk association with cannabis use and frequency of past-year cannabis use. Results At baseline, 33% of the 12th-graders used cannabis in the past year versus 28% by the third follow-up; 83% believed that smoking cannabis regularly carried moderate or great risk versus 78% by the third follow-up. All cross-lagged paths in both directions were statistically significant (all P<0.001), consistent with reciprocal influences between cannabis use and risk perception. The negative association between past-year cannabis use and subsequent risk perception (standardized coefficient range -0.21 to -0.27) was stronger than that between risk perception and subsequent use (standardized coefficient range -0.08 to -0.11; confidence intervals did not overlap with those for the coefficients reported above). Similar results were obtained when the analysis was limited to those who had never used cannabis prior to baseline. Conclusions Longitudinal associations between cannabis use and perception of risks from cannabis use are reciprocal in nature, with a stronger association between cannabis use and lower subsequent risk perception.