LAUSR

Longitudinal analyses investigated (a) the co-occurrence of marijuana use and conventional cigarette smoking within time and (b) bidirectional associations between marijuana and conventional cigarette use in three developmental periods: adolescence, young adulthood, and adulthood. A cross-lag model was used to examine the bidirectional model of marijuana and conventional cigarette smoking frequency from ages 13 to 33 years. The bidirectional model accounted for gender, school-age economic disadvantage, childhood attention problems, and race. Marijuana use and conventional cigarette smoking were associated within time in decreasing magnitude and increased cigarette smoking predicted increased marijuana use during adolescence. A reciprocal relationship was found in the transition from young adulthood to adulthood, such that increased conventional cigarette smoking at age 24 years uniquely predicted increased marijuana use at age 27 years, and increased marijuana use at age 24 years uniquely predicted more frequent conventional cigarette smoking at age 27 years, even after accounting for other factors. The association between marijuana and cigarette smoking was found to developmentally vary in the current study. Results suggest that conventional cigarette smoking prevention efforts in adolescence and young adulthood could potentially lower the public health impact of both conventional cigarette smoking and marijuana use. Findings point to the importance of universal conventional cigarette smoking prevention efforts among adolescents as a way to decrease later marijuana use and suggest that a prevention effort focused on young adults as they transition to adulthood would lower the use of both cigarette and marijuana use.