Some limitations are noteworthy. First, our results may not extrapolate to other demographics. Our study did include a population-representative group of African-American women and they did not differ from their European-American counterparts in rates of rVUS or adolescent cannabis use; however they were more likely to report rVUS prior to cannabis onset (Table S1). Also, according to national surveys, Missouri is one of the states with higher rates of unprotected sex reported by youth (1) – findings in other states may differ. Second, legislation related to the Patient Protection and Affordable Care Act (healthcare.gov) may have modified women’s access to contraceptive alternatives, thus, optimistically reducing the prevalence of rVUS in current cohorts. Third, we did not collect data on partner characteristics or direct consequences of rVUS. Alcohol and drug use were considerably more frequently reported as reasons for condom non-use in those who also reported rVUS as well as in early-onset compared with never/late-onset cannabis users (Table S6); however, we are unaware of the extent to which they contributed to rVUS. Finally, reporting bias in age at initiation of cannabis
