Racial/ethnic differences in use of alcohol, tobacco, and marijuana: is there a cross-over from adolescence to adulthood?

Black adolescents in the US are less likely to use alcohol, marijuana, and tobacco compared with non-Hispanic Whites, but little is known about the consistency of these racial/ethnic differences in substance use across the lifecourse. Understanding lifecourse patterning of substance use is critical to inform prevention and intervention efforts. Data were drawn from four waves of the National Longitudinal Study of Adolescent Health (Add Health; Wave 1 (mean age = 16): N = 14,101; Wave 4 (mean age = 29): N = 11,365). Outcomes included alcohol (including at-risk drinking, defined as 5+/4+ drinks per drinking occasion or 14+/7+ drinks per week on average for men and women, respectively), cigarette, and marijuana use in 30-day/past-year. Random effects models stratified by gender tested differences-in-differences for wave by race interactions, controlling for age, parents' highest education/income, public assistance, and urbanicity. Results indicate that for alcohol, Whites were more likely to use alcohol and engage in at-risk alcohol use at all waves. By mean age 29.9, for example, White men were 2.1 times as likely to engage in at-risk alcohol use (95% C.I. 1.48-2.94). For cigarettes, Whites were more likely to use cigarettes and smoked more at Waves 1 through 3; there were no differences by Wave 4 for men and a diminished difference for women, and difference-in-difference models indicated evidence of convergence. For marijuana, there were no racial/ethnic differences in use for men at any wave. For women, by Wave 4 there was convergence in marijuana use and a cross-over in frequency of use among users, with Black women using more than White women. In summary, no convergence or cross-over for racial/ethnic differences through early adulthood in alcohol use; convergence for cigarette as well as marijuana use. Lifecourse patterns of health disparities secondary to heavy substance use by race and ethnicity may be, at least in part, due to age-related variation in cigarette and marijuana use.