Although probability of each stage of alcohol and drug use increased with age, rates were almost always lowest for black and other racial/ethnic groups compared with white or Hispanic adolescents. These findings may contradict common assumptions but are consistent with previous investigations in adult and adolescent samples.10,11 No salient sex differences were observed in lifetime alcohol use, whereas minor differences were observed for all other stages of alcohol or drug use among adolescents aged 13 to 16 years. However, for those 17 to 18 years of age, male adolescents had notably higher rates for most stages of alcohol or drug use. These findings are globally consistent with previous reports of the associations between sociodemographic characteristics and substance use and substance use disorders11,12,14,16–21,29 and indicate that sex differences in substance use behavior are most visible after 15 years of age. In conditional analyses, male alcohol users were significantly more likely to transition to regular alcohol use, whereas no sex differences were associated with drug use transitions. Reduced risk for black adolescents was significant only in transitions from alcohol use to regular
