Additionally, the degree of stability in the relationship between alcohol and tobacco use and cannabis initiation differed in EA vs. AA women. In AA women, alcohol and tobacco use conferred a consistent, significant risk for cannabis initiation across the period of risk, whereas the association between alcohol and tobacco use and cannabis initiation in EA women was unstable. For alcohol, before the age of 15 and after the age of 18 no significant association was revealed for cannabis initiation; however a substantial risk was associated with alcohol use for cannabis initiation between 15 and 18 years old in the EA women. A similar pattern emerged for tobacco use with the highest hazard for cannabis initiation during adolescent years for EA women but a consistent increase in risk in AA women. These findings indicate the risk conferred by use of alcohol and tobacco are specific to early initiation in EAs but in AAs–who initiate alcohol and tobacco later and in which use is slightly less normative–use at any age may contribute to pathological outcomes. This is consistent with previous findings in
