The distinctions between alcohol vs. cigarettes and cannabis may be explained in part by the fact that some alcohol use is nearly universal, but the use of cannabis and, increasingly, cigarette smoking, at any age is somewhat deviant. Ninety-three percent of our sample reported using alcohol, compared with 75% for cigarettes and only 47% for cannabis. With such a large proportion of individuals using alcohol, there would be little variance to account for if the outcome of interest were ever vs. never using alcohol. By splitting the risk period, we were in essence predicting age at first drink. Given that alcohol consumption before age 10 is so rare, it was not surprising that CSA-associated risk was concentrated in this young age range, before peer influences on drinking have emerged. As for why the association between CSA and early use was so much stronger for alcohol than for cigarettes or cannabis, this may be a reflection of easier access to alcohol vs. cannabis and/or greater perceived effectiveness of alcohol vs. cigarettes for dampening negative affect associated with experiencing CSA, but these hypotheses have yet to be tested.
