This study has a number of limitations that must be considered in interpreting its findings. First, the reliability of self-reported age at first drink may have been poorer for older respondents, leading to telescoping, i.e., recall of age at first drink at older/more recent ages. This possibility would be consistent with the older mean age of respondents who started drinking at ages 18 and older, although the possibility of a genuine cohort effect cannot be ruled out. Given that the incidence of AUD decreased with age, any such telescoping might have upwardly biased the positive association of early AFD and AUD incidence. In addition, the validity of the sensitivity analysis may have been somewhat compromised by our inability to ascertain the timing of AFD relative to the onsets of the events and PD used as exclusionary criteria for the low-risk population. Another limitation is the absence of data that would permit testing for mediating effects of low initial level of response to ethanol (Schuckit et al., 1997) and social modeling of drinking behavior. Finally, our family history measures, though highly
