(51). Where such variations in risk were found for parental AUDs and parental separation, interactions with age that correspond to key developmental periods were created and entered into the model (i.e., early childhood [12 and younger], puberty [13–15], early adolescence (16–18), and young adulthood [19 and older]) (52). For example, subjects with 2 AUD-affected parents may have greater cumulative incidence of alcohol initiation before age 16 than later, and that difference in cumulative incidence before and after age 16 is modeled with an age interaction (see Supplemental Figure 1 for visual representation). For control variables, the average association with the outcome across time was used, since violations of the proportional hazards assumption did not affect the interpretation of the association of parental AUDs and parental separation outcomes (53, 54). Standard errors were adjusted for the non-independence of observations within families using the Huber-White robust variance estimator, and analyses were performed using Stata Statistical Software Release 14 (55).
