Analyses controlled for age at intake to rule out ceiling effects for rapid progression in younger respondents (i.e., those entering treatment at a young age might show rapid progression due to less opportunity to engage in slower drinking progression while young) or for rapid progression in older respondents (i.e., those entering treatment at an older age might show rapid progression because age at intake was censored at age 18). Analyses excluded 51 (1.5%) individuals who reported reaching any milestone at a younger age than age of first drink. Abstainers were included in time-to-attainment analyses but (by virtue of not having met any milestones) were excluded from duration analyses and analyses modeling age of onset.
