The study relied on self-report data and retrospective assessments of ages of milestone attainment. Although self-reported drinking has been shown to be reliable and valid among youth [47], there is recall bias in estimation of dates of particular events [48,49]. However, compared to age-of-onset research using population-based adult samples [7–9], which relies on retrospection over several decades, this sample may have less biased retrospective age-of-onset dating. In addition, participants are reflecting upon relatively nuanced drinking behaviors. However, differential retrospection biases that may be responsible for differences in progression would presumably be constant across milestone.
