Problem alcohol use was defined as the endorsement in any wave of data collection of at least one DSM-IV alcohol abuse symptom or one AD symptom other than tolerance. Respondents with tolerance only, which comprised 30% of cases reporting one or more AUD symptoms, were recoded as non-problem users to create a more conservative definition of problem alcohol use (in keeping with evidence of inflated rates of tolerance endorsement in young drinkers suggestive of misinterpretation of tolerance questions [Caetano and Babor, 2006; Chung and Martin, 2005]).