The main outcome measures for the present study were binary variables reflecting whether the respondent met DSM-IV criteria for alcohol, marijuana, or other illegal substance abuse or dependence within the previous 12 months. A diagnosis of DSM-IV alcohol or drug abuse requires that a person meet at least one of four abuse criteria, and a diagnosis of alcohol or drug dependence requires that a person meet at least three of seven dependence criteria. Supplementary table 1 gives examples of the NESARC items related to past-year alcohol dependence; the NLAES items, and items related to other substance use disorders, are similar. The aggregated category of ‘substance use disorders’ included abuse of or dependence on alcohol, marijuana, stimulants, cocaine, opiates, heroin, sedatives, benzodiazepines, solvents, hallucinogens, or other illegal drugs. We also investigated the effects of MLDA exposure on self-reported age of onset of ‘regular’ drinking, based on NLAES and NESARC respondent answers to the question “about how old were you when you first started drinking, not counting small tastes or sips of alcohol?” (NIAAA 2006, page 7).
