In the Add Health study, a parent, preferably the resident mother of each adolescent respondent interviewed in Wave I, completed an interviewer-assisted questionnaire (Resnick et al., 1997). Maternal reports of her substance use were assessed using two questions. Smoking behaviour was assessed as ‘Do you smoke?’ which had two response options, 0 ‘No’ and 1 ‘Yes’. Frequency of alcohol use was assessed as ‘How often do you drink alcohol?’ The six response options ranged from 1 ‘Never’ to 6 ‘Nearly every day’.
