Social network heavy drinking was assessed by the Important People and Activities Inventory[29] measure in all three studies. A measure of alcohol dependence severity and a measure of negative mood symptoms were derived using integrative data analysis[30]. Twenty items assessing alcohol dependence severity (Supplementary Table 1) were obtained via the Alcohol Dependence Scale[15] in MATCH and COMBINE, the Diagnostic and Statistical Manual for Mental Disorders (DSM) in MATCH (DSM-III-R[32]) and COMBINE (DSM-IV[33]), and the Leeds Dependence Questionnaire[34] in UKATT. Six items assessing negative mood symptoms (Supplementary Table 1) were obtained via the Beck Depression Inventory[35] in MATCH, the Brief Symptom Inventory[36] in COMBINE, and the General Health Questionnaire[37] in UKATT.
