GPs and their patients were representatively sampled in nine regions from six European countries (Italy, Germany, Hungary, Latvia, Poland and Spain) using complete registers or local GP associations. In some countries, GPs were randomly sampled from registers while in others sampling was stratified according to pre-selected criteria (e.g. urbanity, size of GP practice). 56.4 % of contacted GPs refused study participation. The majority of GPs refused their participation for reasons unrelated to this study’s characteristics, e.g. tight schedules, insufficient space in the PC facility, lack of interest in research activities generally or current participation in other studies. For countries with populations below 40 million inhabitants (Latvia and Hungary) primary care practices were sampled to be nationally representative. In the remaining countries primary care practices were regionally representative (Italy: Friuli-Venezia Giulia and Tuscany region; Germany: Saxony and Berlin state; Poland: Łódź and Podkarpackie province; Spain: Catalonia autonomous community). In Hungary and Spain, all patients with GP assessment were interviewed. In the remaining countries, patients were selected for interview either randomly or based on stratification (oversampling AUDs cases as judged by the
