1964–1991) provided up to six measurements of AAD symptoms. Amongst this group, 1.9% had reported that they had not or rarely drunk alcohol. For 1,588 individuals (18.9%) two measurements on AAD symptoms were analyzed, for 1,175 (14.0%) three, for 778 (9.3%) four, for 344 (4.1%) five and for 24 individuals (0.3%) six measurements. Additional repeated measures at age 14 or younger or age 33 or older were available but not analyzed for 674 of the 8,398 individuals (8.0%). The relative large number of twins with one survey (N = 4,489; 53.5%) was mainly due to the entry from participants of the YNTR in 2009/2010 who were invited to participate in the ANTR research for the first time (N = 2,151; 47.9%).
