Three case pools were constructed: (i) AD subjects with no history of ND despite a history of cigarette experimentation (AD+/ND−; N=625); (ii) ND subjects with no history of AD (AD−/ND+; N=674), but in almost all cases a history of experimentation with alcohol; and (iii) comorbid AD and ND subjects (AD+/ND+; N=599); an AD−/ND− control pool (N=488) was also created (Table 1). Each pool was constructed separately for males and females to allow for the examination of possible sex-specific effects. No more than one individual per family was used in the pooling experiment.
