In total, 20 studies (24 genome scans, 5428 families) were identified (5–24), and finally 12 studies (15 complete genome scans, 3404 families) met criteria and were included in the GSMA (5–16), as listed in Table 1. Eight studies (9 genome scans, 2024 families) were not included for the following reasons (17–24). Four studies are repeated analyses of the Framingham Heart Study (6, 19–21); from these, the result from Goode (6) was used because the whole-genome linkage result was available from the published graph. Three linkage analyses have been performed on the data of the Collaborative Study on the Genetics of Alcoholism (7, 17–18); we used the result from Bierut (7) since the whole-genome linkage results were available from the authors. Two linkage analyses on two different assessments of smoking behavior (9, 22) were performed for the same sample from the Netherlands Twin Register; the result for “maximum number of cigarettes per day” was included (9). In the earliest study, the authors carried out a 2-stage genome scan, and only the result from stage 1 was used since stage 2 was
