There is a lack of test-retest reliability data for the scale. However, Bucholz and colleagues25 demonstrated good one-week test-retest diagnostic reliability for the SSAGA. Since the Internalizing Scale is, like diagnosis, based on aggregations of single SSAGA questions, it is reasonable to expect that its test-retest reliability might also be acceptable. However, further work is needed to support this hypothesis. Another limitation of this study was that it includes data obtained across 12 years, where an accumulation of differences in the administration or coding of the SSAGA (interviewer drift) may have occurred. However, interviewer- and site-specific drift in the Collaborative Studies on the Genetics of Alcoholism have been minimized by intensive interviewer training sessions and monthly conference calls to review coding and problematic subject responses.23 In addition, scales used for assessing convergent validity were available only for 25% to 60% of the participants (see Table 1). However, all results reported in this manuscript were similar when different random samples of all data available were used and also when a sample with complete data for all variables was examined.
