The Internalizing Scale was constructed by drawing questions from several sections of the SSAGA interview that address internalizing characteristics. Since the SSAGA is a long and detailed assessment, several iterations were considered prior to the version of the scale presented in this manuscript. Earlier versions of the Internalizing Scale had up to 32 items with scores of 0 or 1, reflecting diagnostic criteria for the 6 disorders contained within it. However, because these disorders contain differing numbers of criteria, they were unequally represented in the scale (e.g., agoraphobia contributed 2 items, whereas obsessive-compulsive disorder contributed 8). Later iterations balanced the input of each disorder (see below) and added suicidal thoughts and behaviors from the SSAGA. The final version of the Internalizing Scale, reported in this manuscript, provides superior item balance. The current version also exhibits slight improvements in terms of higher internal consistency, larger effect sizes with scales used for validation, and larger effect sizes with demographic and alcohol and other substance characteristics. It also performed slightly better when heritability was measured in a genetic framework (further details about this
