The Internalizing Scale has very good psychometric properties and can be used, in studies that incorporate the SSAGA interview, to study the association between lifetime internalizing characteristics and problematic alcohol and substance use. The scale is unidimensional and has good internal consistency. Its validity is supported by associations with two other dimensional measures of internalizing characteristics found in the Youth and Adult Achenbach Self Report Internalizing Scales and the Neuroticism-Extraversion-Openness Five-Factor Personality Inventory Neuroticism Scale. Although just moderate, the magnitude of the correlation between the proposed Internalizing Scale and the Achenbach Internalizing Scale was similar to the correlation between the Neuroticism Five-Factor Personality Inventory Subscale and the Achenbach Internalizing Scale. Our scale was more correlated with the Achenbach Internalizing Scale than with the Neuroticism Five-Factor Personality Inventory Subscale, perhaps because the Achenbach Internalizing Scale is an amalgam of disorder-based symptoms, most similar in construction to the SSAGA-based Internalizing Scale. In contrast, the lower strength of the correlation between the SSAGA-based Internalizing Scale and the Neuroticism Scale may reflect the fact that the Neuroticism Scale does not derive from specific disorders
