Genetic variation and covariation in the original and restructured clinical scales of the MMPI

The authors investigated genetic variation and covariation among the original Minnesota Multiphasic Personality Inventory clinical and validity scales and the restructured clinical scales. Variation in most of these scales was best explained by a combination of moderate genetic influences and environmental influences not shared by cotwins. Genetic correlations among the standard clinical scales were generally substantial and positive (M = .48), whereas genetic correlations between the clinical scales and the K scale were strong and negative. The restructured clinical scales were strongly correlated with the general Demoralization scale (M = .55), with lower genetic correlations among the remaining scales (M = .39).