Childhood Physical Abuse and Sociopathy: Is This Link Magnified among Firstborn Children?

The Psychopathic Deviate scale of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) provides a valid psychometric index of sociopathic tendencies in both clinical and nonclinical samples. Childhood physical abuse has provided a robust predictor of sociopathic penchants. The link between childhood physical abuse and MMPI-2 Psychopathic Deviate scores was examined (N = 322) as a function of birth order. A significant childhood physical abuse by birth order interaction was found (p < .0001, eta(2) = .62) with a 6-fold increase in relative risk of a Psychopathic Deviate elevation (T > 70) found for firstborn participants. Childhood physical abuse predicted Psychopathic Deviate scores for firstborn (r = .50, p < .0001, d = 1.15) and middle-born (r = .24, p = .006, d = .49) offspring. Harris-Lingoes subscale scores suggested firstborns felt selectively alienated from self and others in response to childhood physical abuse experiences.