This study uses behavior genetic (BG) methodology to investigate Freud's theory of depression as aggression directed toward the self (1930) and the extent to which genetically and environmentally influenced aggressive tendencies contribute to depressive symptoms. Data from the Twin and Offspring Study in Sweden (TOSS) is used to demonstrate how, in estimating shared and unique environmental influences, BG methods can inform psychoanalytic theory and practice, particularly because of their shared emphasis on the importance of individual experience in development. The TOSS sample consists of 909 pairs of adult twins, their partners, and one adolescent child per couple. The Center for Epidemiologic Studies Depression Scale (Radloff 1977) was used to measure depressive symptoms and the Karolinska Scales of Personality (Schalling and Edman 1993) to measure internally directed aggression. Genetic analyses indicated that for both men and women, their unique experiences as well as genetic factors contributed equally to the association between internally directed aggression and depressive symptoms. These findings support Freud's theory that constitutionally based differences in aggression, along with individual experiences, contribute to a person's depressive symptoms. Establishing that an individual's unique, not shared, experiences and perceptions contribute to depressive symptoms and internally directed aggression reinforces the use of patient-specific treatment approaches implemented in psychoanalytic psychotherapy or psychoanalysis.Freud's theory of depression as aggression directed inward (1930), while considered by many to be a basic tenet of psychoanalytic theory, lacks strong empirical validation. The absence of such validation is due, in part, to the psychoanalytic tradition of assessing

The current study used factor analysis to assess the degree to which personality characteristics derived from different theories signify the same latent personality constructs, and biometric modeling to understand the genetic and environmental structure of these constructs. Participants were drawn from the Twin and Offspring Study in Sweden (TOSS), and included 318 male twin pairs (129 Monozygotic, 189 Dizygotic) and 544 female twin pairs (258 Monozygotic, 286 Dizygotic). Personality characteristics were assessed via two self-report measures: the Temperament and Character Inventory and the Karolinksa Scales of Personality. Factor analyses identified three personality factors for male and female twins: anxiety, aggression, and sociability. In addition, selfregulation tendencies were integrated within each factor. Biometric analyses indicated that these latent factors were heritable (h 2 ranged from .52 to .67). Most personality characteristics that contributed to each latent factor also demonstrated unique genetic influences. Collectively, these findings underscore the complex nature of aggressiveness, anxiousness, and sociability, and indicate that scales that are conceptually similar may assess genetically distinct systems.

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