ORIGINS OF INDIVIDUAL-DIFFERENCES IN ANXIETY PRONENESS - A TWIN ADOPTION STUDY OF THE ANXIETY-RELATED SCALES FROM THE KAROLINSKA SCALES OF PERSONALITY (KSP)/

The genetic and environmental origins of individual differences in sco res on the anxiety-proneness scales from the Karolinska Scales of Pers onality were explored using a twin/adoption study design in a sample c onsisting of 15 monozygotic twin pairs reared apart, and 26 monozygoti c and 29 dizygotic twin pairs reared together. The results showed that genetic factors accounted for individual differences in scores on the psychasthenia and somatic anxiety scales. The genetic determinants we re not specific to each scale, but were common to both scales. Shared- rearing environmental determinants were important for individual diffe rences in lack of assertiveness and psychic anxiety, and were common t o both scales. Individual differences in muscular tension were found t o be attributable to the effects of correlated environments. The most important factor explaining individual differences for all scales was the non-shared environment component. The evidence for an aetiological ly heterogeneous anxiety-proneness construct emphasizes the appropriat eness of a multidimensional approach to anxiety proneness.