The Temperamental Determinants of Stressors as Life Changes

Abstract

Behavioral genetic studies have demonstrated the heritability of many variables taken to be measures of environment and previously thought to be determined only by environment. It has been also shown that personal variables may determine the appearance of stressors understood as life changes (events). The hypothesis underlying this study predicted that the genetic factor does not contribute to the variance of subject-independent stressors, whereas in case of subject-dependent stressors the contribution of the genetic factor is essential. Further, it was hypothesized that temperamental traits that moderate the intensity of experienced stressors account for a considerable portion of the genetic variance of subject-dependent stressors. The study was conducted on 245 pairs of MZ and 219 pairs of DZ twins aged from 19 to 66. Stressors were assessed with the Polish adaptation of the Rahe 's Recent Life Changes Questionnaire. Based on two preliminary studies, life events were divided into three following categories: subject-independent life events, negative subject-dependent life events, and challenges. Temperament traits were measured by means of the Formal Characteristics of Behavior-Temperament Inventory. The data, based on structural equation models and multivariate genetic analysis, allowed for the following conclusions: (1) The variance of independent stressors can be explained by environment only, whereas the additive genetic model best fits the subject-dependent stressors. (2) Heritability of negative, subject-dependent stressors is lower than in case of challenges. (3) Temperament variables, among them especially activity, explain only one type of stressors challenges. (4) Additional analysis of data confirm the role of activity as a moderator that increases the risk of environmental effects and evokes challenges.