Causal Models of Gray's Behavioral Inhibition System, Depression, and Anxiety Investigated with Twin Methodology

Abstract

Direction of causation between the Gray's Behavioral Inhibition System (BIS), depression, and anxiety was investigated. Data of 424 twin pairs were subjected to direction of causation modeling, which is a method for inferring causal relationship from cross-sectional family data. Four causal models were examined: (1) BIS influences depression/anxiety, (2) depression/anxiety influences BIS, (3) they have mutual causal relationship, and (4) correlations between them are caused by a third variable, such as latent genetic and environmental factors. Results indicated that Model 1, which assumes BIS to have a causal influence, well fitted both depression and anxiety. When influences from BIS were considered, direction of causation modeling revealed that depression and anxiety have positive causal influences on each other. These results support the view that BIS is a diathesis for psychopathology. Results also suggest that interventions aimed at either depression or anxiety may improve the other mood state.