The context specificity of anxiety responses induced by chronic psychosocial stress in rats: a shift from anxiety to social phobia?

The aim of the present study was to evaluate whether the anxiety-increasing effects of chronic psychosocial stress generalize to non-social (i.e. heterotypic) stressful situations. To investigate this issue, we repeatedly exposed rats to predictable or unpredictable psychosocial stress for 5 or 12 days and examined their anxiety in two markedly different contexts: the elevated plus maze and social interaction tests. Psychosocial stress and the social interaction test were administered under highly similar conditions, i.e. the two situations were homotypic. Psychosocial stress did not affect anxiety in the elevated plus-maze under any condition, but markedly increased anxiety in the social interaction test. In contrast, repeated restraint-a non-social stressor heterotypic to both the elevated plus maze and social interaction tests-increased plus-maze anxiety, demonstrating that anxiety in this test was sensitive to repeated restraint, and the effects were manifested in heterotypic situations. Thus, the anxiety-related effects of chronic psychosocial stress-unlike those of the chronic non-social stressor-were context-dependent. This is reminiscent of phobic anxiety, which manifests in specific situations only. In addition, behavior in the social interaction test showed changes that went beyond simple anxiogenesis. Socially stressed rats spent nearly 40% of total time in aggressive interactions. Based on recent data showing that social phobics are prone to violence under social pressure, and also based on the situation-dependent effects of the social stressor, we suggest that chronic psychosocial stress leads to a behavioral profile akin to social phobia.