Kindling of Life Stress in Bipolar Disorder: Comparison of Sensitization and Autonomy Models and Integration with Emerging Biopsychosocial Theories

Abstract

Most life stress literature in bipolar disorder (BD) fails to account for the possibility of a changing relationship between psychosocial context and episode initiation across the course of the disorder. The kindling hypothesis states that over the longitudinal course of recurrent affective disorders, there is a weakening temporal relationship between major life stress and episode initiation (Post, 1992). This process could reflect either a progressive sensitization or a progressive autonomy (i.e., insensitivity) to life stress. The present study aimed to test the kindling model in BD by examining the effect of lifetime mood episodes on the relationship between proximal life events and prospectively assessed mood episodes. Polarity-specific tests of the model were conducted across the continuum of event severity, with respect to both impact and frequency of life events. Moreover, examination of the kindling hypothesis was embedded in the context of two emerging biopsychosocial theories of BD: the expanded Behavioral Approach System Dysregulation Model and the Circadian and Social Rhythm Theory. Data from 278 participants (146 bipolar spectrum participants and 132 normal control participants) were collected as part of the Temple-Wisconsin Longitudinal Investigation of Bipolar Spectrum Project. Hypotheses were polarity- and event-type specific and were in line with a stress sensitization model of bipolar spectrum disorders (BSD), rather than a stress autonomy model. Results partially supported a sensitization model: there was a decreased frequency and an increased impact of major events, and an increased frequency and impact of minor events. However, results for specific polarities and event types were not fully consistent with a stress sensitization model. Implications of these findings are addressed, followed by a discussion of study strengths, limitations, and promising directions for future research.