The Mediating Effect of Stress Reactivity in the 18-Year Bidirectional Relationship Between Generalized Anxiety and Depression Severity

Background: Generalized anxiety disorder (GAD) and major depressive disorder (MDD) often precede and predict one another. Stress reactivity theories of psychopathology posit that patterns of heightened emotional reactions to stressors can result in increased vulnerability to the development of anxiety and depression. However, cross-sectional studies on this topic have hindered causal inferences. Method: The present study examined stress reactivity as a potential mediator of the sequential associations between GAD and MDD symptoms in a sample of 3,294 community-dwelling adults. GAD and MDD symptom severity (Composite International Diagnostic Interview-Short Form) was assessed at two time points (T1 and T3), approximately 18 years apart. Stress reactivity (Multidimensional Personality Questionnaire) was measured at T2. Results: Structural equation mediation modeling demonstrated that higher T1 GAD severity positively predicted more severe T3 MDD symptoms via T2 stress reactivity (d = 0.45–0.50). After controlling for T1 GAD, T2 stress reactivity was not a significant mediator in the relationship between higher T1 MDD symptoms and worse T3 GAD symptoms. Direct effects indicated that T1 GAD positively predicted T3 MDD 18 years later, and vice versa (d = 1.29–1.65). Limitations: Stress reactivity was assessed using a self-report measure, limiting conclusions to perceived (vs. behaviorally indexed) stress reactivity. Conclusions: These findings indicate that stress reactivity may be one mechanism through which GAD leads to later MDD over prolonged durations. Overall, our results suggest that targeting stress reactivity in treatments for GAD may reduce the risk of developing subsequent MDD.