Depressive vulnerability, stressful life events and episode onset of major depression: a longitudinal model

Abstract

Background: The nature of the relationship between depressive vulnerability (DV) and acute adversity in the etiology of major depression (MD) remains poorly understood.

Method: Stressful life events (SLEs) and MD onsets in the last year were assessed at four waves in cohort 1 (females) and at two waves in cohort 2 (males and females) from the Virginia Adult Twin Study. Structural equation modeling was conducted in Mplus.

Results: In cohort 1, DV was strongly indexed by depressive episodes over the four waves (paths from +0.72 to 0.79) and predicted by SLEs in the month of their occurrence (+0.31 to 0.36). Wave-specific DV was associated both with stable DV (+0.29 to 0.33) and by forward transmission of DV from the preceding wave (+0.33 to 0.36). SLEs were predicted by stable DV (+0.29) and from SLEs in the preceding month (+0.06). As the cohort aged, MD onsets were better indexed by DV and more poorly predicted by SLEs. Parameter estimates were similar in males and females from cohort 2. In individuals with prior depressive episodes, the association between MD onset and SLEs was weakened while the prediction of SLEs from DV was substantially strengthened. We found no evidence for 'reverse causation' from MD episodes to SLEs.

Conclusion: The interrelationship between DV and acute adversity in the etiology of MD is complex and temporally dynamic. DV impacts on MD risk both directly and indirectly through selection into high stress environments. Over time, depressive episodes become more autonomous. Both DV and SLEs transmit forward over time and therefore form clear targets for intervention.

Keywords: Adversity; major depression; stressful life events.

Fig. 1

Parameter estimates from our best-fitting model applied to four waves of interviews in cohort 1. For simplicity, we present only the first 2 months of the 12-month periods for each of the four waves. Each of the arrows represents standardized partial correlations. DV, Depressive vulnerability; MD, major depression; SLE, stressful life event. For MD onset and SLEs, the numbers in the boxes refer to wave and month in wave so that 1-01 reflects the first month in wave 1 and 4-02 the second month of wave 4. Variables in ellipses are latent while variables in rectangles are observed.

Fig. 2

Parameter estimates from our best-fitting model applied to (a) two waves of interviews in females from cohort 2, and (b) two waves of interviews in males from cohort 2. For abbreviations, see legend to Fig. 1.