Background: Designed as state measures to monitor treatment response, symptoms of anxiety and depression (SxAnxDep) also have trait-like characteristics. No comprehensive etiologic model for SxAnxDep has illuminated the inter-relationship between their state- and trait-like characteristics, while including key predictor variables.
Method: In a prospective three-wave study of 2395 female twins from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders (VATSPSUD), we examined, using structural equation modeling, how genes, childhood and past-year environmental stressors, personality and episodes of major depression (MD) and generalized anxiety disorder (GAD) influence SxAnxDep.
Results: The best-fit model, which explained 68-74% of the variance in SxAnxDep, revealed two etiologic pathways. Stable levels of SxAnxDep resulted largely from neuroticism, which in turn was influenced by genetic and early environment risk factors. Occasion-specific influences resulted from stressful events mediated through episodes of MD or GAD. These two pathways, which had approximately equal influences on levels of SxAnxDep, were substantially correlated because the genetic, early environmental and personality factors that impacted on stable symptom levels also predisposed to event exposure and disorder onset. No significant interaction was seen between the two pathways.
Conclusions: SxAnxDep in women in the general population arise from two inter-related causal pathways. The first, the 'trait-like' pathway, reflects genetic and early environmental risk factors, and is mediated largely through personality. The second pathway is mediated through episodes of MD and GAD, and is the result of both recent environmental adversities and trait-like factors that influence event exposure and the probability of disorder onset.