Heritability of generalized anxiety stability: a longitudinal twin study among young adults

Despite the high prevalence of generalized anxiety among young adults, studies investigating factors that shape the course of these symptoms during the twenties are scarce. In addition, generalized anxiety can manifest in different ways, but it is unclear whether symptoms cluster under distinct dimensions in this age group. The current study addressed these gaps using data from the Twins Early Development Study. First, we examined genetic and environmental contributions to continuity and change in generalized anxiety symptoms in young adulthood and the heritability of a latent factor reflecting stability over this period. Next, to explore potential dimensions of generalized anxiety, we investigated the factorial structure of symptoms as well as etiological influences underpinning the different factors.

The sample comprised 6,429 twin pairs. Generalized anxiety was assessed at six waves (age 23-26 years).

Genetic factors largely accounted for continuity and environmental factors for change in symptom severity. Furthermore, the heritability of stable generalized anxiety (60%) was substantially higher than that at any single time point (39-46%). Regarding the factorial structure of symptoms, we found evidence of two dimensions: worry-avoidance and somatic-distress symptoms. Genetic correlations (rG = 0.77-0.91) between the two dimensions were higher than environmental correlations (rE = 0.26-0.65).

The current findings suggest that extracting temporal stability provides the strongest opportunity to identify genetic influences on generalized anxiety. Moreover, the results indicate that differences between generalized anxiety dimensions are more likely attributable to environmental than genetic effects.