The impact of genes and environment assessed longitudinally on psychological and somatic distress in twins from ages 15 to 35 years.

Abstract

Background: Genetically informative twin studies have consistently found that individual differences in anxiety and depression symptoms are stable and primarily attributable to time-invariant genetic influences, with non-shared environmental influences accounting for transient effects.

Methods: We explored the etiology of psychological and somatic distress in 2279 Australian twins assessed up to six times between ages 12-35. We evaluated autoregressive, latent growth, dual-change, common, and independent pathway models to identify which, if any, best describes the observed longitudinal covariance and accounts for genetic and environmental influences over time.

Results: An autoregression model best explained both psychological and somatic distress. Familial aggregation was entirely explained by additive genetic influences, which were largely stable from ages 12 to 35. However, small but significant age-dependent genetic influences were observed at ages 20-27 and 32-35 for psychological distress and at ages 16-19 and 24-27 for somatic distress. In contrast, environmental influences were predominantly transient and age-specific.

Conclusions: The longitudinal trajectory of psychological distress from ages 12 to 35 can thus be largely explained by forward transmission of a stable additive genetic influence, alongside smaller age-specific genetic innovations. This study addresses the limitation of previous research by exhaustively exploring alternative theoretical explanations for the observed patterns in distress symptoms over time, providing a more comprehensive understanding of the genetic and environmental factors influencing psychological and somatic distress across this age range.