Genetic and environmental origins of the co-occurrence of autistic traits, anxiety and depression: Evidence from meta-analysis and twin study.
BACKGROUND Prior twin studies have shown genetic and environmental overlap between autistic traits and internalising symptoms. However, it remains unknown whether this overlap reflects a common latent liability or similar aetiological influences operating through independent pathways. We investigated the genetic and environmental origins of the co-occurrence of autistic traits and internalising symptoms with a meta-analysis and an empirical twin study. METHODS Study 1 meta-analysed six twin studies examining autistic traits and internalising symptoms, predominantly in Western child and adolescent samples. Study 2 applied multivariate genetic modelling to a Chinese community sample of 178 twin pairs (109 monozygotic and 69 dizygotic, aged 24-35). RESULTS Study 1 showed genetic (rA = 0.42) and non-shared environmental (rE = 0.15) overlap between autistic traits and internalising symptoms, although substantial heterogeneity was observed across estimates. Study 2 was broadly consistent with the findings of Study 1. It further suggested that the co-occurrence of autistic traits, anxiety and depressive symptoms may be partly explained by a common latent factor shaped by genetic and non-shared environmental influences, although the common pathway model was only tentatively favoured over the independent pathway model. CONCLUSION Across meta-analytic and empirical twin studies, the co-occurrence of autistic traits, anxiety and depressive symptoms appears to be shaped in part by shared genetic and non-shared environmental influences across these three traits. This generally aligns with the transdiagnostic framework of psychopathology. It also highlights that individuals presenting autistic traits may benefit from screening for internalising symptoms, and vice versa.