Developmental Language Disorder and Psychopathology : Disentangling Shared Genetic and Environmental Influences

There is considerable variability in the extent to which young people with developmental language disorder (DLD) experience mental health difficulties. What drives these individual differences remains unclear. In the current paper, data from the Twin Early Development Study were used to investigate the genetic and environmental influences on psychopathology in children and adolescents with DLD (n=325) and those without DLD (n=865). Trivariate ACE models were fitted to investigate aetiological influences on DLD and psychopathology and bivariate heterogeneity and homogeneity models were fitted and compared to investigate quantitative differences in aetiological influences on psychopathology between the groups. The genetic correlation between DLD and internalising problems in childhood was significant suggesting that their co-occurrence is due to common genetic influences. Similar, but non-significant effects were observed for externalising problems. In addition, genetic influences on internalising problems, but not externalising problems, appeared to be higher in young people with DLD than those without DLD suggesting that the presence of DLD may exacerbate genetic risk for internalising problems. These findings suggest that genetic influences on internalising problems may also confer susceptibility to DLD (or vice versa) and that DLD serves as an additional risk factor for those with a genetic predisposition for internalising problems.