Exploring the covariation between anxiety and depression symptoms: A genetic analysis of the effects of age and sex

Self-reported anxiety and depression symptoms in children and adolescents h ave been shown to be heritable, and are also highly correlated. Furthermore , there have been indications in the literature of sex and age differences in the aetiologies of these two types of symptoms. This study set out to as certain to what extent the generic and environmental factors that influence anxiety symptoms also influence depression symptoms, and whether these are the same in children and adolescents, and males and females. Four hundred and ninety pairs of twins aged 8 to 16 years completed the Children's Depre ssion Inventory and the Trait scale of the Stale-Trait Anxiety Inventory fo r Children. There were significant effects of age and sex on the variance i n and covariance between these two types of symptom. Bivariate genetic anal yses of the measures indicated that the genetic influences on anxiety and d epression were shared for all four groups, a finding that has been consiste ntly demonstrated for adults.