Leisure activity engagement and depressive symptoms: Meta-analysis of 11 studies of middle-aged and older twins aged 32-99

Background Leisure activity is associated with a wide range of physical and mental health outcomes. Nonetheless, the causal basis for these associations is uncertain and we do not fully understand why some individuals are active while others are sedentary. Methods We investigated genetic and environmental contributions to individual differences in the frequency of social, physical, and intellectual leisure activities and their relationship to depressive symptoms, using data from the Interplay of Genes and Environment across Multiple Studies (IGEMS) consortium. The sample consisted of 31,596 like-sex twins (44.1% monozygotic, 31.4% women, age range 32 to 99 years) representing 11 studies from Sweden, Denmark, USA, and Australia. Results Results indicated moderate contributions of genetic factors to social (a2 = 0.26, 95% CI = 0.16; 0.35), physical (a2 = 0.39, CI = 0.28; 0.51), and intellectual (a2 = 0.47, CI = 0.33; 0.61) activities. The contribution of shared environmental factors (c2) was trivial, ranging from -0.03 to 0.02, while estimates of non-shared environmental factors (e2) were consistently substantial, ranging from 0.52 to 0.68. There was no evidence that estimates varied by age and limited evidence that they varied by sex and country. Co-twin control analyses revealed a significant negative within-pair association of depressive symptoms with each activity domain. Conclusions Although genetic factors make important contributions to mid-to-late-life activity levels, associations of leisure activity levels with depressive symptoms remained significant when controlling for (unmeasured) genetic and shared environmental confounding. These findings are consistent with, albeit not proof of, a causal effect of leisure activities on depressive symptoms. This finding highlights the utility of the co-twin control design.