Genetic and environmental influences on social support: the Swedish Adoption/Twin Study of Aging.

A new direction in behavioral genetic research is the exploration of genetic influences on ostensibly environmental measures. The goal of the present study was to identify genetic as well as environmental influences that contribute to an individual's motivation and ability to create and maintain social support systems during the second half of the life course. One of the most powerful behavioral genetic designs is the combined twin/adoption design which is used in the Swedish Adoption/Twin Study of Aging (SATSA). A subsample of 424 pairs of twins age 50 and above was used: 64 pairs of identical twins reared apart, 95 pairs of identical twins reared together, 132 pairs of fraternal twins reared apart, and 133 pairs of fraternal twins reared together. The measure of social support assessed both the quantity of relationships as well as the perceived adequacy of the social support network. Model-fitting analyses verified the importance of genetic factors for perceived adequacy of the social support network, whereas little genetic influence was found for the quantity of social relationships.