Genetic and Environmental Associations Between Depressive Symptomatology and Loneliness in Adulthood

The conceptual and symptom overlap between depression and loneliness is so strong that depressive symptom rating scales often include measures of loneliness and their linear association ranges between .40 and .68. Despite these findings, few genetically informed studies have investigated the genetic and environmental association between them. In this brief report, we used 416 individual twins, 229 MZ twins and 187 DZ twins, from the Louisville Twin Study (MAge = 48.17; 56% female) to test two hypotheses: first, depressive symptomatology and loneliness are correlated genetically and environmentally; and second, the genetic correlation in women would be larger than men. Results from a correlated ACE factors model indicate that the genetic correlation is .52 and the nonshared environmental correlation is .27. No sex differences were observed. The strong genetic overlap between depressive symptomatology and loneliness raises questions about the biological mechanisms associated with common sets of genes.