Genetic and environmental contributions to loneliness in children.

This report presents the results of the first behavioral genetic studies of children's loneliness. Data were collected using both an adoption design and a twin-sibling design. As part of the Colorado Adoption Project, 133 sibling pairs (69 biologically related pairs and 64 unrelated pairs in adoptive families) completed a general loneliness scale when they were 9, 10, 11, and 12 years old. As part of the San Diego Sibling Study, 142 sibling pairs (22 monozygotic twin, 40 dizygotic twin, and 80 full-sibling pairs) between the ages of 8 and 14 years old completed a scale assessing loneliness at school. Both studies showed significant heritability and nonshared environmental influences for children's loneliness.