78. McGuire, S., & Clifford, J. (2000). Genetic and environmental contributions to loneliness in children. Psychological Science, 11, 487-491.

Data were collected using both an adoption design and a twin-sibling design in which children participating in the Colorado Adoption Project completed a general loneliness scale at ages 9, 10, 11, and 12 years and in the San Diego Sibling Study completed a scale assessing loneliness at school between the ages of 8 and 14. Both studies showed significant heritability and nonshared environmental influences for children's loneliness.