Genetic and environmental influences on depressive symptoms by age and gender in African American twins

Abstract

Depression is typically considered relative to individuals and thought to originate from both biological and environmental factors. However, the environmental constraints and insults that African Americans experience likely influence the concordance by age and gender for depression scores among adult African American twins. Monozygotic (MZ) (n = 102) and Dizygotic (DZ) (n = 110) twins, age 25–88 years in the Carolina African American Twin Study of Aging were examined using an 11-item version of the CES-D measure of depressive symptomatology. Those participants with scores above nine were considered depressed. Overall, the MZ pairs had a higher concordance than the DZ pairs implying genetic influence. Both MZ and DZ males had higher concordances than either female zygosity groups. The difference between the concordance rates for MZ and DZ twin pairs was greater in males than females. By age group, the difference between the concordance rates for younger MZ and DZ twin pairs was much larger than for older pairs. The results suggest that, even though African Americans may be at risk for depression due to contextual/environmental factors, genetic influences remain important.

Keywords:

• African American
• twins
• heritability
• depressive symptomatology
• concordance
• aging

Acknowledgements

The CAATSA project was funded by a grant from the National Institute on Aging (grant #1RO1-AG13662-01A2) to the first author. The authors thank Sebrina Wiggins and Kimya I. Jackson for their assistance in the preparation of this manuscript.