African-American representation in family and twin studies of mood and anxiety disorders: A systematic review

- African Americans (AA) underrepresented in family & twin studies of affective disorders.
- Despite some improvement over a 35-year period, this underrepresentation persists.
- To date, there are no family studies of mood disorders in AA.
- To date, there are no twin studies of anxiety disorders in AA.

PurposeMood and anxiety disorders are common and disabling psychiatric disorders with known heritable risk factors. But the extent to which their heritability and familial risks can be generalized across ethnic/racial groups is still largely unknown, but remains of considerable scientific and clinical interest. The main objective in this review was to evaluate African-American (AA) representation in family and twin studies of major mood and anxiety disorders.MethodWe conducted key word-driven computerized searches in MEDLINE and PsycINFO and manual searches from reference lists of selected articles. Search parameters included family or twin studies, mood or anxiety disorders, and familial aggregation or heritability. US-based studies published from 1980 to 2015 were included.ResultsThe final selection yielded 209 studies, of which 88 did not report race/ethnicity or only reported Caucasian/white race. Of the remaining 121 studies, 66% did not include AAs, 24% included 1-10% AA, 8% included greater than 10% AA and 2 studies were exclusively AA. These trends were similar across study type, disorder and time periods spanning 35 years.LimitationsSmall samples, including the large number of studies without race/ethnicity reports, limited detailed analyses of change across time by disorder and study type. Adoption studies were not included in this review.ConclusionsUnderrepresentation of AAs in family and twin studies of affective disorders is substantial and can limit generalizability of established heritability and familial risk estimates across clinical and research settings. Additional twin and family studies focusing on AAs can be of benefit in closing this gap.