Sources of variability in John Henryism

OBJECTIVES: To decompose sources of individual differences in coping as measured by John Henryism among African Americans. METHODS: Analyses described in this study are based on the pairwise responses from 180 pairs of same-sex, African-American twin pairs who participated in the Carolina African-American Twins Study of Aging (CAATSA). The sample consisted of 85 monozygotic (MZ) and 95 dizygotic (DZ) twin pairs. RESULTS: Environmental factors account for most of the variance (65%) in John Henryism scores, with the remaining variance attributable to additive genetic factors (35%). The test of the genetic component suggested that the 35% represented a statistically significant proportion of variance. CONCLUSIONS: The vast majority of recent studies on African Americans and health outcomes have focused on the impact of psychosocial factors on diseases such as hypertension and diabetes, with relatively little attention to possible genetic contributors. Previous research on psychosocial indices and their relationship to cardiovascular health among African Americans has focused on assessment and epidemiological explorations rather than understanding the etiology of variability in such measures.