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.

Genome-Wide Association Study (Gwas) and Genome-Wide by Environment Interaction Study (Gweis) of Depressive Symptoms in African American and Hispanic/Latina Women

“…Extending genetic association studies to more diverse racial/ethnic populations – especially of women – is therefore needed. These studies are likely to be informative, as depression appears at least as heritable (around 40%) among African Americans 22,23 and Hispanics 24 compared to European Americans 1 . Such extensions are also important given known racial/ethnic (as well as sex) disparities.…”

Growing Old but Not Growing Apart: Twin Similarity in the Latter Half of the Lifespan

“…Similarly, in a longitudinal study of 187 twin pairs initially aged 59–70, Carmelli et al (2000) reported that the heritability of a quantitative index of depression symptomatology increased from 25 % at baseline to 55 % at 10-year follow-up. Alternatively, rather than an increase in heritability with age, Whitfield et al (2008) reported that the heritability of liability to a categorical indicator of depression decreased from 28 % for twins 49 years and younger to 6 % for twins 50 years and older in a sample of 212 twin pairs. Finally, Neiss and Almeida (2004) reported evidence of both increases and decreases in heritable influences on different measures of psychological distress from a single sample of 210 pairs of twins age 25–74 years from the National Survey of Midlife in the United States Survey (MIDUS).…”

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

“…There were 12 studies in which AA representation exceeded 10% of the sample – including two studies focusing exclusively on AA (Chapman et al, 2012; Whitfield et al, 2008) (Table 2). Ten of the 12 studies shown in Table 2, had AA proportions ranging from 11% to 24% of their samples.…”

“…The second study focusing exclusively on AA was a twin study on the heritability of depressive symptoms as measured by the Center for Epidemiologic Studies-Depression Scale (CES-D), using a sample of 212 twins (Whitfield et al, 2008). The study used cutoff points to dichotomize the CES-D scores into “depressed” vs. “non-depressed” to obtain heritability estimates.…”

“…This increase was driven by a number of twin studies published between 2008 and 2015, including the one study that focused exclusively on AA (Whitfield et al, 2008), and a second study in which AA represented 15% of the sample (Duncan et al, 2014). Despite some methodological limitations in the first study, such as assessing depressive symptoms in recent weeks (as opposed to lifetime DSM-diagnosed disorder), and not establishing independence of co-twin interviews, we consider noteworthy the findings of age and gender differences in heritability, contrasting findings from the earlier-published twin studies that found no age/gender differences.…”