Genetic and environmental influences on internalizing psychopathology vary as a function of economic status

Abstract

BackgroundDifferent theories of the link between socio-economic status (SES) and mental illness have been postulated. In particular, two theories of this association, social causation and social selection, differ in the implied causal pathway. The authors employ behavior genetic modeling to consider evidence for both social selection and social causation in the relationship between income variation and internalizing disorders.MethodBehavior genetic modeling was used to estimate the presence of gene–environment interaction (GxE, social causation) in the presence of gene–environment correlation (rGE, social selection). Participants were members of a sample of 719 twin pairs from the Midlife in the United States study. Four internalizing (INT) syndromes were assessed: major depression (MD); generalized anxiety disorder (GAD); panic attacks (PA); neuroticism (N). SES was measured with total family household income.ResultsOne factor best accounted for the variance shared between MD, GAD, PA and N. The etiology of variation in INT changed from high to low levels of income, with unique environmental factors playing a larger role in INT variation at lower levels of income. Across levels of income, rGE between income and INT was modest (low income ra=0.39 to high income ra=0.54), implying a selection process operating through genetic effects linking lower income with INT psychopathology.ConclusionsFindings support social causation by suggesting that low income contributes significantly to environmental variation in INT. Modest support was found for social selection, but should be extended using longitudinal designs. Effective interventions for internalizing psychopathology may differ depending on income.

What Money Can (and Can't) Buy: A Behavior Genetic Analysis of the Physical and Mental Health Benefits of Socioeconomic Advantage in Modern America

“…Indeed, nonshared environmental correlations were not statistically significant and tended to account for less than one-third of the total phenotypic correlation. These findings also dovetail with the existing behavior genetics research suggesting a non-causal link between socioeconomic status and internalizing Osler et al, 2007;South & Krueger, 2011;Strachan et al 2016;Tamb et al, 2012).…”

“…We summarize the extant research in detail in Chapter 1, but several highlights are noteworthy. First, the link between compositional and contextual SES and mental health is broad and spans many facets of mental well-being, including internalizing (Ansseau et al, 2007;Bøe et al, 2012;Gilman et al, 2002;Goodman, 1999;Green & Benzeval, 2013;Lemstra et al, 2008b;Lorant et al, 2003;Muramatsu, 2003;South & Krueger, 2011;Tambs et al, 2012;Zimmerman & Katon, 2005), neuroticism (Jonassaint et al, 2011;South & Krueger, 2011), externalizing (Amone-P' Olak et al, 2009;Bøe et al, 2012;Hsieh & Pugh, 1993;Huisman et al, 2010;National Center for Health Statistics, 2012), and serious mental illness and personality pathology (Hudson, 2005;Walsh et al, 2012). Second, this relationship appears to strengthen with age (Miech & Shanahan, 2000).…”

“…Third, existing behavior genetics research on the SESmental health gradient demonstrates that this relation is far more nuanced than correlational or natural experimental studies suggest. This association is rarely found to be causal and is instead attributable to family-level confounds, especially additive genetic selection factors Osler et al, 2007;South & Krueger, 2011;Strachan et al, 2016;Tambs et al, 2012). Fourth, the complexities of this phenomenon are further made evident by research demonstrating SES effects on variance in mental health.…”

“…Fourth, the complexities of this phenomenon are further made evident by research demonstrating SES effects on variance in mental health. Heritability of mental illness tends to be greater in more disadvantaged environments (South & Krueger, 2011;Strachan et al 2016;Tuvblad et al, 2006), although the mechanisms of this change varied across studies (i.e., changes in raw additive genetic variance as a function of SES versus changes in heritability; causal processes versus social selection processes). In studies using individual-level SES indicators (typically adult samples), the interaction between variance in mental health and SES appeared causal when the effect was on nonshared environmental variance (South & Krueger, 2011) and non-causal when SES acted on additive genetic factors (Strachan et al, 2016).…”

“…Anxiety symptoms (Ansseau et al, 2007;Lemstra et al, 2008b;Green & Benzeval, 2013;South & Krueger, 2011;Tambs et al, 2012) and neuroticism characteristics (Jonassaint, Siegler, Barefoot, Edwards, & Williams, 2011;South & Krueger, 2011) are similarly associated with lower SES across the lifespan. Socioeconomic factors (particularly parental education) are also implicated in externalizing problems in adolescents (Amone-P' Olak et al, 2009;Bøe et al, 2012;Huisman et al, 2010), including aggression (Amone-P'Olak et al, 2009), delinquency or misconduct (Amone-P' Olak et al, 2009;Bøe et al, 2012), and symptoms of attention-deficit/hyperactivity disorder (Amone-P' Olak et al, 2009;Bøe et al, 2012; National Center for Health Statistics, 2012).…”