The Heritability of Life Events: An Adolescent Twin and Adoption Study

Abstract

Although life events are often conceptualized as reflecting exogenous risk factors for psychopathology, twin studies have suggested they are heritable. We undertook a mixed twin/adoption study to further explore genetic and environmental contributions to individual differences in the experience of life events. Specifically, a sample of 618 pairs of like-sex adolescent twins, 244 pairs of like-sex adopted adolescent and young adult siblings, and 128 pairs of like-sex biological siblings completed a life events interview. Events were classified as independent (not likely to have been influenced by respondent's behavior), dependent (likely to have been influenced by respondent's behavior), or familial (experienced by a family member), and then summed to form three life event scales. Variance on the scales was assumed to be a function of four factors: additive genetic effects (a2), shared environmental effects (c2), twin-specific effects (t2), and nonshared environmental effects (e2). Data were analyzed using standard biometrical models. Shared environmental effects were found to be the largest contributor to variance in familial events (c2 = .71; 95% confidence interval of .65, .76); additive genetic effects were the largest contributor to dependent events (a2 = .45; CI = .31, .58); and nonshared environmental effects were found to be the largest contributor independent events (e2 = .57; CI = .51, .64). A significant twin-specific effect was also found for independent life events, indicating that twins are more likely to be exposed to such events than non-twin biological siblings. Findings are discussed in terms of their implication for understanding the nature of psychosocial risk.

Personality: bridging the literatures from human psychology and behavioural ecology

“…This has long been recognized within HPP (Buss 1987;Saudino et al 1997), and is increasingly recognized in BE (see Dingemanse et al 2010). Researchers have also shown that major life events in humans show substantial heritability (Bemmels et al 2008), suggesting that influences of personality variables on situational experience are ubiquitous.…”

Harsh times: do stressors lead to labor market losses?

“…First, previous studies have shown that environmental and genetic factors contribute differently to the variance of dependent and independent life events. In particular, dependent life events are explained by genetic factors for the most part, whereas shared and unshared environmental factors are a larger contributor to the variance in independent life events (Bemmels et al, 2008). Second, men and women are distressed by distinctly different types of adverse events.…”

“…Researchers have distinguished independent and dependent life events (Bemmels et al, 2008). Some shocks, such as the death of a spouse or other close relative are independent and outside of any one person's control.…”

“…For example, early life conditions may exposure to shocks and have an influence on earnings and employment outcomes. There is also evidence that exposure to dependent life events is substantially influenced by genetic factors (Bemmels et al, 2008). Second, individuals react in different ways to negative life events.…”

Building on Progress: Expanding the Research Infrastructure for the Social, Economic, and Behavioral Sciences

“…The list of dependent variables of social science interest for which genetic effects or gene-environment interactions have been reported is growing daily: from the frequency of life events (Bemmels et al 2008) to economic decision making (Zhong et al 2009) and the preference for coffee (Vink et al 2009). Particularly interesting are genetic variations that correlate with numerous dependent behavioral variables.…”