The Center for Epidemiologic Studies-Depression scale was administered to 68 identical and 161 fraternal twin pairs reared apart and 114 identical and 138 fraternal pairs reared together to ascertain relative genetic and environmental contributions to individual differences in self-reported depressive symptoms. Intraclass correlations and model fitting indicated that genetic influences explained 16% of the variance in total depression scores and 19% for the Psychomotor Retardation and Somatic Complaints subscale, but heritability was minimal for the Depressed Mood and Well-Being subscales. Influence of family rearing context played a substantial role in explaining twin similarity, whereas unique life experiences accounted for the greatest proportion of variance. Significant age group differences were observed, with heritability greater in twins of 60 years of age or older than in twins under 60, especially for Psychomotor Retardation.
"These genetic influences are usually shown to account for 35–50% of the time-specific variance (heritability 1 ) in global happiness measures (Lykken and Tellegen 1996; Røysamb et al. 2002; Stubbe et al. 2005; Nes et al. 2005, 2006; Schnittker 2008), and somewhat less when well-being is measured as a state more than a trait (e.g. Gatz et al. 1992). This is probably due to the fact that global well-being measures to a greater extent reflect individual differences in dispositional positivity. "
[Show abstract][Hide abstract] ABSTRACT: A number of behaviour genetic studies have shown variation in happiness to be influenced by genes, and indicated that long-term
happiness is predominantly caused by genes. To policy makers and individuals, as well as the psychological and psychiatric
enterprise, evidence for considerable and stable genetic contributions suggests that societal changes, therapeutic interventions,
and public prevention may produce mainly transitory or minor effects. This is not true. The present paper aims to summarise
the recent behaviour genetic findings on happiness and happiness-related constructs and to discuss their theoretical and practical
implications. Specifically, five major implications relevant to public health work, are outlined and broadly discussed: (1)
high heritability does not limit chances for raising happiness, (2) genes generate stability, (3) environments generate change,
(4) environmental influences operate on an individual-by-individual basis, and (5) control for genetic endowments is necessary
for correct measures of environmental effects.
"Despite the majority of studies not indicating shared environmental effects, some studies show significant effects (e.g. Tellegen et al. 1988; Baker et al. 1992; Gatz et al. 1992; Weiss et al. 2002). Very large samples are also required for detection of moderate to small effects and the magnitude of the effects are likely to vary across development (Burt 2009). "
[Show abstract][Hide abstract] ABSTRACT: Biometric studies have shown that happiness is strongly affected by genes. The findings are mainly based on twin data, however, and the full validity of the results has been debated. To overcome some limitations in classical twin research, we examined aetiological sources of subjective well-being (SWB), using two independent population-based samples, one including nuclear families (N = 54,540) and one including twins (N = 6,620). Biometric modelling using R was conducted to test for a data structure implying either non-additive genetic effects or higher environmental co-twin correlation in MZ than DZ pairs (violation of the EEA). We also estimated non-random mating, cultural transmission and shared environments specific for regular siblings and twins. Two sets of nested models were fitted and compared. The best explanatory model shows that family matters for happiness predominantly due to quantitative sex-specific genetic effects, a moderate spousal correlation and a shared twin environment. Upper limits for broad-sense heritability were estimated to be 0.33 (females) and 0.36 (males). Our study constitutes the most elaborate biometric study of SWB to date and illustrates the utility of including responses from multiple types of relatives in quantitative genetic analyses.
"Our somewhat high heritability estimate is nonetheless in accordance with the findings from earlier studies, that heritability is usually higher for females than males (e.g. Jansson et al. 2004 ; Kendler et al. 2006b) and for an older than younger population (Gatz et al. 1992). Also, changes in gene expression over the life cycle, in which genetic systems switch off and on, have been invoked as explanations for fluctuations in heritability estimates across adult life (Carmelli et al. 2000). "
[Show abstract][Hide abstract] ABSTRACT: Prior studies suggest that certain types of personality are at higher risk for developing depressive disorders. This study examined the relationship between old age depressive symptoms and two middle-age personality dimensions, neuroticism and extraversion.
The present study is part of the Finnish Twin Study on Aging, where altogether 409 female twins who had completed the Eysenck Personality Inventory at the age of 38-51 years were studied for depressive symptoms 28 years later using Center for the Epidemiologic Studies Depression Scale. Logistic regression analysis suitable for dependent data and univariate and Cholesky models for decomposing the genetic and environmental factor were used.
Middle age extraversion protected from later depressive symptoms while neuroticism increased the risk. Twin modeling indicated that the association between neuroticism and depressive symptoms resulted from shared genetic risk factors common to both traits. However, a substantial proportion of the genetic vulnerability was specific to old age depressive symptoms and was not shared with neuroticism. Middle age extraversion had no genetic relationship with old age depressive symptoms.
The relationship between middle age neuroticism and old age depressive symptoms is strong but only partly the result of genetic factors that predispose to both neuroticism and depressive symptoms. Extraversion, by contrast, has no genetic relationship with depressive symptoms experienced in old age.
Psychological Medicine 10/2009; 40(8):1357-66. DOI:10.1017/S0033291709991401 · 5.94 Impact Factor
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