Genetic and environmental effects on self-reported depressive symptoms in a general population twin sample

A population-based twin study of the symptomatic diagnostic criteria for major depression that occur within versus outside of major depressive episodes

BACKGROUND

Are genetic risk factors for current depressive symptoms good proxies for genetic risk factors for syndromal major depression (MD)?

METHODS

In over 9000 twins from the population-based Virginia Adult Twin Study of Psychiatric and Substance Use Disorders, the occurrence of all nine DSM symptomatic criteria for MD in the last year was assessed at personal interview and then grouped by their temporal co-occurrence. The DSM criteria which occurred outside (OUT) v. inside of (IN) MD episodes were then separated. We calculated tetrachoric correlations for OUT and IN depressive criteria in monozygotic (MZ) and dizygotic (DZ) pairs and fitted univariate and bivariate ACE twin models using OpenMx.

RESULTS

The mean twin correlations (±95% CIs) for IN depressive criteria were substantially higher than for OUT depressive criteria in both MZ [+0.35 (0.32-0.38) v. 0.20 (0.17-0.24)] and DZ pairs [0.20 (0.17-0.24) v. 0.10 (0.04-0.16]. The mean IN-OUT cross-correlation in MZ and DZ pairs was modest [+0.15 (0.07-0.24) and +0.07 (0.03-0.12)]. The mean heritability estimates for the nine In v. Out depressive criteria was 0.31 (0.22-0.41) and 0.15 (0.08-0.21), in MZ and DZ pairs, respectively. The mean genetic correlation between the nine IN and OUT depressive criteria was +0.07 (-0.07 to 0.21).

CONCLUSIONS

Depressive criteria occurring outside depressive episodes are less heritable than those occurring within. These two ways criteria can manifest are not closely genetically related. Current depressive symptoms - most of which are occurring outside of depressive episodes - are not, for genetic studies, good proxies for MD.

One water-soluble polysaccharide from Ginkgo biloba leaves with antidepressant activities via modulation of the gut microbiome

By performing a pyrosequencing-based analysis of bacterial community, we detected that one Ginkgo biloba polysaccharide reversed depression-associated gut dysbiosis and increased the richness of Lactobacillus species which has been proven to be a path to relieve depression.

Relevance of Rodent Models of Depression in Clinical Practice: Can We Overcome the Obstacles in Translational Neuropsychiatry?

The diagnosis of a mental disorder generally depends on clinical observations and phenomenological symptoms reported by the patient. The definition of a given diagnosis is criteria based and relies on the ability to accurately interpret subjective symptoms and complex behavior. This type of diagnosis comprises a challenge to translate to reliable animal models, and these translational uncertainties hamper the development of new treatments. In this review, we will discuss how depressive-like behavior can be induced in rodents, and the relationship between these models and depression in humans. Specifically, we suggest similarities between triggers of depressive-like behavior in animal models and human conditions known to increase the risk of depression, for example exhaustion and bullying. Although we acknowledge the potential problems in comparing animal findings to human conditions, such comparisons are useful for understanding the complexity of depression, and we highlight the need to develop clinical diagnoses and animal models in parallel to overcome translational uncertainties.

Genetic and Environmental Relationships Between Depressive and Anxiety Symptoms and Cardiovascular Risk Estimates Among Korean Twins and Families

We aimed to assess shared genetic correlations of depressive and anxiety symptoms with concurrent and future estimated cardiovascular risk (CVR) score in Korean twins and family members. For the relationship with Adult Treatment Panel III CVR estimate in subjects aged 30-74 years (n = 1,059, baseline and follow-up after 3.2 ± 1.2 years), Center for Epidemiological Studies Depression Scale (CES-D) and state and trait anxiety inventory (SAI and TAI) were measured at baseline. A mixed linear model for CVR scores at baseline and follow-up was applied to include depressive and anxiety symptoms, twin and family effects, income, education, alcohol use, exercise, body mass index, and baseline CVR score for follow-up analysis. Higher CES-D scores were associated with higher CVR score at baseline in men, while higher TAI score was associated with higher CVR score at follow-up in women. Heritabilities were 0.245~0.326 for CVR score, 0.320 for CES-D score, 0.367 for TAI score, and 0.482 for SAI score. There were significant common genetic correlations in the relationships of CES-D, TAI, and SAI scores with CVR scores at baseline and follow-up (after adjusting for baseline CV risk score). Shared common environmental correlations were observed in the relationships of CES-D and SAI scores with CVR score at baseline; and SAI score with CVR score at follow-up. In the within-monozygotic twin analysis, there were no associations between CES-D, TAI, and SAI scores, and CVR score. In conclusion, shared genetic and environmental influences were observed in the relationship between depressive and anxiety symptoms with concurrent and future CVR estimates.

Genetic and Environmental Contributions to Functional Connectivity Architecture of the Human Brain

One of the grand challenges faced by neuroscience is to delineate the determinants of interindividual variation in the comprehensive structural and functional connection matrices that comprise the human connectome. At present, this endeavor appears most tractable at the macroanatomic scale, where intrinsic brain activity exhibits robust patterns of synchrony that recapitulate core functional circuits at the individual level. Here, we use a classical twin study design to examine the heritability of intrinsic functional network properties in 101 twin pairs, including network activity (i.e., variance of a network's specific temporal fluctuations) and internetwork coherence (i.e., correlation between networks' specific temporal fluctuations). Five of 7 networks exhibited significantly heritable (23.3–65.2%) network activity, 6 of the 21 internetwork coherences were significantly heritable (25.6–42.0%), and 11 of the 21 internetwork coherences were significantly influenced by common environmental factors (18.0–47.1%). These results suggest that the source of interindividual variation in functional connectome has a modular architecture: individual modules represented by intrinsic connectivity networks are genetic controlled, while environmental factors influence the interplays between the modules. This work further provides network-specific hypotheses for discovery of the specific genetic and environmental factors influencing functional specialization and integration of the human brain.

The heritability of mental health and wellbeing defined using COMPAS-W, a new composite measure of wellbeing

Mental health is not simply the absence of mental illness; rather it is a distinct entity representing wellness. Models of wellbeing have been proposed that emphasize components of subjective wellbeing, psychological wellbeing, or a combination of both. A new 26-item scale of wellbeing (COMPAS-W) was developed in a cohort of 1669 healthy adult twins (18-61 years). The scale was derived using factor analysis of multiple scales of complementary constructs and confirmed using tests of reliability and convergent validity. Bivariate genetic modeling confirmed its heritability. From an original 89 items we identified six independent subcomponents that contributed to wellbeing. The COMPAS-W scale and its subcomponents showed construct validity against psychological and physical health behaviors, high internal consistency (average r=0.71, Wellbeing r=0.84), and 12-month test-retest reliability (average r=0.62, Wellbeing r=0.82). There was a moderate contribution of genetics to total Wellbeing (heritability h(2)=48%) and its subcomponents: Composure (h(2)=24%), Own-worth (h(2)=42%), Mastery (h(2)=40%), Positivity (h(2)=42%), Achievement (h(2)=32%) and Satisfaction (h(2)=43%). Multivariate genetic modeling indicated genetic variance was correlated across the scales, suggesting common genetic factors contributed to Wellbeing and its subcomponents. The COMPAS-W scale provides a validated indicator of wellbeing and offers a new tool to quantify mental health.

Depression, antidepressants, and falls among community-dwelling elderly people: the MOBILIZE Boston study

BACKGROUND

The mechanisms linking falls and depression are still unknown. The aim of the study is to examine the association between depression and antidepressants, with indoor and outdoor falls, and to investigate how antidepressants mediate this relationship.

METHODS

The study included 763 men and women aged 70 and older with baseline measures for depression and antidepressant use are captured with prospective data on falls from the "Maintenance of Balance, Independent Living, Intellect and Zest in the Elderly" (MOBILIZE) Boston study, which is a population-based longitudinal study (from 2005 to 2009).

RESULTS

Overall, the rate of falls was 26 falls/100 person-years. Seventeen percent of participants had clinically significant depressive symptoms (CSDS), and 12% used antidepressants. CSDS increased the risk of indoor and outdoor falls (incidence rate ratio [IRR] = 1.6, 95% confidence interval [CI] = 1.2-2.3, p < .01; IRR = 1.6, 95% CI = 1.2-2.2, p < .01). Antidepressant use increased the risk of outdoor falls by 70% and partially mediated the association between CSDS and outdoor falls (IRR = 1.7, 95% CI = 1.2-2.5, p < .05). There was no relationship between antidepressant use and indoor falls. Similar results were observed when depression was considered as a continuous variable.

CONCLUSIONS

Depression increased the risk of indoor and outdoor falls. Antidepressant use among older adults with CSDS increased the risk of outdoor, but not indoor falls. Clinicians should carefully consider the role of antidepressants among older adults with CSDS and their potential increase for the risk of outdoor falls.

Preadolescent anxiety: an epidemiological study concerning an Italian sample of 3,479 nine-year-old pupils

The epidemiology of anxiety traits was examined in a large sample of Italian preadolescent children, and 3,479 Italian nine-year-old subjects were enrolled. Anxious traits were observed in 10.5% of children. No significant gender differences were found, but children of separated couples presented a relative risk for anxious traits that was 50% higher, than children of cohabiting or married parents. Moreover, large families (more than 4 members) with a stay-at-home mother were also associated with anxiety in the offspring. Currently, this is the first study carried out in a large sample of preadolescent children, all of the same age.

A longitudinal etiologic model for symptoms of anxiety and depression in women

BACKGROUND

Designed as state measures to monitor treatment response, symptoms of anxiety and depression (SxAnxDep) also have trait-like characteristics. No comprehensive etiologic model for SxAnxDep has illuminated the inter-relationship between their state- and trait-like characteristics, while including key predictor variables.

METHOD

In a prospective three-wave study of 2395 female twins from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders (VATSPSUD), we examined, using structural equation modeling, how genes, childhood and past-year environmental stressors, personality and episodes of major depression (MD) and generalized anxiety disorder (GAD) influence SxAnxDep.

RESULTS

The best-fit model, which explained 68-74% of the variance in SxAnxDep, revealed two etiologic pathways. Stable levels of SxAnxDep resulted largely from neuroticism, which in turn was influenced by genetic and early environment risk factors. Occasion-specific influences resulted from stressful events mediated through episodes of MD or GAD. These two pathways, which had approximately equal influences on levels of SxAnxDep, were substantially correlated because the genetic, early environmental and personality factors that impacted on stable symptom levels also predisposed to event exposure and disorder onset. No significant interaction was seen between the two pathways.

CONCLUSIONS

SxAnxDep in women in the general population arise from two inter-related causal pathways. The first, the 'trait-like' pathway, reflects genetic and early environmental risk factors, and is mediated largely through personality. The second pathway is mediated through episodes of MD and GAD, and is the result of both recent environmental adversities and trait-like factors that influence event exposure and the probability of disorder onset.

The impact of environmental experiences on symptoms of anxiety and depression across the life span

Symptoms of anxiety and depression are relatively stable over time. Can this stability be explained by genetic influences, or is it caused by the long-lasting effects of accumulating environmental experiences? To address this question, we analyzed longitudinally assessed symptoms of anxiety and depression in eight samples of monozygotic twins of widely varying ages. These samples were drawn from American and European population-based registries. Using hierarchical linear modeling, we examined individual differences and individual changes in the level of symptoms over time. This method enabled us to decompose the variance into the predictable variance shared by both members of each pair of twins, the differences between individuals within pairs, and the residual variance. We then modeled how these components of individual variation changed over time. Within pairs, the twins' predicted levels of symptoms increasingly diverged from childhood until late adulthood, at which point the divergence ceased. By middle adulthood, environmental experiences contributed substantially to stable and predictable interindividual differences in levels of anxiety and depression.

Strong genetic correlation between interview-assessed internalizing disorders and a brief self-report symptom scale

Self-report scales for symptoms of anxiety and depression are frequently used for screening and research purposes. A moderate phenotypic association between disorders measured by diagnostic interviews and symptoms of anxiety and depression measured by self-report scales has been shown, but little is known about the overlap in these phenotypes' genetic and environmental variance. In the present study, we used twin modeling to identify common genetic and environmental liabilities underlying the phenotypic association between the self-report Symptom Checklist-5 (SCL-5) and lifetime internalizing disorders derived from the Composite International Diagnostic Interview (CIDI). The sample consisted of 7,992 young adult twins from the Norwegian Institute of Public Health Twin Panel (NIPHT), who all responded to a questionnaire. A subset of 2,793 individuals later underwent structured interviews. The best fitting model showed a strong genetic correlation of 0.82 (95% confidence interval; 0.61-1.0) between current self-report symptoms of anxiety and depression, and lifetime internalizing disorders, which suggests an almost complete overlap in genetic liability. The correlation between environmental factors was much lower: 0.16 (0.00-0.34, 95% CI). This implies that brief self-report scales capture genetic variance that is highly overlapping with the genetic variance common to internalizing disorder diagnoses. It thus follows that SCL-5 and similar instruments may be used as screening instruments for genetic risk factors that influence liability to internalizing disorders. In addition, existing data on self-report symptoms of anxiety and depression can be used with increased confidence to specify models including effects from genes coding for internalizing disorders.

Common genes contribute to depressive symptoms and heart rate variability: the Twins Heart Study

Depression and reduced heart rate variability (HRV) are predictors of coronary artery disease (CAD), and highly correlated with each other. However, little is known to what extend this correlation can be explained by common genetic components. We examined 198 middle-aged male twins (121 monozygotic and 77 dizygotic) from the Vietnam Era Twin Registry. Current depressive symptoms were assessed using the Beck Depression Inventory-II and HRV was assessed on 24-hour electrocardiographic Holter recordings. Five frequency domain variables were used, including ultra low frequency (ULF), very low frequency (VLF), low frequency (LF), high frequency (HF) and total power (TPow). Structural equation modeling was used to estimate shared genetic effects for depressive symptoms and the HRV frequency domains. Both depressive symptoms (h(2)=.5) and all measurements of HRV showed high heritability (h(2)=.43-.63). A significant inverse correlation was found between depressive symptoms and all HRV indices except LF and HF, with the highest coefficient (r) for TPow (r = -.24, P = .01) and ULF (r = -.24, P = .01). Bivariate genetic modeling revealed significant genetic correlations between depressive symptoms and TPow (r(A) = -.21, P = .04), as well as ULF (r(A) = -.23, P = .02). Of the total covariance between depressive symptoms and these two HRV indices, over 80% was due to the same genetic factors. In conclusion, depressive symptoms are associated with decreased HRV and this association is due, in large part, to a shared genetic effect. These results suggest that a common neurobiological dysfunction links depression and autonomic dysregulation.

Heritability of depressive symptoms: a case study using a multilevel approach

We present a case study using a multilevel modeling approach to determine whether depressive symptoms are affected by genetic factors. Existing studies examining this question have focused on twins. The present study built on the literature by conducting a preliminary study of the heritability of depressive symptoms within extended families. At the same time, this study assessed the need for adjustment of a heritability measure in a family study using a multigenerational sample. The sample consisted of 230 community-dwelling extended families that included 431 adult offspring, comprising full siblings, half siblings and cousins that participated in the University of Southern California Longitudinal Study of Generations. All participants filled out the Center for Epidemiologic Studies Depression (CES-D) scale. The multilevel analysis allowed us to model the natural hierarchy of the extended family. Results indicate that the proportion of the phenotypic variance for CES-D that occurs due to genetic differences is not significantly larger than zero among these participants [h(2) = 8.6%, 95% confidence interval (CI) = 0-57%, p = 0.71]. Our findings suggest that future studies examining depressive symptoms in this sample can focus on non-genetic explanatory factors without the necessity to control for genetic variation. However, our study may be limited by measurement of prevalent depressive symptoms, which may not generalize to lifetime depressive symptoms.

Common genetic contributions to depressive symptoms and inflammatory markers in middle-aged men: the Twins Heart Study

OBJECTIVE

To examine the extent to which a common genetic pathway is also involved in the relationship between depressive symptoms, in the absence of major depressive disorder (MDD), and inflammation. Recent data suggested that MDD and inflammation share common genes.

METHODS

We recruited 188 male twins from the Vietnam Era Twin Registry who were free of symptomatic coronary artery disease and MDD, with mean +/- standard deviation (SD) age of 55 +/- 2.75 years, including 54 monozygotic and 40 dizygotic twin pairs. These pairs were assessed for two inflammatory markers, interleukin (IL)-6 and C-reactive protein (CRP). Current depressive symptoms were measured with the Beck Depression Inventory-II. Generalized estimating equations were used to examine the phenotypic association between depression and inflammatory markers. Biometrical genetic modeling was performed to estimate the genetic and environmental contributions to this association.

RESULTS

An association was observed between severity of current depressive symptoms and increased levels of inflammatory markers (p < .001 for IL-6 and p = .005 for CRP). After adjustment for other factors, the association was slightly attenuated but remained statistically significant for IL-6 (p = .002). The heritability of IL-6, CRP, and depressive symptoms were estimated as 0.37, 0.65, and 0.48, respectively. Genetic modeling found a significant genetic correlation between IL-6 and depressive symptoms (r(G) = 0.22, p = .046), indicating that about 66% of the covariance between them can be explained by shared genetic influences.

CONCLUSIONS

Current depressive symptoms are significantly correlated with inflammatory markers. This covariation is due, in large part, to genes that are common to depressive symptoms and inflammation.

Depression and internally directed aggression: genetic and environmental contributions

This study uses behavior genetic (BG) methodology to investigate Freud's theory of depression as aggression directed toward the self (1930) and the extent to which genetically and environmentally influenced aggressive tendencies contribute to depressive symptoms. Data from the Twin and Offspring Study in Sweden (TOSS) is used to demonstrate how, in estimating shared and unique environmental influences, BG methods can inform psychoanalytic theory and practice, particularly because of their shared emphasis on the importance of individual experience in development. The TOSS sample consists of 909 pairs of adult twins, their partners, and one adolescent child per couple. The Center for Epidemiologic Studies Depression Scale (Radloff 1977) was used to measure depressive symptoms and the Karolinska Scales of Personality (Schalling and Edman 1993) to measure internally directed aggression. Genetic analyses indicated that for both men and women, their unique experiences as well as genetic factors contributed equally to the association between internally directed aggression and depressive symptoms. These findings support Freud's theory that constitutionally based differences in aggression, along with individual experiences, contribute to a person's depressive symptoms. Establishing that an individual's unique, not shared, experiences and perceptions contribute to depressive symptoms and internally directed aggression reinforces the use of patient-specific treatment approaches implemented in psychoanalytic psychotherapy or psychoanalysis.

Genetic and environmental influences on depressive symptoms by age and gender in African American twins

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.

A monozygotic twin differences study of nonshared environmental influence on adolescent depressive symptoms

The monozygotic (MZ) twin differences method was used to examine nonshared environmental aspects of the association of parenting (punitive and constructive discipline), negative life events (independent and dependent), and peers (antisocial and prosocial) with adolescent depressive symptoms in terms of sequelae, risk, and maintaining factors. Two self-report booklets were completed by 328 MZ twin pairs aged 12-19 years, 6 months apart. Increased punitive discipline and negative life events were found to be relevant nonshared environmental factors that followed depression. Negative life events were the only factor that had a direct nonshared environmental association with concurrent depressive symptoms in adolescents independent of previous depressive symptoms, and all other study variables.

Common genetic vulnerability to depressive symptoms and coronary artery disease: a review and development of candidate genes related to inflammation and serotonin

OBJECTIVE

Although it is well established that depressive symptoms are associated with recurrent cardiac events among cardiac patients and novel cardiac events among participants with no known coronary artery disease (CAD), the nature of this association remains unclear. In this regard, little attention has been paid to the possibility that common genetic vulnerability contributes to both depressive symptoms and CAD. In this paper, we review the existing evidence for common genetic contributions to depression and CAD, primarily using evidence from twin and family studies, followed by a review of two major pathophysiological mechanisms thought to underlie covariation between depressive symptoms and CAD: inflammation and serotonin. We conclude with an overview of select candidate genes within these pathways.

METHODS

Literature review.

RESULTS

In twin studies, both depression and CAD appear heritable. In the only twin study to consider depression and CAD jointly, the correlation across heritabilities was 0.42, suggesting that nearly 20% of variability in depressive symptoms and CAD was attributable to common genetic factors. In addition, although it is plausible that genetic variation related to inflammation and serotonin may be associated with both depression and CAD, genetic variation related to inflammation has been primary examined in relation to CAD, whereas genetic variation in the serotonin system has been primarily examined in relation to depression.

CONCLUSIONS

It appears that the covariation of depressive symptoms and CAD may be attributable, in part, to a common genetic vulnerability. Although several pathways may be involved, genes within the inflammation and serotonin pathways may serve as good candidates for the first steps in identifying genetic variation important for depression, CAD or both.

Multivariate Genetic Analysis of Chronic Pelvic Pain and Associated Phenotypes

Chronic pelvic pain (CPP) is a common condition in women that is difficult to diagnose. Although heritability estimates have been published for some conditions potentially underlying pelvic pain, the heritability of CPP itself has never been investigated. Using data from 623 MZ and 377 DZ female twin pairs aged 29-50 from an Australian twin cohort, we found an increased CPP concordance among MZs compared to DZs, with tetrachoric correlations of 0.43 (95% CI: 0.26-0.58) and 0.11 (95% CI: -0.16-0.38), respectively. This corresponded to a heritability of 0.41 (95% CI: 0.25-0.56). Lack of correlations with environmental indicators suggested that violation of the equal environments assumption was not responsible for this effect. Multivariate Cholesky decomposition models incorporating CPP and significantly correlated phenotypes showed that the entire CPP heritability could be explained by genetic variance underlying endometriosis (38%), dysmenorrhoea (23%), fibroids (24%), and somatic distress (15%), the latter a possible indicator of increased nociception. CPP itself is unlikely to be a useful independent phenotype to conduct genetic aetiological studies; contributing conditions such as endometriosis and variation in nociception are likely to provide more useful phenotypes.

Heritability of individual depressive symptoms

BACKGROUND

In attempting to understand the familial basis of depression, most studies have focused on broad indices of depression and mood change. Broad indices may not adequately reflect the heritable basis of depression because of an unexplored possibility that not all symptoms are heritable.

METHODS

The heritability of individual depressive symptoms was estimated from a sample of 343 general population volunteer twin pairs who completed the Beck Depression Inventory, the Centre for Epidemiologic Studies Depression Scale and items from the Symptom Checklist assessing depressive symptoms. Principal component analysis of the items extracted 14 factors that represented a wide range of depressive symptomatology.

RESULTS

The factors were differentially heritable (h2 range: 0.0-35.0%). The factors that have a heritable basis described endogenous or physiological functions (e.g. loss of appetite, libido/pleasure). Symptoms such as negative affect or tearfulness did not have a heritable basis, suggesting that these symptoms are responses to negative life events/experiences or a learned association to changes in physiologic function.

LIMITATIONS

Relatively small size of the sample.

CONCLUSIONS

Depressive symptoms are differentially heritable and the results suggest that future research, such as genotyping studies, separates heritable and non-heritable symptom clusters prior to analysis. This will help identify which genes are involved and what their function in depression may be, leading to the development of more targeted and effective therapies.

Depressive symptoms and metabolic risk in adult male twins enrolled in the National Heart, Lung, and Blood Institute twin study

OBJECTIVE

To determine the extent to which depressive symptoms are associated with metabolic risk factors and whether genetic or environmental factors account for this association.

METHOD

Twin structural equation modeling was employed to estimate genetic and environmental contributions to the covariation of depressive symptoms, as indexed by the Centers for Epidemiological Studies-Depression Scale, and common variance among blood pressure, body mass index, waist-to-hip ratio, and serum triglycerides and glucose among 87 monozygotic and 86 dizygotic male twin pairs who participated in the NHLBI twin study.

RESULTS

Depressive symptoms were associated with individual components of the metabolic syndrome and common variance among the risk factors. Twin structural equation modeling indicated that the associations were attributable to environmental (nongenetic) factors.

CONCLUSIONS

These results support the hypothesis that depressive symptoms may increase risk for a pattern of physiological risk consistent with the metabolic syndrome.

Covariation of psychosocial characteristics associated with cardiovascular disease: genetic and environmental influences

OBJECTIVE

Three psychosocial characteristics associated with cardiovascular disease (CVD)-depression, hostility, and social support-tend to correlate with one another. However, the causes of each characteristic and why they tend to co-occur are not completely understood. Therefore, the current study used a twin design to examine the relative contributions of genetic and environmental influences to the variation and covariation of these three psychosocial characteristics.

METHODS

The sources of variation and covariation among the Beck Depression Inventory, the Cook-Medley Hostility Scale, and the Interpersonal Support Evaluation List were examined in a young adult community sample of 157 monozygotic and 75 dizygotic twin pairs.

RESULTS

Phenotypic confirmatory factor analysis indicated that a single latent factor could account for their moderate intercorrelations. Twin analyses indicated that the Beck Depression Inventory and Interpersonal Support Evaluation List were each influenced by genetic and nonshared environmental factors, whereas the Cook-Medley Hostility Scale was influenced by familial (genetic and/or shared environmental) and nonshared environmental factors. Bivariate associations between these scales were largely determined by common genetic effects and, to a lesser degree, common nonshared environmental effects. Covariation among the three scales could be explained by a single common genetic factor and a common nonshared environmental factor. Environmental factors shared within families did not contribute to covariation among the psychosocial characteristics.

CONCLUSIONS

The results challenge the conventional approach of examining these psychosocial variables as independent risk factors for cardiovascular disease and argue for the importance of investigating specific causes for their covariation.

Genetic probes of three theories of maternal adjustment: I. Recent evidence and a model

Studies focusing on genetic and social influences on maternal adjustment will illumine mother's marriage, parenting, and the development of psychopathology in her children. Recent behavioral genetic research suggests mechanisms by which genetic and social influences determine psychological development and adjustment. First, heritable, personal attributes may influence individuals' relationships with their family members. These genetically influenced family patterns may amplify the effects of adverse, heritable personal attributes on adjustment. Second, influences unique to siblings may be the most important environmental determinants of adjustment. We derive three hypotheses on maternal adjustment from integrating these findings from genetic studies with other contemporary research on maternal adjustment. First, mother's marriage mediates the influence of her heritable, personal attributes on her adjustment. Second, mother's recall of how she was parented is partially genetically influenced, and both her relationships with her spouse and her child mediate the impact of these genetically influenced representations on her current adjustment. Third, characteristics of mother's spouse are important influences on difference between her adjustment and that of her sister's. These sibling-specific influences are unrelated to mother's heritable attributes. The current article develops this model, and [figure: see text] the companion article describes the Twin Mom Study that was designed to test it as well, as its first findings. Data from this study can illumine the role of family process in the expression of genetic influence and lead to specific family interventions designed to offset adverse genetic influences.

The genetic epidemiology of self-esteem

BACKGROUND

Previous studies on self-esteem have focused exclusively on its psychosocial determinants. The goal of the present study is to clarify genetic v. environmental determinants of self-esteem.

METHOD

Participants were Caucasian women sampled from the Virginia Twin Register: 363 pairs of MZ and 238 pairs of DZ twins were available from the first wave of the study, and 430 pairs of MZ and 308 pairs of DZ twins from the second. Self-esteem was assessed with the Rosenberg's Self-Esteem Scale.

RESULTS

Using univariate twin analyses of self-esteem and a repeated measurement twin model, we found that self-esteem is a moderately heritable trait (heritability = 52% in the repeated measurement model); environmental influences are also very important, and are probably mostly not shared by members of a twin pair.

CONCLUSIONS

Aetiological models of self-esteem which examine only psychosocial factors are incomplete; genetic factors need to be integrated.

Sex-specific causal factors and effects of common environment for symptoms of anxiety and depression in twins

Two thousand five hundred seventy intact pairs and 724 single responders from Norwegian twins aged 18-25 years completed questionnaires with information about anxiety and depression and perceived cotwin closeness. The aim of the study was the univariate estimation of sex-specific genetic and environmental effects on an index tapping symptoms of anxiety and depression. An index of social closeness between cotwins was significantly related to the cotwin correlation for anxiety/depression scores. MZ pairs were reported to be closer than DZ pairs, and like-sexed DZ pairs were closer than unlike-sexed pairs. The symptom data were adjusted for this apparent violation of the "equal-environment" assumption in twin studies, but the adjustment did not dramatically affect the parameter estimates of genetic and environmental effects on anxiety/depression. A model specifying male (aM) and female (aF) genetic additive effects, shared environment for males (cM), and individual environmental effects (eM and eF) fitted the adjusted data very well. An alternative model, specifying aM = aF, cM = cF, and eM = eF, and no correlation between those environmental factors shared by brothers and those shared by sisters, fitted equally well. Estimated proportions of total variance from the first model were aM2 = .30, aF2 = .52, and cM2 = .21. The estimates from the second model were aM2 = aF2 = .43 and cM2 = cF2 = .11.

Childhood Experience of Care and Abuse (CECA): a retrospective interview measure

The development of a retrospective, investigator-based interview measure of Childhood Experience of Care and Abuse (CECA) used with two community samples of adults in London is described. The component ratings are shown to have satisfactory inter-rater reliability and also validity as determined by agreement between sisters' independent accounts. The association between the different childhood scales is explored as well as the relationship of childhood experiences to adult depression. Methodological issues concerning investigator-based versus respondent-based measures of childhood are discussed and a case made for use of the former. Advantages of using the CECA, a retrospective, time-based measure of childhood, are outlined.

Low genetic effect and age-specific family effect for symptoms of anxiety and depression in nuclear families, halfsibs and twins

Questionnaire information on symptoms of anxiety/depression was obtained from 61,286 persons, most of whom could be grouped in families as spouses, parents, offspring, siblings, halfsibs and twins. The correlations between mental health in relatives, varying somewhat by sex, were: 0.27 for 18,768 pairs of spouses, 0.12 to 0.17 for 30,888 pairs of parents and offspring, 0.11 to 0.18 for 13,134 pairs of siblings, 0.27 to 0.35 for 57 pairs of MS twins, -0.06 to 0.10 for 60 pairs of DZ twins, 0.30 for 88 pairs of halfsibs reared together, and 0.16 for 40 pairs of halfsibs reared apart. The heritability was estimated to be between 0 and 0.20. There was a significant effect of environmental transmission from mother, but not from father, to offspring. The effect of environmental factors shared by sisters was substantial, the corresponding effect was lower in brothers, and zero in siblings of opposite sex. The correlations decreased with increasing age differences between relatives, implying effects of age-specific genes or environmental factors in the family.