Health locus of control in late life: a study of genetic and environmental influences in twins aged 80 years and older.

The factor structure of health locus of control (Form A; K. A. Wallston, B. S. Wallston, & R. DeVellis, 1978) was examined in 420 octogenarians (M age = 83.2 years), and the contributions of genetic and environmental factors to health-control beliefs in 141 octogenarian twin pairs (71 identical, 70 same-sex fraternal) were estimated. Factor analyses reproduced previously proposed factors (Internal, Chance, and Powerful Others). Associations between health-control beliefs and life satisfaction, depression, and other health-related measures (e.g., self-rated health, outpatient contacts, and hospitalization), were modest. Quantitative genetic analyses revealed significant shared environmental influence on the Chance subscale, and significant familiality (attributable to a combination of genetic and shared environmental influences) on the Powerful Others subscale; there was no evidence of familiality on the Internal subscale.     

Genetic and environmental influences on interpersonal cognitions and associations with depressive symptoms in 8-year-old twins

Less is known about depression in children than in adults. This study integrates fields by combining cognitive and interpersonal research investigating childhood depression symptoms through the use of a genetic framework. Three research questions are addressed. First, what are the associations among interpersonal cognitions, anxiety, and depression? Second, what are the relative magnitudes of genetic and environmental influences on interpersonal cognitions? Third, to what extent do genetic and environmental influences explain associations between interpersonal cognitions and depression? Three hundred pairs of 8-year-old twins reported on symptoms of depression and anxiety by completing the Children's Depression Inventory and the Screen for Childhood Anxiety-Related Emotional Disorders. The authors examined interpersonal cognitions with the Children's Expectation of Social Behaviors and the Perceptions of Peers and Self Questionnaires. Interpersonal cognitions were more strongly correlated with depression (mean r = .35) than with anxiety (mean r = .13). Genetic influence on interpersonal cognitions was small (M = 3%), and associations between interpersonal cognitions and depression were mainly explained by environmental influences. These latter findings may result from interpersonal cognitions in young children, reflecting life experiences as opposed to trait-like cognitive biases.     

Nonshared environmental influences and personality differences in adult twins

The twin design was used to examine the importance of different experiences of siblings within the family and to identify relations between twins' personality differences and their differential experiences. A sample of 161 monozygotic and 74 dizygotic twin individuals between the ages of 18 and 75 years retrospectively reported on their different experiences when growing up. The Sibling Inventory of Differential Experience (SIDE) was used for the first time with a sample of twin siblings. In addition, the twins provided self-report measures of affect and personality. In contrast to results from a sibling adoption design, this study of twins showed greater evidence for genetic variance in the SIDE scales. Nevertheless, the SIDE showed significant associations with differences in personality and affect for monozygotic twins, which reflect pure environment-behavior relations.     

Age differences in genetic and environmental influences on eating attitudes and behaviors in preadolescent and adolescent female twins

A sample of 680 11- and 602 17-year-old female twins was used to examine (a) age differences in genetic and environmental influences on disordered eating attitudes and behaviors and (b) associations between body mass index (BMI) and eating attitudes and behaviors. Univariate, biometrical model-fitting analyses indicated that 11-year-old twins exhibited less genetic and greater shared environmental influence on eating attitudes and behaviors than 17-year-old twins. Bivariate model-fitting analyses indicated that the relationship between BMI and eating attitudes was mediated primarily by common shared environmental influences in 11-year-old twins and common genetic influences in 17-year-old twins. Nonetheless, the majority of genetic influences on eating attitudes and behaviors in older twins were due to genetic effects that are independent of those operating in BMI.     

Genetic and environmental influences on aggression in 4- to 7-year-old twins

Aggressive behaviors of 38 twin pairs (21 monozygotic [MZ], 17 dizygotic [DZ]) between the ages of 4 and 7 years were assessed through mothers' ratings and observations in their homes. An observation checklist was developed in which mothers were asked to observe and report each child's specific aggressive behaviors for a total of 6 hours spread over 3 days. In particular the observations focused on the following behaviors: rejection, destructiveness, negativism, noncompliance, teasing, physical negative, insult, verbal threat, and yelling. Biometrical genetic analysis evidenced significant heritable influences on composite aggression scores in both the observation checklist and the mothers' ratings; heritability estimates varied from.24 to.94 depending on the aggression nieasnre used, with scores from the mothers' observations demonstrating smaller genetic effect than those of the parental ratings of the environmental sources of variance, within-family factors were far more important than the between-family ones. The results also yielded significant sex and zygosity differences for means of some of the specific aggressive behaviors, where males and DZ twins scored higher than females and MZ twins. It was suggested that future studies should include more detailed investigations of the context in which specific aggressive behaviors occur and the sources toward which they are directed in order to determine the extent to which different types of aggression may have different etiologies.     

The shared and unique genetic relationship between mental well-being,depression and anxiety symptoms and cognitive function in healthy twins

Alterations to cognitive function are often reported with depression and anxiety symptoms, yet few studies have examined the same associations with mental well-being. This study examined the association between mental well-being, depression and anxiety symptoms and cognitive function in 1502 healthy adult monozygotic (MZ) and dizygotic (DZ) twins, and the shared/unique contribution of genetic (G) and environmental (E) variance. Using linear mixed models, mental well-being was positively associated (p?β?=?0.127), inhibition (β?=?0.096), cognitive flexibility (β?=?0.149), motor coordination (β?=?0.114) and working memory (β?=?0.156), whereas depression and anxiety symptoms were associated (p?β?=??0.134), inhibition (β?=??0.139), cognitive flexibility (β?=??0.116) and executive function (β?=??0.139). Bivariate twin modelling showed well-being shared a small environmental correlation with motor coordination and a small genetic correlation with working memory. Trivariate twin modelling showed well-being shared a small genetic correlation with inhibition, whereas depression and anxiety symptoms shared a small environmental correlation with inhibition. The remaining variance was mostly driven by unique G and/or E variance. Overall, well-being and depression and anxiety symptoms show both independent and shared relationships with cognitive functions but this is largely attributable to unique G or E variance and small shared G/E variance between pairs of variables.     

Longitudinal relationships between depressive symptoms and health in normal older and middle-aged adults

Comorbidity between health and depression is salient in late life, when risk for physical illness rises. Other community studies have not distinguished between the effects of brief and long-standing depressive symptoms on excess morbidity and mortality. S. Cohen and M. S. Rodriguez's (1995) differential hypothesis of pathways between depression and health was used to examine the relationships between health and depression in a prospective probability sample of 1,479 community-resident middle-aged and older adults. Findings suggest that different durations of depressive symptoms have different relationships to health. Health had an impact on short-term increases in depressive symptoms but depressive symptoms had a weaker impact on health. The reciprocal impact was indistinguishable from the health influence on depression. In contrast, longer term depressive symptoms had a clear impact on health. The results imply that physical illness can affect depressive states; depressive traits but not states can affect illness.     

Physician-diagnosed medical disorders in relation to PTSD symptoms in older male military veterans.

The association between physician-diagnosed medical disorders and combat-related posttraumatic stress disorder (PTSD) symptoms was examined in 605 male combat veterans of World War II and the Korean conflict. Physician exams were performed at periodic intervals beginning in the 1960s. PTSD symptoms were assessed in 1990. Cox regression was used to examine the onset of each of 12 disorder categories as a function of PTSD symptoms, controlling for age, smoking, alcohol use, and body weight at study entry. Even with control for these factors, PTSD symptoms were associated with increased onset of arterial, lower gastrointestinal, dermatologic, and musculoskeletal disorders. There was only weak evidence that PTSD mediated the effects of combat exposure on morbidity. Possible mediators of the relationship between combat exposure, PTSD, and physical morbidity are discussed.     

Genetic and environmental influences on rumination and its covariation with depression

This study examined the extent to which rumination and depression share genetic and environmental influences in a community sample of adult twins (N = 663). Twins completed multiple rumination questionnaires, a depressive symptoms questionnaire and a diagnostic interview. Rumination was moderately heritable (h² = .37–.41 for the latent variable) and substantially influenced by nonshared environmental factors, and these results were consistent across different measures. Nonshared environmental influences on rumination were larger for women than men. Depressive symptoms and diagnosis were influenced by genetic and nonshared environmental factors (h² = .30–.45). The genetic correlations between rumination and depression were moderate to large (rA = .40–.82), suggesting that a substantial proportion of the genetic influences on rumination overlap with those on depression. Results were similar when examining self-reported depressive symptoms and interview-based diagnosis of major depressive disorder. These results highlight the importance of rumination in the integration of cognitive and genetic models of depression risk.     

A study of genetic and environmental effects on the co-occurrence of problem behaviors in three-year-old twins

The authors examined the genetic and environmental causes of the co-occurrence of problem behaviors in children. The analyses involved mother and father ratings of Oppositional, Withdrawn/Depressed, Aggressive, Anxious, Overactive, and Sleep Problems in 446 monozygotic and 912 dizygotic pairs of 3-year-old twins. Genetic factors contributed on average .150 (37.3%), shared environment .206 (51.2%), and nonshared environment .046 (11.4%) to the phenotypic correlations between the syndromes. Genetic and environmental factors caused different groupings. Internalizing and Externalizing groupings were indicative of nonshared environmental factors; clusters of problem behaviors with either the Aggressive or Anxious symptoms were most suggestive of genetic factors, and high scores on all syndromes indicated shared environmental influences.     

Parental monitoring moderates the importance of genetic and environmental influences on adolescent smoking

Although there is a substantial literature on the role of parenting in adolescent substance use, most parenting effects have been small in magnitude and studied outside the context of genetically informative designs, raising debate and controversy about the influence that parents have on their children (D. C. Rowe, 1994). Using a genetically informative twin-family design, the authors studied the role of parental monitoring on adolescent smoking at age 14. Although monitoring had only small main effects, consistent with the literature, there were dramatic moderation effects associated with parental monitoring: At high levels of parental monitoring, environmental influences were predominant in the etiology of adolescent smoking, but at low levels of parental monitoring, genetic influences assumed far greater importance. These analyses demonstrate that the etiology of adolescent smoking varies dramatically as a function of parenting.     

Adolescent personality moderates genetic and environmental influences on relationships with parents

In contrast with early theories of socialization that emphasized the role of parents in shaping their children's personalities, recent empirical evidence suggests an evocative relationship between adolescent personality traits and the quality of the parent-adolescent relationship. Research using behavior genetic methods suggests that the association between personality and parenting is genetically mediated, such that the genetic effects on adolescent personality traits overlap with the genetic effects on parenting behavior. In the current study, the authors examined whether the etiology of this relationship might change depending on the adolescent's personality. Biometrical moderation models were used to test for gene- environment interaction and correlation between personality traits and measures of conflict, regard, and involvement with parents in a sample of 2,452 adolescents (M age = 17.79 years). They found significant moderation of both positive and negative qualities of the parent-adolescent relationship, such that the genetic and environmental variance in relationship quality varied as functions of the adolescent's levels of personality. These findings support the importance of adolescent personality in the development of the quality of the parent-adolescent relationship.     

Cognitive influences on perceived change in social support,motivation, and symptoms of depression

In settings ranging from informal conversation to medical interviews and surveys, people are often asked to judge changes in subjective states that are important to them, such as perceived social support, motivation to cope with a negative life event, and symptoms of depression. How accurate are such reports, and are there theories of cognitive processes that can predict the most likely types of misperception? To address these questions, self-report survey data were collected from 224 recently unemployed adults. The measures assessed current subjective states of self and social environment at two times, separated by 4 months. Among the results, persons with high self-esteem were particularly likely to underestimate changes for the worse between the two survey waves–evidence of an optimistic response bias. When the dimension being judged was unstable and ambiguous, people were more likely to overestimate improvement–evidence of an optimistic response style. The findings were evaluated in terms of alternate theories of cognitive bias and in terms of implications for subsequent studies and application.     

Early manifestations of childhood depression: influences of infant temperament and parental depressive symptoms

In this longitudinal study, 83 parents of infants between 3 and 12 months completed questionnaires assessing demographic information, infant temperament, and maternal depression. When these children were at least 18 months of age, parents completed follow‐up questionnaires assessing toddler temperament and depression‐like symptoms. We were primarily interested in the contributions of infant temperament and maternal depression to toddler depressive problems, and the analytic strategy involved controlling for toddler temperament in order to isolate the influence of infancy characteristics. The findings indicated that lower levels of infant regulatory capacity and greater severity of maternal depression were predictive of toddler depression‐like symptoms. Moderator effects of infant temperament were also examined, with the negative affectivity * maternal depression interaction emerging as significant. Follow‐up analyses indicated that the risk for early manifestations of depression was attenuated for children with lower negative affectivity in infancy and parents who reported lower levels of their own depressive symptoms; conversely, children exhibiting higher infant negative emotionality had higher levels of depression‐like symptoms as toddlers, regardless of their parents' level of depression. The present findings further suggest that parental depressive symptoms need not be ‘clinically significant’ to predict toddler affective problems. Copyright © 2008 John Wiley & Sons, Ltd.     

Sex differences in genetic and environmental influences on DSM-III-R attention-deficit/hyperactivity disorder

Approximately 5% of children are affected by attention-deficit/hyperactivity disorder (ADHD), and more boys are affected than girls. This study examined the magnitude of genetic and environmental influences on ADHD and several questions regarding sex differences in its prevalence and liability. The participants were 2,391 twin and sibling pairs from Australia, ages 3-18. ADHD symptoms in the general population were highly heritable (h2 = .85-.90), as were deviant ADHD scores in the selected population. The magnitude of familial influences was similar for boys and girls, although there were shared environmental influences on ADHD in girls but not boys and dominance genetic influences on ADHD in boys but not girls. Specific genetic and environmental influences were highly similar for boys and girls. Evidence supported the polygenic multiple threshold model rather than the constitutional variability model of sex differences in ADHD.     

Prosocial behavior from early to middle childhood: genetic and environmental influences on stability and change

Prosocial behavior is important for the functioning of society. This study investigates the extent to which environment shared by family members, nonshared environment, and genetics account for children's prosocial behavior. The prosocial behavior of twins (9,424 pairs) was rated by their parents at the ages of 2, 3, 4, and 7 and by their teachers at age 7. For parent ratings, shared environmental effects decreased from .47 on average at age 2 to .03 at age 7, and genetic effects increased from .32 on average to .61. The finding of weak shared environmental effects and large heritability at age 7 was largely confirmed through the use of teacher ratings. Using longitudinal genetic analyses, the authors conclude that genetic effects account for both change and continuity in prosocial behavior and nonshared environment contributes mainly to change.     

Importance of shared genes and shared environments for symptoms of depression in older adults.

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.     

Insomnia in relation to depression and somatic symptoms

A sample of 358 Kuwaiti volunteer college students responded to the Insomnia Scale, the Somatic Symptoms Inventory, and the Center for Epidemiologic Studies-Depression Scale. The only significant sex difference was in somatic symptoms on which women had a higher mean score than the men. Correlations between scores on the Insomnia Scale and both Depression scales were .51 and .54 and for Somatic Symptoms were .53 and .61 (p < .01) among men and women, respectively. The factor analysis of the intercorrelations yielded a highly loaded general factor for Psychological Disorder in both samples.     

Sex differences in the genetic and environmental influences on childhood conduct disorder and adult antisocial behavior

Sex differences in the genetic and environmental influences on childhood conduct disorder and adult antisocial behavior were examined in a large community sample of 6,383 adult male, female, and opposite-sex twins. Retrospective reports of childhood conduct disorder (prior to 18 years of age) were obtained when participants were approximately 30 years old, and lifetime reports of adult antisocial behavior (antisocial behavior after 17 years of age) were obtained 8 years later. Results revealed that either the genetic or the shared environmental factors influencing childhood conduct disorder differed for males and females (i.e., a qualitative sex difference), but by adulthood, these sex-specific influences on antisocial behavior were no longer apparent. Further, genetic and environmental influences accounted for proportionally the same amount of variance in antisocial behavior for males and females in childhood and adulthood (i.e., there were no quantitative sex differences). Additionally, the stability of antisocial behavior from childhood to adulthood was slightly greater for males than females. Though familial factors accounted for more of the stability of antisocial behavior for males than females, genetic factors accounted for the majority of the covariation between childhood conduct disorder and adult antisocial behavior for both sexes. The genetic influences on adult antisocial behavior overlapped completely with the genetic influences on childhood conduct disorder for both males and females. Implications for future twin and molecular genetic studies are discussed.