An Update of Twin Research in Spain: The Murcia Twin Registry.

The Murcia Twin Registry (MTR) is the only population-based registry in Spain. Created in 2006, the registry has been growing more than a decade to become one of the references for twin research in the Mediterranean region. The MTR database currently comprises 3545 adult participants born between 1940 and 1977. It also holds a recently launched satellite registry of university students (N = 204). Along five waves of data collection, the registry has gathered questionnaire and anthropometric data, as well as biological samples. The MTR keeps its main research focus on health and health-related behaviors from a public health perspective. This includes lifestyle, health promotion, quality of life or environmental conditions. Future short-term development points to the expansion of the biobank and the continuation of the collection of longitudinal data.

Validation of the Chinese version of Community Assessment of Psychic Experiences (CAPE) in an adolescent general population.

The Community Assessment of Psychic Experiences (CAPE) is a popular 42-item self-report assessment of psychosis proneness (PP) that has been widely-translated. However, there is as yet no validation of CAPE in non-Western languages. Here, we validated a Chinese translation of CAPE ("CAPE-C") in a young Chinese community sample. Factor analyses were employed in a sample of 660 individuals (mean age=18.63) to identify a culturally-sensitive factor structure for CAPE-C (Study 1). Since confirmatory factor analysis (CFA) suggested that CAPE-C did not follow the original factor structure, exploratory factor analysis and follow-up CFA were employed to establish an alternative structure, resulting in a 15-item "CAPE-C15" which retained a three-factor structure tapping positive, negative and depressive symptoms. To demonstrate the specificity of CAPE-C15 as a measure of PP, we conducted regression analyses to examine associations between CAPE-C15 dimensions and other measures of psychotic and depressive symptoms (Study 2). Results confirmed that CAPE-C15 dimensions showed specific associations with relevant symptom dimensions of other measures, but not with irrelevant ones. Finally, to aid interpretation of CAPE-C15 scores, Receiver Operating Characteristic analysis was conducted to establish a cut-off score that could indicate test-takers' need for clinical attention (Study 3). We found that a cut-off score of 8.18 on CAPE-C15 positive and negative symptom frequency and distress scores distinguished individuals whose PP was within normal ranges from those at psychometric high-risk (sensitivity: 78.6%; specificity: 77.7%). CAPE-C15 will likely prove relevant to researchers and healthcare providers who serve Chinese-speaking adolescents and young adults.

The association of PTSD with physical and mental health functioning and disability (VA Cooperative Study #569: the course and consequences of posttraumatic stress disorder in Vietnam-era veteran twins).

PURPOSE: To assess the relationship of posttraumatic stress disorder (PTSD) with health functioning and disability in Vietnam-era Veterans. METHODS: A cross-sectional study of functioning and disability in male Vietnam-era Veteran twins. PTSD was measured by the Composite International Diagnostic Interview; health functioning and disability were assessed using the Veterans RAND 36-Item Health Survey (VR-36) and the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0). All data collection took place between 2010 and 2012. RESULTS: Average age of the 5,574 participating Veterans (2,102 Vietnam theater and 3,472 non-theater) was 61.0 years. Veterans with PTSD had poorer health functioning across all domains of VR-36 and increased disability for all subscales of WHODAS 2.0 (all p < .001) compared with Veterans without PTSD. Veterans with PTSD were in poorer overall health on the VR-36 physical composite summary (PCS) (effect size = 0.31 in theater and 0.47 in non-theater Veterans; p < .001 for both) and mental composite summary (MCS) (effect size = 0.99 in theater and 0.78 in non-theater Veterans; p < .001 for both) and had increased disability on the WHODAS 2.0 summary score (effect size = 1.02 in theater and 0.96 in non-theater Veterans; p < .001 for both). Combat exposure, independent of PTSD status, was associated with lower PCS and MCS scores and increased disability (all p < .05, for trend). Within-pair analyses in twins discordant for PTSD produced consistent findings. CONCLUSIONS: Vietnam-era Veterans with PTSD have diminished functioning and increased disability. The poor functional status of aging combat-exposed Veterans is of particular concern.

Quantitative genetic research on sleep: a review of normal sleep, sleep disturbances and associated emotional, behavioural, and health-related difficulties.

Over the past 50 years, well over 100 twin studies have focussed on understanding factors contributing to variability in normal sleep-wake characteristics and sleep disturbances. Whilst we have gained a great deal from these studies, there is still much to be learnt. Twin studies can be used in multiple ways to answer questions beyond simply estimating heritability. This paper provides a comprehensive review of some of the most important findings from twin studies relating to sleep to date, with a focus on studies investigating genetic and environmental influences contributing to i) objective and subjective measures of normal sleep characteristics (e.g., sleep stage organisation, sleep quality); as well as sleep disturbances and disorders such as dyssomnias (e.g., insomnia, narcolepsy) and parasomnias (e.g., sleepwalking, bruxism); ii) the persistence of sleep problems from childhood to adulthood, and the possibility that the aetiological influences on sleep change with age; iii) the associations between sleep disturbances, emotional, behavioural and health-related problems; and iv) processes of gene-environment correlation and interaction. We highlight avenues for further research, emphasising the need to further consider the aetiology of longitudinal associations between sleep disturbances and psychopathology; the genetic and environmental overlap between sleep and numerous phenotypes; and processes of gene-environment interplay and epigenetics.

A comparison of the construct validity of two alternative approaches to the assessment of psychopathy in the community.

This study compared the validity of 2 different self-report approaches to the assessment of psychopathy in nonforensic samples: the Psychopathy Resemblance Index (PRI), derived from a measure of normal personality functioning, and the Self-Report Psychopathy Scale (SRP), developed specifically to assess the maladaptive traits associated with psychopathy. In 2 adult samples (n (1) = 260, n(2) = 250), the PRI and the SRP were positively correlated with each other and with measures of maladaptive personality traits related to Machiavellianism and narcissism. However, unlike the SRP, the PRI was independent of trait empathy and general psychopathology and was positively associated with trait emotional intelligence. These results suggest that the PRI captures a more adaptive variant of psychopathy than does the SRP.

A time-lagged momentary assessment study on daily life physical activity and affect.

OBJECTIVE: Novel study designs using within-subject methodology and frequent and prospective measurements are required to unravel direction of causality and dynamic processes of behavior over time. The current study examined the effects of physical activity on affective state. A primary and within-study replication sample was derived from twin pairs. METHODS: Female twins (n = 504) participated in an experience sampling method study at baseline. Positive and negative affective changes were examined before and following daily life increases in physical activity. Neuroticism was measured at baseline and depressive symptoms were assessed at baseline and at each of four follow-up assessments. Diagnoses, derived by Structured Clinical Interview for Diagnostic and Statistical Manual for Mental Health-IV axis I disorders, (A. P. A., 1994) were obtained at baseline. RESULTS: A significant increase in positive affect (PA) following the moment of increase in physical activity was replicated across both samples up to 180 min after physical activity. There was no effect of physical activity on negative affect (NA). Across the two samples, a history of fulfilling diagnostic criteria for depression at least once moderated the effect of physical activity on PA, in that the effect was lost more rapidly. CONCLUSIONS: The study supports a causal effect of physical activity on PA. However, people with past experience of clinical depression may benefit less from the PA-inducing effect of physical activity. These findings have implications for the use of physical exercise in clinical practice.

Gene-environment processes linking aggression, peer victimization, and the teacher-child relationship.

Aggressive behavior in middle childhood is at least partly explained by genetic factors. Nevertheless, estimations of simple effects ignore possible gene-environment interactions (G × E) or gene-environment correlations (rGE) in the etiology of aggression. The present study aimed to simultaneously test for G × E and rGE processes between aggression, on the one hand, and peer victimization and the teacher-child relationship in school, on the other hand. The sample comprised 124 MZ pairs and 93 DZ pairs assessed in Grade 1 (mean age = 84.7 months). Consistent with rGE, children with a presumed genetic disposition for aggression were at an increased risk of peer victimization, whereas in line with G × E, a positive relationship with the teacher mitigated the genetically mediated expression of aggression.

Multidimensional assessment of health status in a dependent sample: an exploratory analysis for adult twins in China.

Health is a multidimensional and continual concept. Traditional latent analytic approaches have inherent deficits in capturing the complex nature of the concept; however, the Grade of Membership (GoM) model is well suited for this problem. We applied the GoM method to a set of 31 indicators to construct ideal profiles of health status based on physical, mental and social support items among 848 adult twins from Qingdao, China. Four profiles were identified: healthy individuals (pure type I), individuals with personality disorders (pure type II), individuals with mental impairments (pure type III) and individuals with physical impairments (pure type IV). The most frequently occurring combination in this population was profiles I, II, IV (14.74%), followed by profiles I, II, III, IV (13.44%), and then type I (11.08%). Only 13.56% of subjects fell completely into one single pure type, most individuals exhibited some of the characteristics of two or more pure types. Our results indicated that, compared to conventional statistical methods, the GoM model was more suited to capture the complex concept of health, reflecting its multidimensionality and continuity, while also exhibiting preferable reliability. This study also made an important contribution to research on GoM application in non-independent samples.

Unveiling patterns of affective responses in daily life may improve outcome prediction in depression: a momentary assessment study.

OBJECTIVE: Daily life affective responses are closely linked to vulnerability and resilience in depression. Prediction of future clinical course may be improved if information on daily life emotional response patterns is taken into account. METHOD: Female subjects with a history of major depression (n=83), recruited from a population twin register, participated in a longitudinal study using momentary assessment technology with 4 follow-up measurements. The effect of baseline daily life emotional response patterns (affect variability, stress-sensitivity and reward experience) on follow-up depressive symptomatology was examined. RESULTS: Both reward experience (B=-0.30, p=0.001) and negative affect variability (B=0.46, p=0.001) predicted future negative affective symptoms independent of all other dynamic emotional patterns and conventional predictors. CONCLUSION: Daily life information on dynamic emotional patterns adds to the prediction of future clinical course, independent of severity of symptoms and neuroticism score. Better prediction of course may improve decision-making regarding quantitative and qualitative aspects of treatment.

Brief Report: Interaction between social class and risky decision-making in children with psychopathic tendencies.

OBJECTIVE: Adult psychopaths are thought to have risky decision-making and behavioral disinhibition, but little is known about the moderating effects of psychosocial factors and whether these associations can be observed in children with psychopathic tendencies. This study tests the biosocial hypothesis that social class will moderate psychopathy-neurocognition relationships, with these effects being stronger in children from high social classes. METHOD: Preadolescent community twins (N=298) were assessed on decision-making (Iowa Gambling) and behavior inhibition (Porteus Maze) tasks, while psychopathic tendencies and socioeconomic status were assessed by the child's caregiver. RESULTS: A significant interaction was observed whereby risky decision-making was associated with psychopathic tendencies only in children from benign home environments. CONCLUSIONS: Findings support a biosocial interaction perspective on child psychopathy, suggesting that risky decision-making may particularly predispose to psychopathic traits in children from benign home backgrounds.

Socioeconomic status and social support following illicit drug use: causal pathways or common liability?

The negative social attributes associated with drug use and abuse/dependence may arise as a result of shared genetic or environmental factors rather than through causal pathways. To evaluate this possibility, structured interviews were conducted for 3969 male and female twins from the Mid-Atlantic Twin Registry and evaluations of their socioeconomic status (SES), social interactions, and use of drugs were obtained. Drug involvement was categorized as never used, tried, or met criteria for abuse or dependence. A co-twin control design was implemented using hierarchical linear modeling to assess whether twins who used drugs experienced lower SES and social support than non-using co-twins. Poorer social functioning in the drug-exposed twin is consistent with a causal relationship, while similar functioning in the drug exposed versus naive twins imply shared genetic or common environmental factors. Use of drugs was not significantly related to any SES measures. However, education and job status appear to share genetic influences with drug abuse/dependence. Lower income was not related to abuse/dependence of drugs. Negative interactions with friends and relatives share genetic factors with use of drugs, but the escalation from trying drugs to abusing them appears to generate discord between the abuser and friends and relatives in a causal fashion. These results indicate that presumptive causal influences of drug abuse/dependence on low SES may actually be mediated by shared genes. Drug use and social discord also appear to have shared genetic factors, but increased levels of drug involvement seem to causally influence social interactions.

Genetic and environmental influences on socio-emotional behavior in toddlers: an initial twin study of the infant-toddler social and emotional assessment.

BACKGROUND: Relatively little is known about the genetic architecture of childhood behavioral disorders in very young children. METHOD: In this study, parents completed the Infant-Toddler Social and Emotional Assessment, a questionnaire that assesses symptoms of childhood disorders, as well as socio-emotional competencies, for 822 twin pairs (49.3% female; age 17-48 months) participating in the Wisconsin Twin Project. Psychometric, rater bias, and sex-limitation models explored the role of genetic and environmental influences on (1) externalizing and internalizing behavior; (2) less commonly assessed behaviors pertaining to physical and emotional dysregulation, general competencies, social relatedness; and (3) infrequent behaviors such as those associated with pervasive developmental delays. RESULTS: Heritable influences accounted for the majority (56% or more) of variation in behavior that was commonly observed by both parents. The remaining variance was associated with non-shared environmental factors, with the exception of competency and atypical behavior, which were also influenced by shared environmental factors. In contrast, for most behaviors, the variation unique to mother and father ratings was split between variation due to shared environment or rater biases and to measurement error. Little evidence emerged for sex differences in the underlying causes of variation.

[Paranoid schizophrenia in monozygotic twins--from caregiver to patient affected]. / Paranoide Schizophrenie bei eineiigen Zwillingen--vom Angehörigen zum Betroffenen.

OBJECTIVE: The aim of this case study is to show how a monozygotic twin perceives the schizophrenic disorder of his twin brother and how these experiences affect his own handling and coping after the beginning of his own schizophrenic disorder. PATIENT: A 46-year-old patient with a first episode of schizophrenia who took care of his twin brother with a disease history of 25 years of schizophrenia. RESULTS: In this case the little knowledge the patient had of his schizophrenic disorder and his lasting lack accessing his illness in the context of a defensive mechanism were striking. Concurrently, the patient overestimated his loading capacity. CONCLUSIONS: A long time of caregiving of a schizophrenic twin brother does not necessarily facilitate the coping with a schizophrenic illness of one's own. Defensive mechanisms could inhibit the implementation of constructive coping strategies with the illness.

Is the association between posttraumatic stress disorder symptoms and poor health due to a common familial or genetic factor?

OBJECTIVE: The objective of this study was to identify genetic, familial and environmental contributions to the association between posttraumatic stress disorder (PTSD) symptoms and poor health. METHODS: A community sample of 1852 twin pairs was assessed for symptoms of PTSD [with the Impact of Events Scale (IES)] and self-reported global health status using a single five-level question. An ordinal logistic regression model estimated odds ratio/s (OR) for the association between PTSD and health status. Within-pair analysis assessed confounding by familial and genetic factors and adjusted for the possible confounding influence of age, sex, race, education and self-reported physician diagnosis of depression. RESULTS: The IES was strongly and significantly associated with self-reported health [OR=1.8; 95% confidence interval (95% CI)=1.5-2.2; highest quartile vs. lowest quartile]. This association remained significant in within-pair analysis (OR=1.3; 95% CI=1.0-1.7), but after further adjustment for sociodemographics and depression, it was no longer significant (P(trend)=.17). Separate analysis by zygosity did not show differential effect in monozygotic or dizygotic pairs. CONCLUSION: These findings suggest that the association between PTSD symptoms and poor health is, in part, due to familial confounding and sociodemographic factors. Little evidence of confounding by genetic factors was found. These findings suggest that early prevention efforts would have the greatest potential for improving poor health in PTSD-prone patients, whereas later intervention efforts directed at treating PTSD may have a more limited impact on improving poor health.

A twin study of the association of post-traumatic stress disorder and combat exposure with long-term socioeconomic status in Vietnam veterans.

This study examines the association between post-traumatic stress disorder (PTSD) and combat exposure with the socioeconomic status of 2210 male monozygotic veteran twin pairs in 1987. In the unadjusted analysis on individuals, modest correlations indicated that those with PTSD were more likely to have been divorced, and less likely to be currently employed or to achieve high status in income, education or occupation. In the crude analysis of veterans not suffering from PTSD, there were small positive correlations between combat level experienced and the likelihood of ever being married, ever being divorced, and the number of years employed at the current job. However, when we examined identical twins discordant for PTSD, and adjusted for pre-military and military service factors, only unemployment remained significant. Likewise, in combat-discordant twins, no significant effects on the socioeconomic indicators were seen. We conclude that PTSD and combat experience in Southeast Asia have not had a major impact on the socioeconomic status of veterans.

Ecocultural assessment in families of children with developmental delays: construct and concurrent validities.

Home interviews were conducted with 102 families of children with developmental delays to assess ecocultural family resources and constraints, values, and goals as well as proactive adaptive efforts to deal with their circumstances. Interview topics included (a) economic factors; (b) child safety, health, and education; (c) domestic and childcare workloads; (d) familial support networks; and (e) sociocultural influences. Factor analyses performed on the ecocultural measures revealed 12 salient factors. Results indicated that some of the ecocultural factors were unique and statistically independent of the traditional measures of home environment (e.g., child-rearing attitudes, cognitive stimulation of the child, and general psychosocial climate). Significant relations were found between certain ecocultural factors and child's developmental status. Both ecocultural factors and traditional family measures accounted for significant variation in child outcomes.

Investigation of the reliability and factor structure of a questionnaire for assessment of the premenstrual syndrome.

Data are presented from 696 women who completed a 35-item retrospective self-report PMS questionnaire. Item analysis resulted in the elimination of six items which predominantly reflected physical symptomatology. The resultant (29-item) questionnaire demonstrated a coefficient alpha value of 0.94 corresponding to a very high level of internal consistency and split-half reliability. It is argued that discrepancies in previous PMS research based on questionnaire data may, in part, be due to inadequate attention being devoted to achieving homogeneity of the PMS construct. A high level of internal consistency is a necessary condition for global PMS scores to be meaningful. Factor analysis of the revised questionnaire resulted in a two factor model corresponding to 'dysphoria' and 'dysfunction'. This leads to a simple four quadrant typology of PMS which may further understanding of this 'purer' PMS construct.

Intoxication after an acute dose of alcohol: an assessment of its association with alcohol consumption patterns by using twin data.

We examined the hypothesis that genetically determined differences in sensitivity to alcohol explain some of the genetic variation in alcohol consumption pattern. Self-report data on average weekly alcohol consumption and self-ratings of intoxication after a standard dose of ethanol (0.75 g/kg body weight), used as an index of sensitivity, were obtained on 206 Australian twin pairs. Significant genetic covariance between weekly consumption and level of intoxication after alcohol intake was found in males, lower ratings of intoxication being associated with increased consumption. However, when direction of causation models were fitted to the male twin data, the hypothesis that decreased sensitivity was a cause of increased consumption was rejected. The major causal effect was that of weekly consumption on level of sensitivity. A similar, although nonsignificant, trend was observed in females. The strength of the association between self-report of average weekly consumption and level of intoxication after a standard dose of alcohol supports the validity of the former measure.