Genetic Correlates of Psychological Responses to the COVID-19 Crisis in Young Adult Twins in Great Britain

We investigated how the COVID-19 crisis and the extraordinary experience of lockdown affected young adults in England and Wales psychologically. One month after lockdown commenced (T2), we assessed 30 psychological and behavioural traits in more than 4000 twins in their mid-twenties and compared their responses to the same traits assessed in 2018 (T1). Mean changes from T1 to T2 were modest and inconsistent. Contrary to the hypothesis that major environmental changes related to COVID-19 would result in increased variance in psychological and behavioural traits, we found that the magnitude of individual differences did not change from T1 to T2. Twin analyses revealed that while genetic factors accounted for about half of the reliable variance at T1 and T2, they only accounted for ~ 15% of individual differences in change from T1 to T2, and that nonshared environmental factors played a major role in psychological and behavioural changes. Shared environmental influences had negligible impact on T1, T2 or T2 change. Genetic factors correlated on average .86 between T1 and T2 and accounted for over half of the phenotypic stability, as would be expected for a 2-year interval even without the major disruption of lockdown. We conclude that the first month of lockdown has not resulted in major psychological or attitudinal shifts in young adults, nor in major changes in the genetic and environmental origins of these traits. Genetic influences on the modest psychological and behavioural changes are likely to be the result of gene-environment correlation not interaction.

Are remitted affective disorders and familial risk of affective disorders associated with metabolic syndrome, inflammation and oxidative stress? - a monozygotic twin study

BACKGROUND

Metabolic syndrome (MetS) is associated with reduced life expectancy in patients with affective disorders, however, whether MetS also plays a role before the onset of affective disorder is unknown. We aimed to investigate whether MetS, inflammatory markers or oxidative stress act as risk factors for affective disorders, and whether MetS is associated with increased inflammation and oxidative stress.

METHODS

We conducted a high-risk study including 204 monozygotic (MZ) twins with unipolar or bipolar disorder in remission or partial remission (affected), their unaffected co-twins (high-risk) and twins with no personal or family history of affective disorder (low-risk). Metabolic Syndrome was ascertained according to the International Diabetes Federation (IDF) criteria. Inflammatory markers and markers of oxidative stress were analyzed from fasting blood and urine samples, respectively.

RESULTS

The affected and the high-risk group had a significantly higher prevalence of MetS compared to the low-risk group (20% v. 15% v. 2.5%, p = 0.0006), even after adjusting for sex, age, smoking and alcohol consumption. No differences in inflammatory and oxidative markers were seen between the three groups. Further, MetS was associated with alterations in inflammatory markers, and oxidative stress was modestly correlated with inflammation.

CONCLUSION

Metabolic syndrome is associated with low-grade inflammation and may act as a risk factor and a trait marker for affective disorders. If confirmed in longitudinal studies, this suggests the importance of early intervention and preventive approaches targeted towards unhealthy lifestyle factors that may contribute to later psychopathology.

Phenotypic and aetiological architecture of depressive symptoms in a Japanese twin sample

BACKGROUND

The phenotypic and aetiological architecture of depression symptomatology has been mostly studied in Western samples. In this study, we conducted a genetically informed factor analysis to elucidate both the phenotypic and aetiological architectures of self-reported depression among a Japanese adult twin sample.

METHODS

Depressive symptoms assessed by Zung's Self-rating Depression Scale were self-rated by 425 twin pairs (301 monozygotic and 124 dizygotic twin pairs) in a community sample in Japan.

RESULTS

An exploratory factor analysis extracted three symptom domains representing cognitive, affective and somatic symptomatology. A confirmatory factor analysis demonstrated that a bi-factor solution fitted better than the alternative solutions, implying that depression may be defined as a combination of a single general construct and three factors specific to each of the three symptom domains. A multivariate genetic analysis with the bi-factor solution showed that the general factor was substantially heritable (47%), and that only the affective symptom domain was significantly heritable (29%) among the three specific factors, their remaining variance being explained by non-shared environmental influences.

CONCLUSIONS

Depression symptomatology appears to be adequately captured by a substantially heritable general factor. The heritability of this factor (47%) in a Japanese adult sample is in line with commonly reported heritability estimates for depression. The three specific factors - cognitive, affective and somatic - are mostly explained by non-shared environmental factors, which include measurement error. The extent to which these specific factors are uniquely associated with correlates of depression when the general factor is accounted for should be investigated in future studies.

The association between general childhood psychopathology and adolescent suicide attempt and self-harm: A prospective, population-based twin study

Few quantitative behavior genetic studies have examined why psychopathology is associated with suicide attempt (SA) and self-harm (SH) in adolescence. The present study analyzed data from the Child and Adolescent Twin Study in Sweden to examine the extent to which genetic and environmental factors explain SA/SH and its association with psychopathology in childhood, an often-cited risk factor of subsequent SA/SH. When children were 9 or 12 years old (n = 30,444), parents completed the Autism-Tics, AD/HD and other Comorbidities Inventory (Larson et al., 2010) regarding their children's psychiatric problems as part of an ongoing, longitudinal study. At age 18 years (n = 10,269), adolescents completed self-report questionnaires, including SA/SH assessments. In a bifactor model of childhood psychopathology, a general factor of psychopathology was a statistically significant predictor of adolescent SA/SH at a higher magnitude (β, 0.25, 95% confidence interval [CI; 0.15, 0.34] for suicide attempt), as compared with specific factors of inattention, impulsivity, oppositional behavior, and anxiety/emotion symptoms. Quantitative genetic modeling indicated that the additive genetic influences on the general factor accounted for the association with each outcome (β, 0.24, 95% CI [0.13, 0.34] for suicide attempt). The results remained virtually identical when we fit a higher order factors model. Two additional outcomes demonstrated comparable results. The results extend current literature by revealing the shared genetic overlap between general psychopathology during childhood and adolescent SA/SH. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The relationship between independent and dependent life events and depression symptoms in Sri Lanka: a twin and singleton study

PURPOSE

Life events have been associated with a variety of mental health conditions including depression. There is a scarcity of research in South Asia exploring the aetiology of independent and dependent life events and their relationship with depression symptoms. This study aimed, in a Sri Lankan population, to identify the socio-demographic correlates and genetic and environmental influences on independent and dependent life events and their relationship with depression.

METHODS

Questionnaire data came from the Colombo Twin and Singleton Follow-up Study, CoTaSS-2 (N = 3969), a population study of Sri Lankan twins and singletons. Lifetime-ever independent and dependent life events were measured using a questionnaire and depressive symptoms using the Revised Beck's Depression Inventory. Structural Equation Model-fitting analyses explored the genetic and environmental influences on life events and depression.

RESULTS

Living in a rural environment and financial hardship were associated with greater reporting of independent and dependent life events. Sex differences were evident in the aetiology of life events and depression symptoms. Independent and dependent life events, but not depression symptoms, were heritable in males. Independent life events and depression symptoms, but not dependent life events, were heritable in females. Non-shared environmental influences explained phenotypic associations between independent life events and depression symptoms in both males and females. Genetic and non-shared environmental influences explained the phenotypic associations between dependent life events and depression symptoms in males. Only non-shared environment explained the covariation between dependent life events and depression symptoms in females.

CONCLUSIONS

Socio-demographic correlates of independent and dependent life events were similar to those reported in Western populations. Life events were associated with increased depression symptoms. Contrary to research in Western populations, we found that non-shared environmental, rather than genetic, influences explained much of the covariation between life events and depression symptoms. This suggests that whilst independent LEs may be heritable, the relationship is unlikely to be confounded by genetic influences and has significant implications for possible interventions for depression.

Arizona Twin Project: Specificity in Risk and Resilience for Developmental Psychopathology and Health

The Arizona Twin Project is an ongoing longitudinal study designed to elucidate gene-environment interplay underlying the development of risk and resilience to common mental and physical health problems during infancy, childhood and adolescence. Specificity of risk is carefully examined across mental and physical health and how these influences vary across socioeconomic and sociocultural environments. Participants are a sample of approximately 700 twins (31% Latinx) recruited from birth records in the state of Arizona, USA. Twins are 32% monozygotic twins, 36% same-sex dizygotic (DZ), 32% opposite-sex DZ, currently 10-11 years of age. Primary caregivers were interviewed on twins' development and early physical and social environments when twins were 1, 2 and 5 years of age. In-depth objective measurement commenced in middle childhood, with in-person assessments at 8-11 years of age, with plans to continue to follow the sample across adolescence. Middle childhood measures focus on children's physical and mental health, including diurnal cortisol, actigraphy-based measures of sleep and activity, cold pressor task assessing acute pain, and reaction time tasks assessing executive functioning. Preliminary findings illustrate that objective assessments of children's health are highly heritable, but they do not always share genetic etiology with more commonly used subjective assessments. Exposure to early adversity moderates genetic influences on both executive functioning and health, with higher heritability typically seen under adverse conditions. Future directions include an examination of how pubertal stage affects genetic and environmental influences on diurnal cortisol, sleep, chronic pain, and mental health.

Development of an individualized risk calculator for poor functioning in young people victimized during childhood: A longitudinal cohort study

BACKGROUND

Childhood victimization elevates the average risk of developing functional impairment in adulthood. However, not all victimized children demonstrate poor outcomes. Although research has described factors that confer vulnerability or resilience, it is unknown if this knowledge can be translated to accurately identify the most vulnerable victimized children.

OBJECTIVE

To build and internally validate a risk calculator to identify those victimized children who are most at risk of functional impairment at age 18 years.

PARTICIPANTS

We utilized data from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally-representative birth cohort of 2232 UK children born in 1994-95.

METHODS

Victimization exposure was assessed repeatedly between ages 5 and 12 years along with a range of individual-, family- and community-level predictors. Functional outcomes were assessed at age 18 years. We developed and evaluated a prediction model for psychosocial disadvantage and economic disadvantage using the Least Absolute Shrinkage and Selection Operator (LASSO) regularized regression with nested 10-fold cross-validation.

RESULTS

The model predicting psychosocial disadvantage following childhood victimization retained 12 of 22 predictors, had an area under the curve (AUC) of 0.65, and was well-calibrated within the range of 40-70% predicted risk. The model predicting economic disadvantage retained 10 of 22 predictors, achieved excellent discrimination (AUC = 0.80), and a high degree of calibration.

CONCLUSIONS

Prediction modelling techniques can be applied to estimate individual risk for poor functional outcomes in young adulthood following childhood victimization. Such risk prediction tools could potentially assist practitioners to target interventions, which is particularly useful in a context of scarce resources.

Continuity of genetic and environmental influences on clinically assessed major depression from ages 18 to 45

BACKGROUND

Studies on the stability of genetic risk for depression have relied on self-reported symptoms rather than diagnoses and/or short follow-up time. Our aim is to determine to what degree genetic and environmental influences on clinically assessed major depressive disorder (MDD) are stable between age 18 and 45.

METHODS

A population-based sample of 11 727 twins (6875 women) born between 1967 and 1991 was followed from 2006 to 2015 in health registry data from primary care that included diagnoses provided by treating physicians. Individuals with schizophrenia or bipolar disorder (n = 163) were excluded. We modelled genetic and environmental risk factors for MDD in an accelerated longitudinal design.

RESULTS

The best-fitting model indicated that genetic influences on MDD were completely stable from ages 18 to 45 and explained 38% of the variance. At each age, the environmental risk of MDD was determined by the risk at the preceding observation, plus new environmental risk, with an environmental correlation of +0.60 over 2 years. The model indicated no effects of shared environment and no environmental effects stable throughout the observational period. All long-term stability was therefore explained by genetic factors.

CONCLUSIONS

Different processes unfolded in the genetic and environmental risk for MDD. The genetic component is stable from later adolescence to middle adulthood and accounted for nearly all long-term stability. Therefore, molecular genetic studies can use age-heterogenous samples when investigating genetic risk variants of MDD. Environmental risk factors were stable over a short span of years with associations rapidly decreasing and no evidence of permanent environmental scarring.

Adolescents self-reported sleep quality and emotional regulation: a discordant twin study

AIM

This study explores the association between sleep quality and emotional regulation, and investigates the genetic and environmental bases of this association.

METHODS

Three-hundred-eighty-two adolescent twins, from the Italian Twin Registry, and their parents filled the Youth Self-Report and Child Behavior Checklist questionnaires, from which the construct of Effortful Control (EC) was derived as a measure of emotional regulation. Twins were identified as "good" or "non-good" sleepers based on answers to the Sleep Disorders Questionnaire. EC levels were compared between same-sex sleep discordant twins.

RESULTS

A significant association was detected between EC scores and sleep quality. When controlling for shared (fetal or early life) environmental factors and genetic background in the discordant twin analysis, this association weakened in dizygotic twins and disappeared in monozygotic twins.

CONCLUSION

Results support the association between sleep quality and EC in adolescence; furthermore, they suggest that sleep quality and emotional regulation may depend on common genetic or environmental factors.

Is aberrant affective cognition an endophenotype for affective disorders? - A monozygotic twin study

BACKGROUND

Identification of endophenotypes can improve prevention, detection and development of new treatments. We therefore investigated whether aberrant affective cognition constitutes an endophenotype for affective disorders by being present in monozygotic (MZ) twins with unipolar or bipolar disorder in partial remission (i.e. affected) and their unaffected co-twins (i.e. high-risk) relative to twins with no family history of affective disorder (i.e. low-risk).

METHODS

We conducted an assessor blind cross-sectional study from 2014 to 2017 of MZ twins using Danish population-based registers in recruitment. Twins attended one test session involving neurocognitive testing, clinical ratings and questionnaires. Main outcomes were attention to and recognition of emotional facial expressions, the memory of emotional self-referential words, emotion regulation and coping strategies.

RESULTS

Participants were 103 affected, 44 high-risk and 36 low-risk MZ twins. Groups were demographically well-balanced and showed comparable non-affective cognitive performance. We observed no aberrant affective cognition in affected and high-risk relative to low-risk twins. However, high-risk twins displayed attentional avoidance of emotional faces (ps ⩽ 0.009) and more use of task-oriented coping strategies (p = 0.01) compared with affected twins. In contrast did affected twins show more emotion-oriented coping than high- and low-risk twins (ps ⩽ 0.004).

CONCLUSIONS

Our findings provide no support of aberrant affective cognition as an endophenotype for affective disorders. High-risk twins' attentional avoidance of emotional faces and greater use of task-oriented coping strategies may reflect compensatory mechanisms.

Sluggish cognitive tempo: longitudinal stability and validity

Emerging research has identified sluggish cognitive tempo (SCT) as a construct separate from ADHD predominately inattentive presentation. The present study explores the longitudinal stability of SCT over a period of 7 years, specifically the independent effects of SCT on behavioural and academic outcomes concurrently over a 3-year period. A sample of 639 twins, aged 6-12 years, participating in the Western Reserve Reading and Math Project (WRRMP) were assessed at seven annual home visits. The WRRMP sample is an unselected sample of twins representative of the general population of typically developing school-age children. The current investigation will focus on parent and teacher reports which assess attention deficit hyperactive/impulsive disorder (ADHD) and standardized achievement measures which assess academic outcomes. Over periods longer than 1 or 2 years, SCT does not display good longitudinal stability (r < .60). SCT also does not have consistent significant independent effects on academic outcomes once the effects of ADHD were controlled for. Over a 7-year period, SCT does not demonstrate consistent longitudinal stability. SCT significantly predicts social problems, internalizing behaviours, and anxious/depressive behaviours after the effects of ADHD are controlled for. SCT has no significant independent effects on cognitive or educational outcomes after the effects of inattentive ADHD are controlled for.

Genetic Predisposition vs Individual-Specific Processes in the Association Between Psychotic-like Experiences and Cannabis Use

Importance

Previous research indicates that cannabis use is associated with psychotic-like experiences (PLEs). However, it is unclear whether this association results from predispositional (ie, shared genetic) factors or individual-specific factors (eg, causal processes, such as cannabis use leading to PLEs).

Objectives

To estimate genetic and environmental correlations between cannabis use and PLEs, and to examine PLEs in twin and nontwin sibling pairs discordant for exposure to cannabis use to disentangle predispositional from individual-specific effects.

Design, Setting, and Participants

In this cross-sectional analysis, diagnostic interviews and self-reported data were collected from 2 separate population-based samples of twin and nontwin sibling pairs. Data from the Human Connectome Project were collected between August 10, 2012, and September 29, 2015, and data from the Australian Twin Registry Cohort 3 (ATR3) were collected between August 1, 2005, and August 31, 2010. Data were analyzed between August 17, 2017, and July 6, 2018. The study included data from 1188 Human Connectome Project participants and 3486 ATR3 participants, totaling 4674 participants.

Main Outcomes and Measures

Three cannabis-involvement variables were examined: frequent use (ie, ≥100 times), a DSM-IV lifetime cannabis use disorder diagnosis, and current cannabis use. Genetic and environmental correlations between cannabis involvement and PLEs were estimated. Generalized linear mixed models examined PLE differences in twin and nontwin sibling pairs discordant for cannabis use.

Results

Among the 4674 participants, the mean (SD) age was 30.5 (3.2) years, and 2923 (62.5%) were female. Data on race/ethnicity were not included as a covariate owing to lack of variability within the ATR3 sample; among the 1188 participants in the Human Connectome Project, 875 (73.7%) were white. Psychotic-like experiences were associated with frequent cannabis use (β = 0.11; 95% CI, 0.08-0.14), cannabis use disorder (β = 0.13; 95% CI, 0.09-0.16), and current cannabis use (β = 0.07; 95% CI, 0.04-0.10) even after adjustment for covariates. Correlated genetic factors explained between 69.2% and 84.1% of this observed association. Within discordant pairs of twins/siblings (Npairs, 308-324), Psychotic-like experiences were more common in cannabis-exposed individuals compared with their relative who used cannabis to a lesser degree (β ≥ .23, P < .05; eg, frequent and infrequent cannabis-using relatives significantly differed, z = -5.41; P < .001).

Conclusions and Relevance

Despite the strong contribution of shared genetic factors, frequent and problem cannabis use also appears to be associated with PLEs via person-specific pathways. This study's findings suggest that policy discussions surrounding legalization should consider the influence of escalations in cannabis use on traitlike indices of vulnerability, such as PLEs, which could contribute to pervasive psychological and interpersonal burden.

A Twin Study of Normative Personality and DSM-IV Personality Disorder Criterion Counts: Evidence for Separate Genetic Influences

OBJECTIVE

Both normative personality and DSM-IV personality disorders have been found to be heritable. However, there is limited knowledge about the extent to which the genetic and environmental influences underlying DSM personality disorders are shared with those of normative personality. The aims of this study were to assess the phenotypic similarity between normative and pathological personality and to investigate the extent to which genetic and environmental influences underlying individual differences in normative personality account for symptom variance across DSM-IV personality disorders.

METHOD

A large population-based sample of adult twins was assessed for DSM-IV personality disorder criteria with structured interviews at two waves spanning a 10-year interval. At the second assessment, participants also completed the Big Five Inventory, a self-report instrument assessing the five-factor normative personality model. The proportion of genetic and environmental liabilities unique to the individual personality disorder measures, and hence not shared with the five Big Five Inventory domains, were estimated by means of multivariate Cholesky twin decompositions.

RESULTS

The median percentage of genetic liability to the 10 DSM-IV personality disorders assessed at wave 1 that was not shared with the Big Five domains was 64%, whereas for the six personality disorders that were assessed concurrently at wave 2, the median was 39%. Conversely, the median proportions of unique environmental liability in the personality disorders for wave 1 and wave 2 were 97% and 96%, respectively.

CONCLUSIONS

The results indicate that a moderate-to-sizable proportion of the genetic influence underlying DSM-IV personality disorders is not shared with the domain constructs of the Big Five model of normative personality. Caution should be exercised in assuming that normative personality measures can serve as proxies for DSM personality disorders when investigating the etiology of these disorders.

Stress reactivity links childhood trauma exposure to an admixture of depressive, anxiety, and psychosis symptoms

Childhood trauma exposure has been associated with a clinically relevant mixed phenotype of psychopathology composed of depressive, anxiety, and psychosis symptoms, across healthy and clinical samples. Altered stress-reactivity after exposure to childhood trauma may be a plausible underlying mechanism explaining this association. In a general population sample of female twins (T0 = 564; T1 = 483), associations between childhood trauma exposure and symptom profile (no symptoms, isolated symptoms, or a mixed phenotype) on the one hand, and daily life stress reactivity on the other were investigated. Daily life stress reactivity was measured using the Experience Sampling Method (ESM), and was defined as negative affect reactivity to minor daily life stressors. Individuals exposed to childhood trauma who reported a mixed phenotype of psychopathology showed a significant increase in emotional reactivity to daily life stress (activity and social stress), compared with trauma-exposed individuals without a mixed phenotype. In the trauma-exposed mixed phenotype group, increased emotional reactivity to event-stress predicted more severe symptoms at ± 14 month follow-up. This study found evidence that may link heightened emotional reactivity to stress in individuals with a trauma history to the risk for later comorbid psychopathology.

Grammar Clinical Marker Yields Substantial Heritability for Language Impairments in 16-Year-Old Twins

PURPOSE

There is a need for well-defined language phenotypes suitable for adolescents in twin studies and other large-scale research projects. Rice, Hoffman, and Wexler (2009) have developed a grammatical judgment measure as a clinical marker of language impairment, which has an extended developmental range to adolescence.

METHOD

We conducted the first twin analysis, along with associated phenotypic analyses of validity, of an abridged, 20-item version of this grammatical judgment measure (GJ-20), based on telephone administration using prerecorded stimuli to 405 pairs of 16-year-olds (148 monozygotic and 257 dizygotic) drawn from the Twins Early Development Study (Haworth, Davis, & Plomin, 2012).

RESULTS

The distribution of scores is markedly skewed negatively, as expected for a potential clinical marker. Low performance on GJ-20 is associated with lower maternal education, reported learning disability (age 7 years), and low scores on language tests administered via the Twins Early Development Study (age 16 years) as well as General Certificate of Secondary Education English and Math examination performance (age 16 years). Liability threshold estimates for the genetic influence on low performance on GJ-20 are substantial, ranging from 36% with a lowest 10% criterion to 74% for a lowest 5% criterion.

CONCLUSIONS

The heritability of GJ-20 scores, especially at more extreme cutoffs, along with the score distribution and association with other indicators of language impairments, provides additional evidence for the potential value of this measure as a clinical marker of specific language impairment.

Trajectories of Personality Traits Preceding Dementia Diagnosis

BACKGROUND

Several retrospective studies using informant report have shown that individuals with dementia demonstrate considerable personality change. Two prospective studies, also using informant report, have shown that individuals who develop dementia show some personality changes prior to diagnosis. The current study is the first to assess personality trait change prior to dementia diagnosis using self-report measures from longitudinal data.

METHOD

This study used data from the Swedish OCTO-Twin Study, a longitudinal panel of 702 twins aged 80 and older. Analysis was restricted to 86 individuals who completed the Eysenck Personality Inventory and received a dementia diagnosis during follow-up occasions. Latent growth curve analyses were used to examine trajectories of extraversion and neuroticism preceding dementia diagnosis.

RESULTS

Controlling for sex, age, education, depressive symptoms, and the interaction between age and education, growth curve analyses revealed a linear increase in neuroticism and stability in extraversion. Individuals who were eventually diagnosed with dementia showed a significant increase in neuroticism preceding diagnosis of dementia.

DISCUSSION

Personality change, specifically an increase in neuroticism, may be an early indicator of dementia. Identification of early indicators of dementia may facilitate development of screening assessments and aid in early care strategies and planning.

Weak associations between pubertal development and psychiatric and behavioral problems

Pubertal development has been associated with adverse outcomes throughout adolescence and adulthood. However, much of the previous literature has categorized outcome variables and pubertal timing measures for ease of mean difference or odds ratio interpretation. We use a UK-representative sample of over 5000 individuals drawn from the Twins Early Development Study to extend this literature by adopting an individual differences approach and emphasizing effect sizes. We investigate a variety of psychiatric and behavioral measures collected longitudinally at ages 11, 14 and 16, for multiple raters and for males and females separately. In addition, we use two measures of pubertal development: the Pubertal Development Scale at each age, as well as the age of menarche for girls. We found that pubertal development, however assessed, was linearly associated with a range of psychiatric and behavioral outcomes; however, the effect sizes of these associations were modest for both males and females with most correlations between -0.10 and 0.10. Our systematic analysis of associations between pubertal development, and psychiatric and behavioral problems is the most comprehensive to date. The results showing linearity of the effects of pubertal development support an individual differences approach, treating both pubertal development and associated outcomes as continuous rather than categorical variables. We conclude that pubertal development explains little variance in psychiatric and behavioral outcomes (<1% on average). The small effect sizes indicate that the associations are weak and should not warrant major concern at least in non-clinical populations.

"Holy anorexia"-relevant or relic? Religiosity and anorexia nervosa among Finnish women

Since medieval times, an association between religiosity and anorexia nervosa has been suggested, but few systematic studies exist. This study examines in a nationwide setting whether personal or family religiosity is associated with lifetime anorexia nervosa among women in adolescence and early adulthood. Women (N = 2,825) from the 1975 to 1979 birth cohorts of Finnish twins were screened for lifetime DSM-5 anorexia nervosa (N = 92). Parental religiosity was assessed by self-report when the women were aged 16 years. The women self-reported their religiosity at ages 16 and 22 to 27 years. Parental religiosity did not increase the risk of lifetime anorexia nervosa, and neither did religiosity of the women themselves in adolescence. In early adulthood, a J-shaped curve was compatible with the data, indicating increased risk both at low and high levels of religiosity, but this result was statistically non-significant. Religiosity was weakly negatively correlated with body dissatisfaction. There was some suggestive evidence for socioregional variation in the association of religiosity with lifetime anorexia nervosa. In this first population study to directly address religiosity and anorexia nervosa, no evidence was found for a significant association of religiosity with anorexia nervosa either at the personal or family level. Some regional differences are possible. A modest protective association of religiosity with body dissatisfaction is also possible. Despite compelling case descriptions of "holy anorexia," religiosity does not appear to be a central factor in the development of anorexia nervosa in Finland, a highly secularized Christian country.

Does the Environment Have an Enduring Effect on ADHD? A Longitudinal Study of Monozygotic Twin Differences in Children

Environmental factors play a key role in the development of Attention-Deficit/Hyperactivity Disorder (ADHD), but the long-term effects of these factors are still unclear. This study analyses data from 1024 monozygotic (identical) twins in Australia, the United States, and Scandinavia who were assessed for ADHD in Preschool, Kindergarten, Grade 1, and Grade 2. Differences within each twin pair were used as a direct measure of non-shared environmental effects. The Trait-State-Occasion (TSO) model developed by Cole et al. (Psychological Methods, 10, 3-20, 2005) was used to separate the non-shared environmental effects into stable factors, and transient factors that excluded measurement error. Stable factors explained, on average, 44 % and 39 % of the environmental variance in hyperactive-impulsive and inattentive symptoms, respectively. Transient effects explained the remaining 56 % and 60 % of variance. The proportion of stable variance was higher than expected based on previous research, suggesting promise for targeted interventions if future research identifies these stable risk factors.

Coordination difficulty and internalizing symptoms in adults: A twin/sibling study

Increased anxiety and depression symptoms have been reported in individuals with neurodevelopmental disorders, and have been found to be associated with motor coordination difficulties, but little is known about the etiology of these associations. This study aimed to assess genetic, shared (making twins/siblings alike) and non-shared (individual-specific) environmental influences on the association between poor coordination and symptoms of anxiety and depressed mood using a sample of adult twin and sibling pairs. Participants were asked about their coordination skill and anxiety and depression symptoms. About half of the variance in coordination difficulty was explained by familial (combined genetic and shared environmental) influences, with the remaining variance explained by non-shared environmental influences. Phenotypic associations between coordination and anxiety (r=.46) and depression symptoms (r=.44) were largely underpinned by shared familial liability for the three traits. Non-shared environment accounted for about a third of the phenotypic association. Results suggest that both familial and non-shared environmental influences play a role in the etiology of coordination difficulty and its association with internalizing symptoms. The current study highlights that both biological and environmental pathways shared between these symptoms should be examined in future research to inform prevention and treatment approaches in clinical settings.

The relationship between genetic and environmental influences on resilience and on common internalizing and externalizing psychiatric disorders

PURPOSE

Resilience to stressful life events (SLEs), which increase risk of psychopathology, is influenced by genetic factors. The purpose of this paper was to map the overlap of etiologic risk factors for resilience onto the broad psychopathological map. Resilience was defined as the difference between the twins' total score on a broad measure of internalizing symptoms and their predicted score based on their cumulative exposure to SLEs.

METHODS

Cholesky decompositions were performed with OpenMx to quantify the overlap in genetic and environmental risk factors between resilience and four phenotypes [major depression (MD), generalized anxiety disorder (GAD), alcohol abuse or dependence (AAD), and antisocial personality disorder (ASPD)].

RESULTS

The genetic factors that influence resilience account for 42 and 61 % of the heritability of MD and GAD, respectively, and 20 and 18 % for AAD and ASPD, respectively. The latent genetic contribution to MD was shared 47 % with resilience, and for AAD, this estimate was lower (23 %). The shared environmental covariance was nominal.

CONCLUSIONS

Genetic influences on resilience contribute to internalizing phenotypes to a higher degree than to externalizing phenotypes. Environmental influences can also have an enduring effect on resilience. However, virtually all of the covariance between resilience and the phenotypes was genetic.

What drives the association between weight-conscious peer groups and disordered eating? Disentangling genetic and environmental selection from pure socialization effects

Previous studies suggest strong associations between exposure to weight-conscious peer groups and increased levels of disordered eating. This association has been attributed to socialization effects (i.e., membership leads to disordered eating); however, selection effects (i.e., selecting into peer groups based on genetic and/or environmental predispositions toward disordered eating) could contribute to or even account for these associations. The current study was the first to use a co-twin control design to disentangle these types of selection factors from socialization effects. Participants included 610 female twins (ages 8-14) drawn from the Michigan State University Twin Registry. To comprehensively examine a range of eating pathology, several disordered eating attitudes and behaviors (e.g., body dissatisfaction, binge eating) were examined via self-report questionnaires. Questionnaires also were used to assess peer group emphasis on body weight and shape. Replicating previous results, significant individual-level associations were found between membership in weight-conscious peer groups and disordered eating. However, co-twin control analyses indicated that these associations were largely due to genetic and/or shared environmental selection factors rather than pure socialization effects. Importantly, results remained unchanged when controlling for pubertal status, suggesting that effects do not vary across developmental stage. Overall, these findings question whether associations between weight-conscious peer groups and disordered eating are due entirely to socialization processes. Future studies are needed to identify the specific genetic and/or shared environmental factors that may drive selection into weight-conscious peer groups.

Do sleep disturbances and psychotic-like experiences in adolescence share genetic and environmental influences?

Sleep disturbances regularly co-occur with clinical psychotic disorders and dimensions of psychotic-like experiences (PLEs). One possible explanation for this, which has yet to be tested, is that similar genetic or environmental influences underlie sleep disturbances and vulnerability to PLEs. We conducted a twin study to test this possibility in relation to sleep disturbances and six specific PLEs in adolescence in the general population. Approximately 5,000 16-year-old twin pairs completed the Pittsburgh Sleep Quality Index and Insomnia Severity Index. PLEs were assessed using the Specific PLEs Questionnaire, comprising five self-report subscales (Paranoia, Hallucinations, Cognitive Disorganization, Grandiosity, and Anhedonia) and one parent-report subscale (Negative Symptoms). The associations between these measures were tested using structural equation twin model fitting. Paranoia, Hallucinations, and Cognitive Disorganization displayed moderate and significant correlations with both sleep measures (0.32-.42), while Negative Symptoms, Anhedonia, and Grandiosity showed lower correlations (0.01-0.17). Genetic and environmental influences significantly overlapped across PLEs (Paranoia, Hallucinations, Cognitive Disorganization) and both types of sleep disturbance (mean genetic and nonshared environmental correlations = 0.54 and 0.24, respectively). These estimates reduced, yet remained significant, after controlling for negative affect. The association between PLEs with sleep disturbances in adolescence is partly due to genetic and environmental influences that are common to them both. These findings indicate that the known neurobiology of sleep disturbance may provide clues regarding the causes of PLEs in adolescence.

The Intergenerational Transmission of Anxiety: A Children-of-Twins Study

OBJECTIVE

The transmission of anxiety within families is well recognized, but the underlying processes are poorly understood. Twin studies of adolescent anxiety demonstrate both genetic and environmental influence, and multiple aspects of parenting are associated with offspring anxiety. To date, the children-of-twins design has not been used to evaluate the relative contributions of genetic transmission compared with direct transmission of anxiety from parents to their offspring.

METHOD

Anxiety and neuroticism measures were completed by 385 monozygotic and 486 dizygotic same-sex twin families (37% male twin pair families) from the Twin and Offspring Study in Sweden. Structural equation models tested for the presence of both genetic and environmental transmission from one generation to the next.

RESULTS

For both anxiety and neuroticism, the models provide support for significant direct environmental transmission from parents to their adolescent offspring. In contrast, there was no evidence of significant genetic transmission.

CONCLUSIONS

The association between parental and offspring anxiety largely arises because of a direct association between parents and their children independent of genetic confounds. The lack of genetic transmission may reflect there being different genetic effects on these traits in adolescence and adulthood. Direct environmental transmission is in line with developmental theories of anxiety suggesting that children and adolescents learn anxious behaviors from their parents through a number of pathways such as modeling. Future analyses should combine children-of-twins data with child twin data in order to examine whether this direct effect solely represents parental influences on the offspring or whether it also includes child/adolescent anxiety evoking parental anxiety.

Association of Protein Phosphatase PPM1G With Alcohol Use Disorder and Brain Activity During Behavioral Control in a Genome-Wide Methylation Analysis

OBJECTIVE

The genetic component of alcohol use disorder is substantial, but monozygotic twin discordance indicates a role for nonheritable differences that could be mediated by epigenetics. Despite growing evidence associating epigenetics and psychiatric disorders, it is unclear how epigenetics, particularly DNA methylation, relate to brain function and behavior, including drinking behavior.

METHOD

The authors carried out a genome-wide analysis of DNA methylation of 18 monozygotic twin pairs discordant for alcohol use disorder and validated differentially methylated regions. After validation, the authors characterized these differentially methylated regions using personality trait assessment and functional MRI in a sample of 499 adolescents.

RESULTS

Hypermethylation in the 3'-protein-phosphatase-1G (PPM1G) gene locus was associated with alcohol use disorder. The authors found association of PPM1G hypermethylation with early escalation of alcohol use and increased impulsiveness. They also observed association of PPM1G hypermethylation with increased blood-oxygen-level-dependent response in the right subthalamic nucleus during an impulsiveness task.

CONCLUSIONS

Overall, the authors provide first evidence for an epigenetic marker associated with alcohol consumption and its underlying neurobehavioral phenotype.

DSM-5 unspecified feeding and eating disorders in adolescents: what do they look like and are they clinically significant?

OBJECTIVE

The recent DSM-5 categorization of eating disorders introduces a new category of eating disorders, Unspecified Feeding and Eating Disorders (UFED), where symptoms do not meet criteria for any other diagnostic category, but cause clinically significant distress or impairment. The aim of the current study was to explore what disorders in UFED might look like in an adolescent population.

METHOD

We examined a large cohort of adolescent female twins (N = 699) who were assessed on three occasions and who did not meet a DSM-5 eating disorder diagnosis but who reported threshold levels of either fasting and/or driven exercise (N = 33; 4.7%). This group of girls was compared to girls who reported no eating disorder over the three waves, and girls who met a diagnosis of either anorexia nervosa (AN) or atypical AN.

RESULTS

The UFED group was characterized as being in the overweight range while striving to lose weight, and placing a high degree of importance on weight and shape in their self-evaluation. This group was indistinguishable from the two eating disorder groups on measures of global eating disorder severity, and demonstrated significantly elevated impairment and distress compared to the no eating disorder group commensurate with the eating disorder groups.

DISCUSSION

Further research of this group is necessary to ensure that these individuals are not overlooked, and that treatment options are appropriate and available.

Men's sexual interest in children: one-year incidence and correlates in a population-based sample of Finnish male twins

In a study of 1,310 Finnish adult male twins we found that sexual interest in children aged 12 or younger was reported by 0.2% of the sample. Sexual interest in children aged 15 or younger was reported by 3.3%. Participants reporting sexual interest in children aged 15 or younger were younger, reported stronger sexual desire, and had experienced more childhood sexual and nonsexual abuse. The present study is the first to give a population-based estimate of the incidence of sexual interest in children among adult men. The 12-month incidence of sexual interest in children below the age of 16 years is roughly comparable to the one-year incidence of major depression or the lifetime prevalence of transvestitic fetishism.

Cognitive performance and BMI in childhood: Shared genetic influences between reaction time but not response inhibition

OBJECTIVE

The aim of this work is to understand whether shared genetic influences can explain the association between obesity and cognitive performance, including slower and more variable reaction times (RTs) and worse response inhibition.

METHODS

RT on a four-choice RT task and the go/no-go task, and commission errors on the go/no-go task for 1,312 twins ages 7-10 years were measured. BMI was measured at 9-12 years. Biometric twin models were run to give an estimate of the genetic correlation (rG ) between body mass index (BMI) and three cognitive measures: mean RT (MRT), RT variability (RTV; the standard deviation of RTs), and commission errors (a measure of response inhibition).

RESULTS

Genetic correlations indicated that 20%-30% of the genes underlying BMI were shared with both RT measures. However, only small phenotypic correlations between MRT and RTV with later BMI (rPh  = ∼0.1) were observed. Commission errors were unassociated with later BMI (rPh  = -0.03, ns).

CONCLUSIONS

Our results are the first to demonstrate significant shared genetic effects between RT performance and BMI. Our findings add biological support to the notion that obesity is associated with slower and more variable RTs. However, our results also emphasize the small nature of the association, which may explain previous negative findings.

Genetic and environmental influences on adolescent rumination and its association with depressive symptoms

Rumination is an important cognitive vulnerability for adolescent and adult depression. However, little is known about the aetiological origins of rumination, as well as its association with depression. Adolescent rumination (self-report) and depressive symptoms (self- and parent-report) were assessed in 674 pairs of same-gender Chinese adolescent twins (11-17 years of age). Females accounted for 53.7 % of the sample. There were significant correlations between self-reported rumination and self-reported depression (r = 0.41), as well as parent-reported adolescent depression (r = 0.22). Genetic influences were significant and modest on all three measures, ranging from 24 % to 42 %. The three measures were also significantly influenced by shared environment, ranging from 20 % to 28 %, and non-shared environmental factors, ranging from 30 % to 56 %. Moreover, the genetic correlations between rumination and depression were significant (within-rater: r(g) = 0.99; cross-rater: r(g) = 0.59) and largely accounted for the phenotypic correlations (within-rater: 68 %; cross-rater: 77 %), while non-shared environmental correlations were also significant (within-rater: r(e) = 0.26; cross-rater: r(e) = 0.12) and accounted for the remainder of the phenotypic correlations (within-rater: 32 %; cross-rater: 23 %). The shared environmental correlations were non-significant. No significant gender and age differences were found in aetiological models. These findings suggest that rumination may be an endophenotype reflecting genetic risk for depression.

Sex differences in the pathways to major depression: a study of opposite-sex twin pairs

OBJECTIVE

The authors sought to clarify the nature of sex differences in the etiologic pathways to major depression.

METHOD

Retrospective and prospective assessments of 20 developmentally organized risk factors and the occurrence of past-year major depression were conducted at two waves of personal interviews at least 12 months apart in 1,057 opposite-sex dizygotic twin pairs from a population-based register. Analyses were conducted by structural modeling, examining within-pair differences.

RESULTS

Sixty percent of all paths in the best-fit model exhibited sex differences. Eleven of the 20 risk factors differed across sexes in their impact on liability to major depression. Five had a greater impact in women: parental warmth, neuroticism, divorce, social support, and marital satisfaction. Six had a greater impact in men: childhood sexual abuse, conduct disorder, drug abuse, prior history of major depression, and distal and dependent proximal stressful life events. The life event categories responsible for the stronger effect in males were financial, occupational, and legal in nature.

CONCLUSIONS

In a co-twin control design, which matches sisters and brothers on genetic and familial-environmental background, personality and failures in interpersonal relationships played a stronger etiologic role in major depression for women than for men. Externalizing psychopathology, prior depression, and specific "instrumental" classes of acute stressors were more important in the etiologic pathway to major depression for men. The results are consistent with previously proposed typologies of major depression that suggest two subtypes that differ in prevalence in women (deficiencies in caring relationships and interpersonal loss) and men (failures to achieve expected goals, with lowered self-worth).

Prosocial peer affiliation suppresses genetic influences on non-aggressive antisocial behaviors during childhood

BACKGROUND

Available research has suggested that affiliation with prosocial peers reduces child and adolescent antisocial behavior. However, the etiologic mechanisms driving this association remain unclear. The current study sought to evaluate whether this association takes the form of a gene-environment interaction (G × E) in which prosocial peer affiliation acts to reduce the consequences of genetic risk for non-aggressive antisocial behavior during childhood.

METHOD

Our sample consisted of 500 twin pairs aged 6-10 years from the Michigan State University Twin Registry (MSUTR).

RESULTS

The results robustly support moderation by prosocial peer affiliation. Genetic influences on non-aggressive antisocial behavior were observed to be several times larger in those with lower levels of prosocial peer affiliation than in those with higher levels of prosocial peer affiliation. This pattern of results persisted even after controlling for gene-environment correlations and deviant peer affiliation, and when restricting our analyses to those twins who shared all or nearly all of their friends.

CONCLUSIONS

Such findings not only suggest that prosocial peer affiliation moderates genetic influences on non-aggressive antisocial behaviors during childhood but also provide support for the theoretical notion that protective environmental experiences may exert their influence by promoting resilience to genetic risk.

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.

Concordant response to pharmacotherapy in monozygotic twins with schizoaffective disorder

Schizoaffective disorder (SAD) represents one of the most confusing and controversial concepts in psychiatry. Prevalence is less than 1%, but despite that it has a major influence on an individual and community. There is an increased risk for schizophrenia and mood diorders in first degree relatives with SAD, according to DSM IV. This paper describes the concordant clinical response of a pair of monozygotic twins with SAD when treated with risperidon and valproic acid. We found that their clinical symptoms were very similar and both brothers expressed hipomanic and depressive episode prior to full onset of SAD-psychotic symptoms with correlations of elevated mood, and first psychiatric hospitalization at the age of 19 (patient A) and 18 (patient B). Their response to the combined treatment with risperidon and valproic acid has been also similar both in intensity and in the pattern of symptoms that have improved.

Structure of genetic and environmental risk factors for symptoms of DSM-IV borderline personality disorder

IMPORTANCE

Previous studies have indicated that the psychopathological dimensions of borderline personality disorder (BPD) are influenced by a unitary liability factor. However, to our knowledge, the underlying etiological nature of the individual criteria for BPD as defined by the DSM-IV has not been explored.

OBJECTIVE

To determine the structure of genetic and environmental risk factors for the symptoms of BPD.

DESIGN, SETTING, AND PARTICIPANTS

Multivariate twin study with BPD criteria assessed by personal interview within a general community setting. Participants included 2794 young adults from the Norwegian Institute of Public Health Twin Panel.

MAIN OUTCOMES AND MEASURES

The 9 criteria for BPD assessed by the Structured Interview for DSM-IV Personality.

RESULTS

A common pathway model dominated by 1 highly heritable (55%) general BPD factor that strongly influenced all 9 BPD criteria (standardized path coefficients, 0.53-0.79) fit the data best. The model also included 2 additional common liability factors, mainly influencing criteria reflecting the affective and interpersonal dimensions. Both of these were mostly influenced by environmental liability factors (heritability, 29.3% and 2.2%). With 1 exception (criterion 2, unstable and intense relationships), the specific criteria were strongly influenced by environmental factors. Five of the 9 criterion-specific genetic effects were either 0 or negligible.

CONCLUSIONS AND RELEVANCE

These results indicate that most of the genetic effects on the individual BPD criteria derive from 1 highly heritable general BPD factor, whereas the environmental influences were mostly criterion specific.

Personality dimensions as common and broadband-specific features for internalizing and externalizing disorders

Several researchers have suggested that the nature of the covariation between internalizing and externalizing disorders may be understood better by examining the associations between temperament or personality and these disorders. The present study examined neuroticism as a potential common feature underlying both internalizing and externalizing disorders and novelty seeking as a potential broad-band specific feature influencing externalizing disorders alone. Participants were 12- to 18-year-old twin pairs (635 monozygotic twin pairs and 691 dizygotic twin pairs; 48 % male and 52 % female) recruited from the Colorado Center for Antisocial Drug Dependence. Genetic and nonshared environmental influences shared in common with neuroticism influenced the covariation among distinct internalizing disorders, the covariation among distinct externalizing disorders, and the covariation between internalizing and externalizing disorders. Genetic influences shared in common with novelty seeking influenced the covariation among externalizing disorders and the covariation between major depressive disorder and externalizing disorders, but not the covariation among internalizing disorders or between anxiety disorders and externalizing disorders. Also, after accounting for genetic and environmental influences shared in common with neuroticism and novelty seeking, there were no significant common genetic or environmental influences among the disorders examined, suggesting that the covariance among the disorders is sufficiently explained by neuroticism and novelty seeking. We conclude that neuroticism is a heritable common feature of both internalizing disorders and externalizing disorders, and that novelty seeking is a heritable broad-band specific factor that distinguishes anxiety disorders from externalizing disorders.

Religion/spirituality, risk, and the development of alcohol dependence in female twins

The contention that Religion/Spirituality (R/S) influences the development of alcohol dependence (AD) is increasingly supported, but risk factors have not been adequately examined together with protective R/S factors so as to determine the nature and relative strength of these domains at different stages in the development of alcoholism. Secondary data analysis of a sample of 4,002 young adult female twins used conditional Cox proportional hazards survival models to examine three distinct stages in the development of alcoholism: years to initiation of drinking, years from first drink to at-risk drinking, and years from at-risk drinking to AD. Risk and protective factors from models of alcoholism etiology and studies of R/S dimensionality were modeled simultaneously as predictors of each discrete stage and compared. Findings demonstrated that both risk factors and R/S variables influenced initiation of alcohol use; only R/S variables influenced subsequent progression to at-risk drinking; and risk factors primarily influenced further progression to AD. Protective factors (R/S variables being an exemplar) appeared to be critical determinants of intermediate-stage progression, thus suggesting that R/S factors and other psychosocial interventions might be particularly effective in delaying progression toward AD at this stage. In contrast, after the onset of at-risk drinking, the influence of (genetically based) risk factors appeared to accelerate AD regardless of most other influences. Thus, the timing of psychosocial interventions appears critical to their potency and impact.

Evidence for multiple genetic factors underlying DSM-IV criteria for major depression

IMPORTANCE

We do not know whether the clinical criteria for major depression (MD) reflect a single or multiple dimensions of genetic risk.

OBJECTIVE

To determine the structure of genetic and environmental risk factors for the 9 DSM-IV symptomatic MD criteria.

DESIGN

Population-based twin registry.

SETTING

Virginia.

PARTICIPANTS

Seven thousand five hundred members of adult twin pairs from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders.

MAIN OUTCOME MEASURE

Symptoms of lifetime MD as assessed at personal interview.

RESULTS

The best-fit twin model was multidimensional, requiring 3 genetic, 1 common environmental and 3 unique environmental common factors, and criterion-specific unique environmental factors. The first genetic factor was characterized by high loadings on cognitive and psychomotor depressive symptoms. The second and third genetic factors had strong loadings for mood and neurovegetative depressive symptoms, respectively. Genetic factor scores derived from these 3 factors differentially predicted patterns of comorbidity, other historical/clinical features of MD, and demographic variables. These results suggested that the first genetic factor reflected a general liability to internalizing disorders, while the third genetic factor was more specific for melancholic MD. The 3 unique environmental common factors reflected, respectively, global depressive, core mood, and cognitive depressive symptoms.

CONCLUSIONS AND RELEVANCE

The DSM-IV syndrome of MD does not reflect a single dimension of genetic liability. Rather, these criteria reflect 3 underlying dimensions that index genetic risk for cognitive/psychomotor, mood, and neurovegetative symptoms. While in need of replication, these results, validated by predictions using estimated genetic factor scores, have implications for gene-finding efforts for MD.

IGEMS: the consortium on Interplay of Genes and Environment across Multiple Studies

The Interplay of Genes and Environment across Multiple Studies (IGEMS) group is a consortium of eight longitudinal twin studies established to explore the nature of social context effects and gene-environment interplay in late-life functioning. The resulting analysis of the combined data from over 17,500 participants aged 25-102 at baseline (including nearly 2,600 monogygotic and 4,300 dizygotic twin pairs and over 1,700 family members) aims to understand why early life adversity, and social factors such as isolation and loneliness, are associated with diverse outcomes including mortality, physical functioning (health, functional ability), and psychological functioning (well-being, cognition), particularly in later life.

VETSA: the Vietnam Era Twin Study of Aging

The Vietnam Era Twin Study of Aging (VETSA) is a longitudinal behavioral genetic study with a primary focus on cognitive and brain aging in men. It comprises a subset of over 1,200 twins from the Vietnam Era Twin Registry. Like many other studies of aging, the VETSA includes many different phenotypes, but there are some key features that distinguish it from most other behavioral genetic aging studies. First, the initial assessment was conducted when all participants were middle-aged. Second, the age range of participants is narrow; all were in their 50s at the time of the initial recruitment. Third, the study includes an extensive and demanding neurocognitive test battery that was designed to provide good coverage of different cognitive abilities and avoid ceiling effects in middle-aged adults. Fourth, young adult cognitive test data (at an average age of 20 years) are available to provide a gauge of cognitive change. These features make the VETSA ideal for studying the heterogeneity of within-individual trajectories from midlife to old age, and for early detection of risk factors for cognitive decline.

Colorado Twin Registry: an update

The Colorado Twin Registry (CTR) is a population-based registry housed at the Institute for Behavioral Genetics at the University of Colorado. Recruitment began in 1982 and includes twins born from 1968 to the present. Four samples are currently drawn from the CTR: The Community Twin Sample, the Longitudinal Twin Sample, the Early Reading Development Sample, and the Colorado Learning Sample. Criteria for enrollment, recruitment strategies, demographic information, and zygosity assignment are explained for each sample. In addition, five studies in which CTR twins are now participating are highlighted. These include studies of cognition, learning ability, and vulnerability to substance abuse and antisocial behavior. The development of the CTR is an ongoing and evolving process, and it has proven to be a valuable registry, relatively representative of the population from which it was drawn.

The Early Growth and Development Study: a prospective adoption study from birth through middle childhood

The Early Growth and Development Study is a prospective adoption study of birth parents, adoptive parents, and adopted children recruited in two cohorts (N = 561 triads). The primary study aims are to examine how family, peer, and contextual processes affect children's adjustment, and to examine their interplay (mediation, moderation) with genetic influences. Participants were recruited through adoption agencies located throughout the United States following the birth of a child. Assessments are ongoing, in 9-month intervals until the child reaches 3 years of age and in 1-year intervals thereafter through age 9. Data collection includes the following primary constructs: child temperament, social behavior, school performance, mental health, and health; birth and adoptive parent personality characteristics, mental health, competence, stress, health, context, substance use, parenting, and marital relations; and pregnancy use of drugs and maternal stress during pregnancy. DNA and salivary cortisol samples have also been collected. Analyses have indicated evidence for genotype-environment interactions during early childhood. Study procedures, sample representativeness (including tests of potential confounds in the adoption design), and an overview of findings to date are summarized, and future plans are described.

The Colorado Adoption Project

This paper describes the Colorado Adoption Project (CAP), an ongoing genetically informative longitudinal study of behavioral development. We describe the features of the adoption design used in CAP, and discuss how this type of design uses data from both parent-offspring and related- versus unrelated-sibling comparisons to estimate the importance of genetic and shared environmental influences for resemblance among family members. The paper provides an overview of CAP's history, how subjects were ascertained, recruited, and retained, and the domains of assessment that have been explored since the CAP's initiation in 1975. Findings from some representative papers that make use of data from CAP participants illustrate the study's multifaceted nature as a parent-offspring and sibling behavioral genetic study, a study that parallels a complimentary twin study, a longitudinal study of development, a source of subjects for molecular genetic investigation, and a study of the outcomes of the adoption process itself. As subjects assessed first at age 1 approach age 40, we hope the CAP will establish itself as the first prospective adoption study of lifespan development.

Genetic and environmental stability in attention problems across the lifespan: evidence from the Netherlands twin register

OBJECTIVE

To review findings on attention-deficit/hyperactivity disorder and attention problems (AP) in children, adolescents, and adults, as established in the database of the Netherlands Twin Register and increase the understanding of stability in AP across the lifespan as a function of genetic and environmental influences.

METHOD

A longitudinal model was fitted on Netherlands Twin Register AP scores from 44,607 child (<12-year-old), adolescent (12- to 18-year-old), and adult (>18-year-old) twins.

RESULTS

Mean AP showed a downward trend with age. Age-to-age correlations ranged from 0.33 (50-≥60 years old) to 0.73 (10-12 years old). Stability in individual differences in AP was due to genetic and environmental factors, and change was due primarily to environmental factors. Nonadditive genetic influences were present from childhood to adulthood. Total genetic variance decreased slightly throughout aging, whereas environmental variance increased substantially with the switch from maternal to self-ratings at 12 years of age. As a result, heritability coefficients decreased from 0.70 to 0.74 in childhood (maternal ratings) to 0.51 to 0.56 in adolescence (self-ratings), and 0.40 to 0.54 in adulthood (self-ratings). In childhood, male subjects scored higher than female subjects. After the rater switch at 12 years of age, female subjects tended to score higher than male subjects.

CONCLUSIONS

Stability of AP is the result of genetic and environmental stability. The decrease in estimated heritability at 12 years of age is due to an increase in occasion-specific environmental variance and likely reflects a methodologic effect. Because environmental influences have lasting effects on AP, their early detection is crucial.

[Folie a deux: a nosographic question or just a shared madness?]

Folie a deux was described by Lasègue and Falret in 1877. The concept evolved thus giving rise to different variants of the same reported phenomenon. Taking a clinical case as an example, a review of the nosological definition of shared psychotic disorder was performed. Limitations were found in its descriptions of the subtypes of this unique clinical picture. In this paper we evaluate if its argument has real implications for the purpose of establishing a diagnosis and performing a definite therapeutic approach.

Clinical indices of familial alcohol use disorder

BACKGROUND

Alcohol use disorders (AUDs) are clinically heterogeneous and strongly influenced by familial/genetic factors. Can we identify specific clinical features of AUDs that index familial liability to illness?

METHODS

In twins from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders meeting DSM-IV criteria for lifetime AUDs, we examined whether clinical features of AUDs, including individual DSM-IV criteria for alcohol dependence (AD) and alcohol abuse (AA), predicted risk for AUDs in cotwins and/or parents. Analyses of individual criterion were repeated controlling for the total number of endorsed criteria.

RESULTS

Across these analyses, examining narrowly and broadly defined AUDs, risk of AUDs in relatives was more consistently predicted by abuse criteria than by dependence criteria, and by criteria reflecting negative psychosocial consequences rather than pharmacologic/biological criteria. Age at onset (AAO) poorly predicted risk in relatives. AUD associated legal problems, the one criterion slated for removal in DSM-5, was the most consistent single predictor of familial risk. Associations observed between individual criteria and risks of illness in relatives were generally stronger in monozygotic than dizygotic twin pairs, suggesting that these symptoms reflect a genetic risk for AUDs.

CONCLUSIONS

Individual DSM-IV criteria for AA and AD differ meaningfully in the degree to which they reflect the familial/genetic liability to AUDs. Contrary to expectation, the familial/genetic risk to AUDs was better reflected by symptoms of abuse and negative psychosocial consequences of AUD than by early AAO, or symptoms of tolerance and withdrawal.

Heritability of hallucinations in adolescent twins

Hallucinations are common in normal individuals and patients with schizophrenia and other psychotic disorders. Traditionally psycho-social approaches have emphasized the importance of environmental factors that contribute to variation of hallucinations. Using the Launay-Slade Hallucination Scale-Revised (LSHS-R), we investigated genetic and environmental influences on hallucinations in 598 pairs of healthy South Korean adolescent twins. Parameter estimates in the best-fitting model indicated that additive genetic and individual specific environmental factors for the LSHS-R were 33% (95% CI: 23-42%) and 67% (95% CI: 60-77%), respectively. There was no evidence for sex-specific genes for hallucinations. The magnitudes of genetic and environmental influences on hallucinations were similar in males and females. These results have implications in future molecular genetic studies that search for genes for hallucinations.

Math fluency is etiologically distinct from untimed math performance, decoding fluency, and untimed reading performance: evidence from a twin study

The authors examined whether math fluency was independent from untimed math and from reading using 314 pairs of school-aged twins drawn from the Western Reserve Reading and Math Projects. Twins were assessed through a 90-min home visit at approximately age 10 and were reassessed in their homes approximately 1 year later. Results suggested that the shared environment and genetics influenced the covariance among math fluency, untimed math measures, and reading measures. However, roughly two thirds of the variance in math fluency was independent from untimed math measures and reading, including reading fluency. The majority of this independent variance was the result of genetic factors that were longitudinally stable across two measurement occasions. These results suggest that math fluency, although related to other math measures, may also be a genetically distinct dimension of mathematics performance.

Lower birth weight indicates higher risk of autistic traits in discordant twin pairs

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder of complex etiology. Although strong evidence supports the causal role of genetic factors, environmental risk factors have also been implicated. This study used a co-twin-control design to investigate low birth weight as a risk factor for ASD.

METHOD

We studied a population-based sample of 3715 same-sex twin pairs participating in the Child and Adolescent Twin Study of Sweden (CATSS). ASD was assessed using a structured parent interview for screening of ASD and related developmental disorders, based on DSM-IV criteria. Birth weight was obtained from medical birth records maintained by the Swedish Medical Birth Registry.

RESULTS

Twins lower in birth weight in ASD-discordant twin pairs (n=34) were more than three times more likely to meet criteria for ASD than heavier twins [odds ratio (OR) 3.25]. Analyses of birth weight as a continuous risk factor showed a 13% reduction in risk of ASD for every 100 g increase in birth weight (n=78). Analysis of the effect of birth weight on ASD symptoms in the entire population (most of whom did not have ASD) showed a modest association. That is, for every 100 g increase in birth weight, a 2% decrease in severity of ASD indexed by scores on the Autism - Tics, attention-deficit hyperactivity disorder (AD/HD), and other Comorbidities (A-TAC) inventory would be expected in the sample as a whole.

CONCLUSIONS

The data were consistent with the hypothesis that low birth weight confers risk to ASD. Thus, although genetic effects are of major importance, a non-genetic influence associated with birth weight may contribute to the development of ASD.