Alessandra C. Iervolino

Prevalence and Heritability of Compulsive Hoarding: A Twin Study

OBJECTIVE Compulsive hoarding is a serious health problem for the sufferers, their families, and the community at large. It appears to be highly prevalent and to run in families. However, this familiality could be due to genetic or environmental factors. This study examined the prevalence and heritability of compulsive hoarding in a large sample of twins. METHOD A total of 5,022 twins completed a validated measure of compulsive hoarding. The prevalence of severe hoarding was determined using empirically derived cutoffs. Genetic and environmental influences on compulsive hoarding were estimated using liability threshold models, and maximum-likelihood univariate model-fitting analyses were employed to decompose the variance in the liability to compulsive hoarding into additive genetic and shared and nonshared environmental factors (female twins only; N=4,355). RESULTS A total of 2.3% of twins met criteria for caseness, with significantly higher rates observed for male (4.1%) than for female (2.1%) twins. Model-fitting analyses in female twins showed that genetic factors accounted for approximately 50% of the variance in compulsive hoarding, with nonshared environmental factors and measurement error accounting for the other half. CONCLUSIONS Compulsive hoarding is highly prevalent and heritable, at least in women, with nonshared environmental factors also likely to play an important role.

Genetic and environmental influences in adolescent peer socialization: evidence from two genetically sensitive designs

Harris argues that peer relationships are the chief determinants of personality development. Harriss thesis makes the behavioral genetic investigation of peer groups particularly timely. The present study examined genetic and environmental contribution to self-reported peer-group characteristics in two samples of adolescent siblings: 180 adoptive and nonadoptive sibling pairs from the Colorado Adoption Project, and 386 sibling pairs from the Nonshared Environment and Adolescent Development Study. Substantial genetic influence emerged for college orientation, with the remaining variance accounted for by nonshared environment. For delinquency, however, the majority of the variance was explained by nonshared environment. Although genetic influence was implicated for peer popularity in twin analyses, genetic factors were not important in explaining individual differences in nontwin siblings. These results suggest that although some dimensions of peers are somewhat mediated by genetic factors, nonshared environmental influence is substantial.

Environmental risk and young children’s cognitive and behavioral development

Using a longitudinal, large-scale sample of British twins, we addressed the prediction of both cognitive abilities and behavioral adjustment from eight domains of environmental risk: minority status, socio-economic status, maternal medical factors, twin medical factors, maternal depression, chaos within the home environment, and parental feelings towards their children and discipline. Participants included 5765 families with twins (49.1% male) born in 1994 and 1995. Aspects of environmental risk were assessed from birth until the children’s third birthdays; outcome measures were assessed at their fourth birthdays. Overall prediction of outcome (via multiple regression analysis) was moderate (R = .23 -.48). SES and chaos were the strongest predictors for the cognitive outcomes whereas for total behavior problems the more proximal parenting factors were also dominant. Future analyses will investigate these environmental risk indicators in the context of the genetically sensitive twin design.

Masculine Girls and Feminine Boys: Genetic and Environmental Contributions to Atypical Gender Development in Early Childhood.

In this genetic study of atypical gender role development, parents of 5,799 twin pairs, ages 3 and 4, rated their twin childrens masculinity and femininity. Boys were selected as gender atypical if they were highly feminine (top 5%, 10%, or 15%) relative to other boys, and girls were selected if they were highly masculine relative to other girls. Gender-atypical boys and girls were each divided into 2 groups: fully gender atypical (e.g., feminine boys also low on masculinity) and partially gender atypical (e.g., feminine boys who are not low on masculinity). DeFries-Fulker (DF; J. C. DeFries & D. W. Fulker, 1985, 1988) extremes analysis yielded moderate group heritability and substantial shared environment effects for atypical gender role behavior. However, for fully gender-atypical girls, group heritability accounted for most of the variance, and shared environment had no effect. The results are discussed in light of past studies and potential implications for atypical gender development.

Time trends in child and adolescent mental disorders

Purpose of review 1995 saw the publication of a major review of time trends in psychosocial disorders of youth across the second half of the twentieth century. It found evidence for substantial increases in rates of youth crime, alcohol and drug use, depression and suicide in most industrialized countries in the decades following the Second World War, slowing in some instances in the 1980s. Ten years on, we review findings on more recent trends in rates of these and other indicators of child and adolescent mental health. Recent findings Prevalence estimates for autism spectrum disorders have increased in recent decades, as has public and professional awareness of hyperactivity and attention deficits. Trends in adolescent conduct problems, and in alcohol and drug use, appear to reflect culture-specific influences. Rates of suicide among young males, and self-harm among females have risen in many countries in recent years; trends in emotional disorders are more varied, but there is little evidence for any rise in rates of anorexia nervosa. Although some contributors to these trends have been identified, much remains to be learned about the key risks involved. Summary Monitoring time trends in child and adolescent mental health is essential for service planning; knowledge of changing trends can also provide important pointers to potential risk factors. Current data sources allow relatively reliable tracking of trends in some areas, but remain severely limited in others. Further research is needed to understand the mechanisms underlying recently identified trends in child and adolescent mental health.

Stressful life events and material deprivation in hoarding disorder.

Traumatic life events and early material deprivation have been identified as potential environmental risk factors for the development of pathological hoarding behavior, but the evidence so far is preliminary and confounded by the presence of comorbid obsessive-compulsive disorder (OCD). This study retrospectively examined the occurrence of traumatic/stressful life events and material deprivation in four well-characterized groups: hoarding disorder without comorbid OCD (HD; n=24), hoarding disorder with comorbid OCD (HD+OCD; n=20), OCD without hoarding symptoms (OCD; n=17), and non-clinical controls (Control; n=20). Participants completed clinician and self-administered measures of hoarding, OCD, depression, psychological adjustment, and traumatic experience. Semi-structured interviews were undertaken to assess the temporal relation between traumatic/stressful life events and the onset and worsening of hoarding symptoms, and to determine the level of material deprivation. Although rates of post-traumatic stress disorder were comparable across all three clinical groups, hoarders (regardless of the presence of comorbid OCD) reported greater exposure to a range of traumatic and stressful life events compared to the two non-hoarding groups. Results remained unchanged after controlling for age, gender, education level, depression, and obsessive-compulsive symptoms. The total number of traumatic life events correlated significantly with the severity of hoarding but not of obsessive-compulsive symptoms. About half (52%) of hoarding individuals linked the onset of hoarding difficulties to stressful life circumstances, although this was significantly less common among those reporting early childhood onset of hoarding behavior. There was no link between levels of material deprivation and hoarding. Results support a link between trauma, life stress and hoarding, which may help to inform the conceptualization and treatment of hoarding disorder, but await confirmation in a representative epidemiological sample and using a longitudinal design.

A Multivariate Twin Study of Obsessive-Compulsive Symptom Dimensions

CONTEXT Obsessive-compulsive disorder (OCD) is clinically heterogeneous, but it is unclear whether this phenotypic heterogeneity reflects distinct, or partially distinct, etiologic mechanisms. OBJECTIVE To clarify the structure of the genetic and environmental risk factors for the major symptom dimensions of OCD. DESIGN Self-report questionnaires and multivariate twin model fitting. SETTING General community. PARTICIPANTS A total of 4355 female members of the TwinsUK adult twin register. MAIN OUTCOME MEASURES Scores on the Obsessive-Compulsive Inventory-Revised and 5 of its subscales (checking, hoarding, obsessing, ordering, and washing). RESULTS A common pathway model did not fit the data well, indicating that no single latent factor can explain the heterogeneity of OCD. The best-fit multivariate twin model was an independent pathway model, whereby both common and unique genetic and/or environmental factors contribute to the etiology of each symptom dimension. The hoarding dimension had the lowest loading on the common factor and was more influenced by specific genetic effects (54.5% specific). With the exception of hoarding, most of the genetic variance was due to shared genetic factors (ranging from 62.5% to 100%), whereas most of the nonshared environmental variance was due to dimension-specific factors. CONCLUSIONS Obsessive-compulsive disorder is unlikely to be an etiologically homogeneous condition. There is substantial etiologic overlap across the different OC symptom dimensions, but dimension-specific genetic, and particularly nonshared environmental, factors are at least as important. Hoarding shares the least amount of genetic liability with the remaining symptom dimensions. The results have implications for the current deliberations regarding OCD and the inclusion of a putative hoarding disorder in DSM-5.

Experiential avoidance and emotion regulation difficulties in hoarding disorder

Experiential avoidance can be defined as the tendency to avoid contact with unwanted internal experiences. Current conceptualizations of pathological hoarding appear broadly consistent with an experiential avoidant model. Eighty participants in four groups, namely hoarding disorder (HD) without comorbid obsessive-compulsive disorder (OCD), HD with comorbid OCD, non-hoarding OCD, and healthy controls, were administered measures of experiential avoidance and emotion regulation difficulties. Hoarding individuals reported higher levels of experiential avoidance and difficulties in emotion regulation compared to healthy but not to OCD participants. Both experiential avoidance and emotion regulation difficulties were significantly more prominent when HD was comorbid with OCD than when HD occurred without comorbid OCD. Correlation analyses further showed that both experiential avoidance and emotion regulation were moderately but significantly associated with obsessive-compulsive but not hoarding symptoms. Thus, experiential avoidance and emotion regulation difficulties are not specifically relevant to HD but to a broad range of psychopathologies. However, despite the lack of specificity, the findings raise some potentially useful clinical implications for the treatment of HD.

Evidence for a genetic overlap between body dysmorphic concerns and obsessive-compulsive symptoms in an adult female community twin sample.

Body dysmorphic disorder (BDD) is thought to be etiologically related to obsessive–compulsive disorder (OCD) but the available evidence is incomplete. The current study examined the genetic and environmental sources of covariance between body dysmorphic and obsessive–compulsive symptoms in a community sample of adult twins. A total of 2,148 female twins (1,074 pairs) completed valid and reliable measures of body dysmorphic concerns and obsessive–compulsive symptoms. The data were analyzed using bivariate twin modeling methods and the statistical programme Mx. In the best‐fitting model, the covariation between body dysmorphic and obsessive–compulsive traits was largely accounted for by genetic influences common to both phenotypes (64%; 95% CI: 0.50–0.80). This genetic overlap was even higher when specific obsessive–compulsive symptom dimensions were considered, with up to 82% of the phenotypic correlation between the obsessing and symmetry/ordering symptom dimensions and dysmorphic concerns being attributable to common genetic factors. Unique environmental factors, although influencing these traits individually, did not substantially contribute to their covariation. The results remained unchanged when excluding individuals reporting an objective medical condition/injury accounting for their concern in physical appearance. The association between body dysmorphic concerns and obsessive–compulsive symptoms is largely explained by shared genetic factors. Environmental risk factors were largely unique to each phenotype. These results support current recommendations to group BDD together with OCD in the same DSM‐5 chapter, although comparison with other phenotypes such as somatoform disorders and social phobia is needed.

A twin study of body dysmorphic concerns.

BACKGROUND Dysmorphic concern refers to an excessive preoccupation with a perceived or slight defect in physical appearance. It lies on a continuum of severity from no or minimal concerns to severe concerns over ones appearance. The present study examined the heritability of dysmorphic concerns in a large sample of twins. METHOD Twins from the St Thomas UK twin registry completed a valid and reliable self-report measure of dysmorphic concerns, which also includes questions about perceived body odour and malfunction. Twin modelling methods (female twins only, n=3544) were employed to decompose the variance in the liability to dysmorphic concerns into additive genetic, shared and non-shared environmental factors. RESULTS Model-fitting analyses showed that genetic factors accounted for approximately 44% [95% confidence intervals (CI) 36-50%] of the variance in dysmorphic concerns, with non-shared environmental factors and measurement error accounting for the remaining variance (56%; 95% CI 50-63%). Shared environmental factors were negligible. The results remained unchanged when excluding individuals reporting an objective medical condition/injury accounting for their concern in physical appearance. CONCLUSIONS Over-concern with a perceived or slight defect in physical appearance is a heritable trait, with non-shared environmental factors also playing an important role in its causation. The results are relevant for various psychiatric disorders characterized by excessive concerns in body appearance, odour or function, including but not limited to body dysmorphic disorder.