Obsessive-compulsive disorder phenotypes: implications for genetic studies

Shared executive dysfunctions in unaffected relatives of patients with autism and obsessive-compulsive disorder

BACKGROUND

Executive dysfunctions have been studied as a potential endophenotype associated with the genetic basis of autism. Given that recent findings from clinical and molecular genetic studies suggest that autism and obsessive-compulsive disorder (OCD) could share a common pattern of heritability, we assessed executive functions as a possible common cognitive endophenotype in unaffected family members of individuals with either autism or OCD.

METHODS

Five tests assessing executive functions (Tower of London, verbal fluency, design fluency, trail making and association fluency) were proposed to 58 unaffected first-degree relatives (parents and siblings) of probands with autism and 64 unaffected first-degree relatives of OCD patients. Results were compared with those of 47 healthy controls matched for age, sex, and level of education.

RESULTS

In the Tower of London test, both groups of unaffected relatives showed significantly lower scores and longer response times compared with controls. No differences were observed between autism and OCD relatives and healthy controls in the four other tasks (verbal fluency, design fluency, trail making test and association fluency).

CONCLUSIONS

Our findings show the existence of executive dysfunction in the unaffected first-degree relatives of probands with OCD, similar to those observed in the relatives of patients with autism. These results support and extend previous cognitive studies on probands indicating executive dysfunctions in autism and OCD. Planning and working memory processes could thus represent a common cognitive endophenotype in autism and OCD that could help in the identification of genes conferring vulnerability to these disorders.

What is the optimal way to subdivide obsessive-compulsive disorder?

The clinical presentation of obsessive-compulsive disorder (OCD) varies not only across patients but over the course of the disorder. This diversity indicates that OCD is a heterogeneous disorder, which may have an important impact on psychopathological, longitudinal, genetic, and treatment research. To better understand OCD heterogeneity, more homogeneous phenotypic descriptions are necessary to delimiting clinically meaningful subgroups of patients. Besides phenotypic descriptions, another method of delimiting OCD patient subgroups includes the search for endophenotypes (extended phenotypes) based on neurophysiological, immunological, genetic, neuropsychological, or neuroanatomic (neuroimaging) paradigms. This article will describe some strategies that deal with OCD heterogeneity, including the identification of more homogeneous phenotypical categories, an improved understanding of obsessive-compulsive symptom dimensions and how to use them as quantitative traits, and broadening the diagnostic boundaries of OCD to include other related conditions. The relevance and limitations of each approach are also discussed. Since the etiological mechanisms associated with the expressions of OCD are unknown, there is probably not one but several heuristic strategies to search for more homogeneous OCD subgroup, that combined may provide the most fruitful results.

Chronic tics and Tourette syndrome in patients with obsessive-compulsive disorder

Tourette syndrome (TS) and chronic motor/vocal tics (CMVT) are both common disorders in patients with obsessive compulsive disorder (OCD). However, there have been few studies evaluating the differences between the OCD with TS and OCD with CMVT subgroups. This study was conducted in order to further investigate possible differences between the expression of the OCD phenotype in OCD with TS and that seen in OCD with CMVT. One hundred and fifty-nine outpatients referred to an OCD research program were evaluated using the following instruments: the Structured Clinical Interview for DSM-IV; the Yale-Brown Obsessive Compulsive Scale; the Yale Global Tic Severity Scale; and the USP-HARVARD Repetitive Behaviors Interview. Patients were divided into three groups: OCD patients without tics (OCD-TICS, n=98), OCD patients with chronic motor or vocal tics (OCD+CMVT, n=31) and OCD patients with TS (OCD+TS, n=30). OCD+CMVT patients were similar to OCD+TS patients regarding the frequency of intrusive sounds, repeating behaviors, counting and tic-like compulsions (in both cases more frequent than in OCD-TICS patients). For age at obsessive-compulsive (OC) symptom onset, sensory phenomena score, number of comorbidities, frequency of somatic obsessions, bodily sensations and just-right perceptions, OCD+CMVT patients tended to be in between the other two groups. Our results suggest that there are qualitative and quantitative differences in the phenotypic expression of tic disorders in OCD patients, depending on whether the subject has TS or only CMVT.

The genetic studies of obsessive-compulsive disorder and its future directions

Obsessive-compulsive disorder (OCD) is characterized by recurrent and persistent thoughts (obsessions), and repetitive behaviors or mental acts (compulsions). In Korea, an epidemiological study reported that the lifetime prevalence of OCD in the population was greater than two percent. The exact cause of OCD is still unknown. Evidence from familial, twin and segregation studies supports the role of a genetic component in the etiology of OCD. In addition, there is growing evidence that OCD has a specific neurochemical and neuroanatomical basis. According to this evidence, researchers have selected various candidate genes which have been implicated in the neurophysiology of OCD, and differences of allelic variants in OCD patients and controls have been analyzed. In this review we will introduce the results of previous genetic studies of OCD which have been performed in other populations, including twin studies, family studies, segregation analyses, linkage analyses, and association studies. In addition to these studies, we will present the results of our genetic studies of OCD performed in Korea.

Genetics in eating disorders: extending the boundaries of research

OBJECTIVE: To review the recent literature relevant to genetic research in eating disorders and to discuss unique issues which are crucial for the development of a genetic research project in eating disorders in Brazil. METHOD: A computer literature review was conducted in the Medline database between 1984 and may 2005 with the search terms "eating disorders", "anorexia nervosa", "bulimia nervosa", "binge eating disorder", "family", "twin" and "molecular genetic" studies. RESULTS: Current research findings suggest a substantial influence of genetic factors on the liability to anorexia nervosa and bulimia nervosa. Genetic research with admixed populations should take into consideration sample size, density of genotyping and population stratification. Through admixture mapping it is possible to study the genetic structure of admixed human populations to localize genes that underlie ethnic variation in diseases or traits of interest. CONCLUSIONS: The development of a major collaborative genetics initiative of eating disorders in Brazil and South America would represent a realistic possibility of studying the genetics of eating disorders in the context of inter ethnic groups, and also integrate a new perspective on the biological etiology of eating disorders.

Genomewide linkage scan for obsessive-compulsive disorder: evidence for susceptibility loci on chromosomes 3q, 7p, 1q, 15q, and 6q

Obsessive-compulsive disorder (OCD) is the tenth most disabling medical condition worldwide. Twin and family studies implicate a genetic etiology for this disorder, although specific genes have yet to be identified. Here, we present the first large-scale model-free linkage analysis of both extended and nuclear families using both 'broad' (definite and probable diagnoses) and 'narrow' (definite only) definitions of OCD. We conducted a genome-scan analysis of 219 families collected as part of the OCD Collaborative Genetics Study. Suggestive linkage signals were revealed by multipoint analysis on chromosomes 3q27-28 (P=0.0003), 6q (P=0.003), 7p (P=0.001), 1q (P=0.003), and 15q (P=0.006). Using the 'broad' OCD definition, we observed the strongest evidence for linkage on chromosome 3q27-28. The maximum overall Kong and Cox LODall score (2.67) occurred at D3S1262 and D3S2398, and simulation based P-values for these two signals were 0.0003 and 0.0004, respectively, although for both signals, the simulation-based genome-wide significance levels were 0.055. Covariate-linkage analyses implicated a possible role of gene(s) on chromosome 1 in increasing the risk for an earlier onset form of OCD. We are currently pursuing fine mapping in the five regions giving suggestive signals, with a particular focus on 3q27-28. Given probable etiologic heterogeneity in OCD, mapping gene(s) involved in the disorder may be enhanced by replication studies, large-scale family-based linkage studies, and the application of novel statistical methods.

The normalcy of neurosis: evolutionary origins of obsessive-compulsive disorder and related behaviors

One of the most curious questions plaguing subscribers of evolutionary theory is how natural selection's fine-tuned editing function could allow disease to persist. For evolutionary psychiatrists, the existence of psychopathology is thus perplexing. To illustrate a potential answer to one instance of this broad question, we examine the correlates of obsessive-compulsive disorder (OCD) within our normal repertoire of thought and action. The evidence presents a picture of OCD as a dysregulation of normal behaviors and mental states throughout the course of human development. We speculate that such correspondence may be more than a coincidence and that OCD is a consequence of a dysregulation of the neural circuits that are crucially involved in threat detection and harm avoidance. These neural systems are also likely to underlie aspects of religious experience and ritual as well as the wonders of romantic and early parental love.

Common and distinct neural correlates of obsessive-compulsive and related disorders

Obsessive-compulsive disorder (OCD) often co-occurs with other anxiety disorders and a number of other disorders of similar phenomenology known as the "OCD spectrum" disorders. Neurobiologically, it is unclear how all these disorders relate to each other. The picture is further complicated by the clinical heterogeneity of OCD itself. This article reviews the literature on the common and distinct neural correlates of OCD, its symptom dimensions, and other anxiety and OCD spectrum disorders with the hope of providing a conceptual and heuristic framework to help understand the relationship between these phenomena.

Does work on obsessive-compulsive spectrum disorders contribute to understanding the heterogeneity of obsessive-compulsive disorder?

BACKGROUND

There is a growing literature on the concept of an obsessive-compulsive spectrum of disorders. Here, we consider the different dimensions on which obsessive-compulsive spectrum (OCSDs) lie, and focus on how the concepts from this literature may help understand the heterogeneity of obsessive-compulsive disorder (OCD).

METHODS

A computerized literature search (MEDLINE: 1964-2005) was used to collect studies addressing different dimensions on which the OCSDs lie. Against this backdrop, we report on a cluster analysis of OCSDs within OCD.

RESULTS

OCSDs may lie on several different dimensions. Our cluster analysis found that in OCD there were 3 clusters of OCD spectrum symptoms: (1) "Reward deficiency" (including trichotillomania, pathological gambling, hypersexual disorder and Tourette's disorder), (2) "Impulsivity" (including compulsive shopping, kleptomania, eating disorders, self-injury and intermittent explosive disorder), and (3) "Somatic" (including body dysmorphic disorder and hypochondriasis).

CONCLUSIONS

It is unlikely that OC symptoms and disorders fall on any single phenomenological dimension; instead, multiple different constructs may be required to map this nosological space. Although there is evidence for the validity of some of the relevant dimensions, additional work is required to delineate more fully the endophenotypes that underlie OC symptoms and disorders.

The Dimensional Yale-Brown Obsessive-Compulsive Scale (DY-BOCS): an instrument for assessing obsessive-compulsive symptom dimensions

Obsessive-compulsive disorder (OCD) encompasses a broad range of symptoms representing multiple domains. This complex phenotype can be summarized using a few consistent and temporally stable symptom dimensions. The objective of this study was to assess the psychometric properties of the Dimensional Yale-Brown Obsessive-Compulsive Scale (DY-BOCS). This scale measures the presence and severity of obsessive-compulsive (OC) symptoms within six distinct dimensions that combine thematically related obsessions and compulsions. The DY-BOCS includes portions to be used as a self-report instrument and portions to be used by expert raters, including global ratings of OC symptom severity and overall impairment. We assessed 137 patients with a Diagnostic and Statistical Manual-IV diagnosis of OCD, aged 6-69 years, from sites in the USA, Canada and Brazil. Estimates of the reliability and validity of both the expert and self-report versions of the DY-BOCS were calculated and stratified according to age (pediatric vs. adult subjects). The internal consistency of each of the six symptom dimensions and the global severity score were excellent. The inter-rater agreement was also excellent for all component scores. Self-report and expert ratings were highly intercorrelated. The global DY-BOCS score was highly correlated with the total Yale-Brown Obsessive-Compulsive Scale score (Pearson r = 0.82, P<0.0001). Severity scores for individual symptom dimensions were largely independent of one another, only modestly correlated with the global ratings, and were also differentially related to ratings of depression, anxiety and tic severity. No major differences were observed when the results were stratified by age. These results indicate that the DY-BOCS is a reliable and valid instrument for assessing multiple aspects of OCD symptom severity in natural history, neuroimaging, treatment response and genetic studies when administered by expert clinicians or their highly trained staff.

Psychiatric endophenotypes and the development of valid animal models

Endophenotypes are quantifiable components in the genes-to-behaviors pathways, distinct from psychiatric symptoms, which make genetic and biological studies of etiologies for disease categories more manageable. The endophenotype concept has emerged as a strategic tool in neuropsychiatric research. This emergence is due to many factors, including the modest reproducibility of results from studies directed toward etiologies and appreciation for the complex relationships between genes and behavior. Disease heterogeneity is often guaranteed, rather than simplified, through the current diagnostic system; inherent benefits of endophenotypes include more specific disease concepts and process definitions. Endophenotypes can be neurophysiological, biochemical, endocrine, neuroanatomical, cognitive or neuropsychological. Heritability and stability (state independence) represent key components of any useful endophenotype. Importantly, they characterize an approach that reduces the complexity of symptoms and multifaceted behaviors, resulting in units of analysis that are more amenable to being modeled in animals. We discuss the benefits of more direct interpretation of clinical endophenotypes by basic behavioral scientists. With the advent of important findings regarding the genes that predispose to psychiatric illness, we are at an important crossroads where, without anthropomorphizing, animal models may provide homologous components of psychiatric illness, rather than simply equating to similar (loosely analogized) behaviors, validators of the efficacy of current medications or models of symptoms. We conclude that there exists a need for increased collaboration between clinicians and basic scientists, the result of which should be to improve diagnosis, classification and treatment on one end and to increase the construct relevance of model organisms on the other.

Deconstructing obsessive-compulsive disorder: a multidimensional perspective

PURPOSE OF REVIEW

The aim of this article is to critically summarize the most promising attempts to split obsessive-compulsive disorder into subgroups based on clinical characteristics (i.e. age of onset, presence of comorbid tics, positive family history) and symptom theme, with particular emphasis on the latter.

RECENT FINDINGS

Attempts to split obsessive-compulsive disorder into mutually exclusive sub-groups based on clinical characteristics have been useful but not exempt of problems. The complex clinical presentation of the condition can be reduced to a few consistent, temporally stable symptom dimensions that can coexist in any given individual. Researchers have begun to investigate the genetics and neural mechanisms of these symptom dimensions and to develop specific assessment and treatment protocols for each particular problem.

SUMMARY

The multidimensional model of obsessive-compulsive disorder proposes a middle ground between the 'lumping' and 'splitting' perspectives. The disorder can be better understood as a spectrum of multiple potentially overlapping syndromes. The most fruitful research strategy will be to examine the common and specific etiological factors implicated in each symptom dimension.

Psychopharmacologic treatment of pediatric anxiety disorders

This article reviews the psychopharmacologic treatment of child and adolescent anxiety disorders and is divided into the following sections: historical background, general treatment principles, obsessive-compulsive disorder, other anxiety disorders, including separation anxiety disorders, generalized anxiety disorder, and social phobia, elective mutism, and post-traumatic stress disorder and specific phobia. Short-term and long-term psychopharmacologic treatment strategies are reviewed, as are approaches for managing comorbidity and treatment-refractory cases. This article is organized by diagnostic categories rather than by medication classes to emphasize the clinical perspective.