A population-based family clustering study of tic-related obsessive-compulsive disorder

Towards zebrafish models to unravel translational insights of obsessive-compulsive disorder: A neurobehavioral perspective

Obsessive-compulsive disorder (OCD) is a chronic and debilitating illness that has been considered a polygenic and multifactorial disorder, challenging effective therapeutic interventions. Although invaluable advances have been obtained from human and rodent studies, several molecular and mechanistic aspects of OCD etiology are still obscure. Thus, the use of non-traditional animal models may foster innovative approaches in this field, aiming to elucidate the underlying mechanisms of disease from an evolutionary perspective. The zebrafish (Danio rerio) has been increasingly considered a powerful organism in translational neuroscience research, especially due to the intrinsic features of the species. Here, we outline target mechanisms of OCD for translational research, and discuss how zebrafish-based models can contribute to explore neurobehavioral aspects resembling those found in OCD. We also identify possible advantages and limitations of potential zebrafish-based models, as well as highlight future directions in both etiological and therapeutic research. Lastly, we reinforce the use of zebrafish as a promising tool to unravel the biological basis of OCD, as well as novel pharmacological therapies in the field.

Latin American Trans-ancestry INitiative for OCD genomics (LATINO): Study protocol

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder. Worldwide, its prevalence is ~2% and its etiology is mostly unknown. Identifying biological factors contributing to OCD will elucidate underlying mechanisms and might contribute to improved treatment outcomes. Genomic studies of OCD are beginning to reveal long-sought risk loci, but >95% of the cases currently in analysis are of homogenous European ancestry. If not addressed, this Eurocentric bias will result in OCD genomic findings being more accurate for individuals of European ancestry than other ancestries, thereby contributing to health disparities in potential future applications of genomics. In this study protocol paper, we describe the Latin American Trans-ancestry INitiative for OCD genomics (LATINO, https://www.latinostudy.org). LATINO is a new network of investigators from across Latin America, the United States, and Canada who have begun to collect DNA and clinical data from 5000 richly phenotyped OCD cases of Latin American ancestry in a culturally sensitive and ethical manner. In this project, we will utilize trans-ancestry genomic analyses to accelerate the identification of OCD risk loci, fine-map putative causal variants, and improve the performance of polygenic risk scores in diverse populations. We will also capitalize on rich clinical data to examine the genetics of treatment response, biologically plausible OCD subtypes, and symptom dimensions. Additionally, LATINO will help elucidate the diversity of the clinical presentations of OCD across cultures through various trainings developed and offered in collaboration with Latin American investigators. We believe this study will advance the important goal of global mental health discovery and equity.

Altered Error Monitoring and Decreased Flanker Task Accuracy in Pediatric Obsessive-Compulsive Disorder

The error-related negativity (ERN) and error positivity (Pe) are components of the event-related potential following an error that are potential mechanistic biomarkers of obsessive-compulsive disorder (OCD). The study examined the ERN, Pe, flanker task accuracy, and clinical measures in 105 OCD cases and 105 matched healthy controls (HC) ages 8-18 years. Higher flanker task accuracy in all participants was associated with an increased ERN amplitude and increased difference between Pe and correct positivity amplitudes (ΔPe). Compared to HC, OCD cases had an increased ERN but decreased ΔPe and flanker task accuracy. Those differences were also significant in tic-related and non-tic-related OCD cases compared to HC. A lower ΔPe was associated in cases with an earlier age at OCD symptom onset. The results support the hypothesis that OCD involves defects in an error monitoring system and suggest a reduced ΔPe may compromise error signaling and cause uncertainty about the correctness of a response.

Altered Error Monitoring and Decreased Flanker Task Accuracy in Pediatric Obsessive-Compulsive Disorder

The error-related negativity (ERN) and error positivity (Pe) are components of the event-related potential following an error that are potential mechanistic biomarkers of obsessive-compulsive disorder (OCD). The study examined the ERN, Pe, flanker task accuracy, and clinical measures in 105 OCD cases and 105 matched healthy controls (HC), ages 8 to 18 years, with 21 cases having a tic disorder history. Higher flanker task accuracy in all participants was associated with an increased ERN amplitude and increased difference between Pe and correct positivity amplitudes (ΔPe). Compared to HC, OCD cases had an increased ERN but decreased flanker task accuracy and ΔPe. Those differences were also significant in tic-related and non-tic-related OCD cases compared to HC. A lower ΔPe was associated in OCD cases with an earlier age at OCD symptom onset. The results support the hypothesis that OCD involves defects in an error monitoring system and suggest a reduced ΔPe may compromise error signaling and cause uncertainty about the correctness of a response.

Use of Post-mortem Brain Tissue in Investigations of Obsessive- Compulsive Disorder: A Systematic Review

BACKGROUND

Post-mortem examination of the brain is a key strategy to increase our understanding of the neurobiology of mental disorders. While extensive post-mortem research has been undertaken on some mental disorders, others appear to have been relatively neglected.

OBJECTIVE

The objective of the study was to conduct a systematic review of post-mortem research on obsessive-compulsive disorder (OCD).

METHODS

A systematic review was performed in accordance with PRISMA guidelines to provide an overview of quantitative, qualitative, or mixed methods primary research studies on OCD. Search platforms included NCBI Pubmed, SCOPUS, and Web of Science.

RESULTS

A total of 52 publications were found, and after the removal of works not meeting the inclusion criteria, six (6) peer-reviewed publications remained. These post-mortem studies have provided data on DNA methylation, cellular and molecular alterations, and gene expression profiling in brain areas associated with OCD.

DISCUSSION AND CONCLUSION

Included studies highlight the potential value of post-mortem brains from well-characterized individuals with OCD and suggest the need for additional work in this area.

Clinical characteristics of probands with obsessive-compulsive disorder from simplex and multiplex families

Genetic and non-genetic factors contribute to obsessive-compulsive disorder (OCD), with strong evidence of familial clustering. Genomic studies in psychiatry have used the concepts of families that are "simplex" (one affected) versus "multiplex" (multiple affected). Our study compares demographic and clinical data from OCD probands in simplex and multiplex families to uncover potential differences. We analyzed 994 OCD probands (501 multiplex, 493 simplex) from the Brazilian Research Consortium on Obsessive-Compulsive Spectrum Disorders (C-TOC). Clinicians administered the Structured Clinical Interview for DSM-IV (SCID-IV) to diagnose, Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) to assess severity, and Dimensional Yale-Brown Obsessive-Compulsive Scale (DY-BOCS) to assess symptom dimensionality. Demographics, clinical history, and family data were collected. Compared to simplex probands, multiplex probands had earlier onset, higher sexual/religious and hoarding dimensions severity, increased comorbidity with other obsessive-compulsive-related disorders (OCRD), and higher family history of psychiatric disorders. These comparisons provide the first insights into demographic and clinical differences between Latin American simplex and multiplex families with OCD. Distinct clinical patterns may suggest diverse genetic and environmental influences. Further research is needed to clarify these differences, which have implications for symptom monitoring and management.

Chemical characterization and metabolic profiling of Xiao-Er-An-Shen Decoction by UPLC-QTOF/MS

Background: Xiao-Er-An-Shen decoction (XEASD), a TCM formula composed of sixteen Chinese medicinal herbs, has been used to alleviate tic disorders (TD) in clinical practice for many years. However, the chemical basis underlying the therapeutic effects of XEASD in the treatment of TD remains unknown. Purpose: The present study aimed to determine the major chemical components of XEASD and its prototype compounds and metabolites in mice biological samples. Methods: The chemical constituents in XEASD were identified using ultra-high Performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). Following this, XEASD was orally administered to mice, and samples of plasma, urine, feces, bile, and tissue were collected in order to identify effective compounds for the prevention or treatment of TD. Result: Of the total 184 compounds identified to be discriminated in the XEASD, comprising 44 flavonoids, 26 phenylpropanoids, 16 coumarins, 16 triterpenoids, 14 amino acids, 13 organic acids, 13 alkaloids, 13 ketones, 10 cyclic enol ether terpenes, 7 citrullines, 3 steroids, and 5 anthraquinones, and others. Furthermore, we summarized 54 prototype components and 78 metabolic products of XEASD, measured with biological samples, by estimating metabolic principal components, with four prototype compounds detected in plasma, 58 prototypes discriminated in urine, and 40 prototypes identified in feces. These results indicate that the Oroxylin A glucuronide from Citri reticulatae pericarpium (CRP) is a major compound with potential therapeutic effects identified in brain, while operating positive effect in inhibiting oxidative stress in vitro. Conclusion: In summary, our work delineates the chemical basis underlying the complexity of XEASD, providing insights into the therapeutic and metabolic pathways for TD. Various types of chemicals were explored in XEASD, including flavonoids, phenylpropanoids, coumarins, organic acids, triterpenoid saponins, and so on. This study can promote the further pharmacokinetic and pharmacological evaluation of XEASD.

The genetic epidemiology of obsessive-compulsive disorder: a systematic review and meta-analysis

The first systematic review and meta-analysis of obsessive-compulsive disorder (OCD) genetic epidemiology was published approximately 20 years ago. Considering the relevance of all the studies published since 2001, the current study aimed to update the state-of-art knowledge on the field. All published data concerning the genetic epidemiology of OCD from the CENTRAL, MEDLINE, EMBASE, BVS, and OpenGrey databases were searched by two independent researchers until September 30, 2021. To be included, the articles had to fulfill the following criteria: OCD diagnosis provided by standardized and validated instruments; or medical records; inclusion of a control group for comparison and case-control, cohort or twin study designs. The analysis units were the first-degree relatives (FDRs) of OCD or control probands and the co-twins in twin pairs. The outcomes of interest were the familial recurrence rates of OCD and the correlations of OCS in monozygotic compared with dizygotic twins. Nineteen family, twenty-nine twin, and six population-based studies were included. The main findings were that OCD is a prevalent and highly familial disorder, especially among the relatives of children and adolescent probands, that OCD has a phenotypic heritability of around 50%; and that the higher OCS correlations between MZ twins were mainly due to additive genetic or to non-shared environmental components.

Obsessive-Compulsive Disorder: Diagnosis, Clinical Features, Nosology, and Epidemiology

Obsessive-compulsive disorder (OCD) is characterized by time-consuming, distressing, or impairing obsessions and compulsions. Obsessions are recurrent, persistent, and intrusive thoughts, urges, or images. Compulsions are repetitive and often ritualized behaviors or mental acts performed to manage obsession-related distress or prevent harm. OCD affects 1% to 3% of the population, typically begins during adolescence or early adulthood, and can have a chronic or deteriorating course in the absence of effective treatment.

Latin American Trans-ancestry INitiative for OCD genomics (LATINO): Study Protocol

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder. Worldwide, its prevalence is ~2% and its etiology is mostly unknown. Identifying biological factors contributing to OCD will elucidate underlying mechanisms and might contribute to improved treatment outcomes. Genomic studies of OCD are beginning to reveal long-sought risk loci, but >95% of the cases currently in analysis are of homogenous European ancestry. If not addressed, this Eurocentric bias will result in OCD genomic findings being more accurate for individuals of European ancestry than other ancestries, thereby contributing to health disparities in potential future applications of genomics. In this study protocol paper, we describe the Latin American Trans-ancestry INitiative for OCD genomics (LATINO, www.latinostudy.org). LATINO is a new network of investigators from across Latin America, the United States, and Canada who have begun to collect DNA and clinical data from 5,000 richly-phenotyped OCD cases of Latin American ancestry in a culturally sensitive and ethical manner. In this project, we will utilize trans-ancestry genomic analyses to accelerate the identification of OCD risk loci, fine-map putative causal variants, and improve the performance of polygenic risk scores in diverse populations. We will also capitalize on rich clinical data to examine the genetics of treatment response, biologically plausible OCD subtypes, and symptom dimensions. Additionally, LATINO will help elucidate the diversity of the clinical presentations of OCD across cultures through various trainings developed and offered in collaboration with Latin American investigators. We believe this study will advance the important goal of global mental health discovery and equity.

Relationship between adverse childhood experiences and symptom severity in adult men with Tourette Syndrome

Childhood adversity is associated with the development or expression of many neuropsychiatric disorders, including those with strong genetic underpinnings. Despite reported associations between perceived stress and tic severity, the relationship between potentially traumatic events in childhood and Tourette Syndrome (TS), a highly heritable neuropsychiatric disorder, is unknown. This study aimed to assess whether exposure to eight categories of adverse childhood experiences (ACEs) is associated with TS severity and impairment, and whether TS genetic risk modifies this association. Online survey data were collected from 351 adult males with TS who previously participated in genetic studies. Participants completed the ACE questionnaire and a lifetime version of the Yale Global Tic Severity Scale (YGTSS). Demographic and relevant health data were assessed; polygenic risk scores (PRS) measuring aggregated TS genetic risk were derived using genome-wide association data. Univariable and multivariable linear regressions examined the relationships between childhood adversity and retrospectively recalled worst-ever tic severity and impairment, adjusting for covariates. Potential gene-by-environment (GxE) interactions between ACE and PRS were estimated. After covariate adjustment, there was a significant graded dose-response relationship between ACE Scores and increases in lifetime worst-ever tic severity and impairment. There was some evidence that TS genetic risk moderated the relationship between ACE Score and tic impairment, but not tic severity, particularly for individuals with higher TS polygenic risk. We provide evidence that childhood adversity is associated with higher lifetime TS severity and impairment, although future longitudinal studies with genetically-sensitive designs are needed to determine whether these relationships are causal and/or directional.

A prospective clinical cohort-based study of the prevalence of OCD, obsessive compulsive and related disorders, and tics in families of patients with OCD

BACKGROUND

The lifetime prevalence of obsessive - compulsive disorder (OCD) is currently estimated at 2 - 3% and the prevalence in first-degree family members is estimated to range between 10 and 11%. Separating OCD from other anxiety disorders and including it into the new "obsessive - compulsive and related disorders" (OCRDs) category has had a dramatic impact on the diagnosis, while also contributing to the better understanding of the genetics of these disorders. Indeed, grouping OCD with body dysmorphic disorder (BDD), and body-focused repetitive behaviors such as trichotillomania (hair pulling), onychophagia (nail biting), and excoriation (skin picking) into the same diagnostic family has resulted in a much greater lifetime prevalence (> 9%). These diagnostic changes necessitate an updated epidemiological study, thus motivating this investigation.

METHODS

The study sample comprised of 457 patient's cases from an Israeli and an Australian OCD center. Interviews were completed as a part of the intake or during treatment in each of the centers. Prevalence of OCD, OCRDs, tics, and other psychiatric comorbidities in first- and second-degree relatives was assessed by interviewing the OCD patients. Interviews were conducted by at least two researchers (LC, OBA, JZ) and only family information on which the interviewers have reached consensus was considered.

RESULTS

Initial analyses revealed an increase of OCD and OCRD prevalence in first- and second-degree family members as compared to the current literature due to reclassification of these disorders in DSM-5.

CONCLUSION

The new category of OCRD has changed the landscape of epidemiological studies in OCD. Further and broader studies are needed in order to better understand the lifetime prevalence of OCRD in first- and second-degrees family member.

Current Understanding of the Genetics of Tourette Syndrome

Gilles de la Tourette syndrome (TS) is a common, childhood-onset psychiatric disorder characterized by persistent motor and vocal tics. It is a heterogeneous disorder in which the phenotypic expression may be affected by environmental factors, such as immune responses. Furthermore, several studies have shown that genetic factors play a vital role in the etiology of TS, as well as its comorbidity with other disorders, including attention deficit hyperactivity disorder, obsessive-compulsive disorder, and autism spectrum disorder. TS has a complex inheritance pattern and, according to various genetic studies, several genes and loci have been correlated with TS. Genome-wide linkage studies have identified Slit and Trk-like 1 (SLITRK1) and histidine decarboxylase (HDC) genes, and candidate gene association studies have extensively investigated the dopamine and serotonin system genes, but there have been no consistent results. Moreover, genome-wide association studies have implicated several genetic loci; however, larger study cohorts are needed to confirm this. Copy number variations, which are polymorphisms in the number of gene copies due to chromosomal deletions or duplications, are considered another significant source of mutations in TS. In the last decade, whole genome/exome sequencing has identified several novel genetic mutations in patients with TS. In conclusion, more studies are needed to reveal the exact mechanisms of underlying TS, which may help to provide more information on the prognosis and therapeutic plans for TS.

A dimensional perspective on the genetics of obsessive-compulsive disorder

This review covers recent findings in the genomics of obsessive-compulsive disorder (OCD), obsessive-compulsive symptoms, and related traits from a dimensional perspective. We focus on discoveries stemming from technical and methodological advances of the past five years and present a synthesis of human genomics research on OCD. On balance, reviewed studies demonstrate that OCD is a dimensional trait with a highly polygenic architecture and genetic correlations to multiple, often comorbid psychiatric phenotypes. We discuss the phenotypic and genetic findings of these studies in the context of the dimensional framework, relying on a continuous phenotype definition, and contrast these observations with discoveries based on a categorical diagnostic framework, relying on a dichotomous case/control definition. Finally, we highlight gaps in knowledge and new directions for OCD genetics research.

Early onset obsessive-compulsive disorder: the biological and clinical phenotype

Moving from a behavioral-based to a biological-based classification of mental disorders is a crucial step toward a precision-medicine approach in psychiatry. In the last decade, a big effort has been made in order to stratify genetic, immunological, neurobiological, cognitive, and clinical profiles of patients. Making the case of obsessive-compulsive disorder (OCD), a lot have been made in this direction. Indeed, while the Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnosis of OCD aimed to delineate a homogeneous group of patients, it is now clear that OCD is instead an heterogeneous disorders both in terms of neural networks, immunological, genetic, and clinical profiles. In this view, a convergent amount of literature, in the last years, indicated that OCD patients with an early age at onset seem to have a specific clinical and biological profile, suggesting it as a neurodevelopmental disorder. Also, these patients tend to have a worse outcome respect to adult-onset patients and there is growing evidence that early-interventions could potentially improve their prognosis. Therefore, the aim of the present paper is to review the current available genetic, immunological, neurobiological, cognitive, and clinical data in favor of a more biologically precise subtype of OCD: the early-onset subtype. We also briefly resume current available recommendations for the clinical management of this specific population.

Whole genome analyses reveal significant convergence in obsessive-compulsive disorder between humans and dogs

Obsessive-compulsive disorder (OCD) represents a heterogeneous collection of diseases with diverse levels of phenotypic, genetic, and etiologic variability, making it difficult to identify the underlying genetic and biological mechanisms in humans. Domestic dogs exhibit several OCD-like behaviors. Using continuous circling as a representative phenotype for OCD, we screened two independent dog breeds, the Belgian Malinois and Kunming Dog and subsequently sequenced ten circling dogs and ten unaffected dogs for each breed. Using population differentiation analyses, we identified 11 candidate genes in the extreme tail of the differentiated regions between cases and controls. These genes overlap significantly with genes identified in a genome wide association study (GWAS) of human OCD, indicating strong convergence between humans and dogs. Through gene expressional analysis and functional exploration, we found that two candidate OCD risk genes, PPP2R2B and ADAMTSL3, affected the density and morphology of dendritic spines. Therefore, changes in dendritic spine may underlie some common biological and physiological pathways shared between humans and dogs. Our study revealed an unprecedented level of convergence in OCD shared between humans and dogs, and highlighted the importance of using domestic dogs as a model species for many human diseases including OCD.

Cutting-edge genetics in obsessive-compulsive disorder

This article reviews recent advances in the genetics of obsessive-compulsive disorder (OCD). We cover work on the following: genome-wide association studies, whole-exome sequencing studies, copy number variation studies, gene expression, polygenic risk scores, gene–environment interaction, experimental animal systems, human cell models, imaging genetics, pharmacogenetics, and studies of endophenotypes. Findings from this work underscore the notion that the genetic architecture of OCD is highly complex and shared with other neuropsychiatric disorders. Also, the latest evidence points to the participation of gene networks involved in synaptic transmission, neurodevelopment, and the immune and inflammatory systems in this disorder. We conclude by highlighting that further study of the genetic architecture of OCD, a great part of which remains to be elucidated, could benefit the development of diagnostic and therapeutic approaches based on the biological basis of the disorder. Studies to date revealed that OCD is not a simple homogeneous entity, but rather that the underlying biological pathways are variable and heterogenous. We can expect that translation from bench to bedside, through continuous effort and collaborative work, will ultimately transform our understanding of what causes OCD and thus how best to treat it.

Tourette syndrome research highlights from 2019

This is the sixth yearly article in the Tourette Syndrome Research Highlights series, summarizing research from 2019 relevant to Tourette syndrome and other tic disorders. The highlights from 2020 is being drafted on the Authorea online authoring platform; readers are encouraged to add references or give feedback on our selections comments feature on this page. After the calendar year ends, this article is submitted as the annual update for the Tics collection F1000Research.