Genetics of 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.

Identification of key mRNAs and signaling pathways in obsessive compulsive disorder based on weighted gene co-expression network analysis and cytoHubba plugin

PURPOSE

Obsessive-compulsive disorder (OCD) is a complex psychiatric disorder. Genetic and broad environmental factors are common risk factors for OCD. The purpose of this study is to explore the molecular mechanism of OCD and to find new molecular targets for the diagnosis and management of OCD.

METHODS

All data were downloaded from public dataset. Key modules and candidate key mRNAs were identified based on weighted gene co-expression network analysis (WGCNA). The "limma" R package was used for differential expression analysis of mRNAs. Subsequently, functional enrichment analysis of differentially expressed mRNAs (DEmRNAs) was also carried out. In addition, a diagnostic model was constructed. Finally, the infiltration level of immune cells in OCD and its correlation with multicentric key DEmRNAs were analyzed.

RESULTS

Green and red modules were selected as the hub modules. A total of 447 mRNAs were considered candidate key mRNAs according to GS > 0.2 and MM > 0.3. A total of 26 DEmRNAs in the same direction were identified in the GSE60190 and GSE78104 datasets. A total of 26 DEmRNAs were intersected with candidate key mRNAs in WGCNA to obtain 10 intersection DEmRNAs (HSPB1, ITPK1, CBX7, PPP1R10, TAOK1, PISD, MKNK2, RWDD1, PPA1, and RELN). However, only four DEmRNAs (HSPB1, TAOK1, MKNK2, and PPA1) predicted related drugs. Subsequently, receiver operating characteristic analysis shows that the diagnostic model has high diagnostic value. Moreover, six multicentric key DEmRNAs (SNRPF, SNRNP70, PRPF8, NOP56, EPRS, and CCT2) were screened by UpSet package. Finally, six multicentric key DEmRNAs were found to be associated with immune cells.

CONCLUSION

The key molecules obtained in this study lay a foundation for further research on the molecular mechanism of OCD.

When rare meets common: Treatable genetic diseases are enriched in the general psychiatric population

Mental illnesses are one of the biggest contributors to the global disease burden. Despite the increased recognition, diagnosis and ongoing research of mental health disorders, the etiology and underlying molecular mechanisms of these disorders are yet to be fully elucidated. Moreover, despite many treatment options available, a large subset of the psychiatric patient population is nonresponsive to standard medications and therapies. There has not been a comprehensive study to date examining the burden and impact of treatable genetic disorders (TGDs) that can present with neuropsychiatric features in psychiatric patient populations. In this study, we test the hypothesis that TGDs that present with psychiatric symptoms are more prevalent within psychiatric patient populations compared to the general population by performing targeted next-generation sequencing of 129 genes associated with 108 TGDs in a cohort of 2301 psychiatric patients. In total, 48 putative affected and 180 putative carriers for TGDs were identified, with known or likely pathogenic variants in 79 genes. Despite screening for only 108 genetic disorders, this study showed a two-fold (2.09%) enrichment for genetic disorders within the psychiatric population relative to the estimated 1% cumulative prevalence of all single gene disorders globally. This strongly suggests that the prevalence of these, and most likely all, genetic diseases is greatly underestimated in psychiatric populations. Increasing awareness and ensuring accurate diagnosis of TGDs will open new avenues to targeted treatment for a subset of psychiatric patients.

"Consumed by creed": Obsessive-compulsive symptoms underpin ideological obsession and support for political violence

Radicalization is a process by which individuals are introduced to an ideological belief system that encourages political, religious, or social change through the use of violence. Here we formulate an obsessive-compulsive disorder (OCD) model of radicalization that links obsessive passion (OP; one of the best predictors of radical intentions) to a larger body of clinical research. The model's central tenet is that individual differences in OCD symptom severity could shape radical intentions via their influence on OP. Across four ideological samples in the United States (Environmental activists, Republicans, Democrats, and Muslims, Ntotal  = 1114), we found direct effects between OCD symptom severity and radical intentions, as well as indirect effects of OCD on radical intentions via OP. Even after controlling for potential individual difference and clinical confounds (e.g., adverse childhood experiences, loss of significance, and substance abuse), these relationships remained robust, implying that OCD plays a significant role in the formation of violent ideological intentions and opening new avenues for the treatment and prevention of violent extremism. We discuss the implications of conceptualizing radicalization as an OCD-like disorder with compulsive violent tendencies and ideology-related concerns.

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.

Sex-dependent association of DNA methylation of HPA axis-related gene FKBP5 with obsessive-compulsive disorder

AIMS

Although hypothalamic-pituitary-adrenal (HPA) axis dysregulation in obsessive-compulsive disorder (OCD) has been reported, epigenetic changes in HPA axis-related genes have not been well studied in OCD. The present study investigated whether the epigenetic regulation of FK506-binding protein 51 gene (FKBP5) intron 7 is associated with OCD status in each sex. In addition, relationships among the DNA methylation levels of FKBP5 intron 7, OCD status and early-life trauma were explored.

METHODS

A total of 267 patients with OCD and 201 controls aged between 18 and 40 years were recruited. Demographic and clinical assessment, FKBP5 rs1360780 genotyping, and pyrosequencing of FKBP5 intron 7 were conducted. DNA was extracted from peripheral blood leucocytes. First, multivariate analysis of covariance for differential DNA methylation levels between OCD patients and controls was conducted with adjustment for FKBP5 rs1360780 genotype, early-life trauma, depressive symptoms, and age as covariates in each sex. Next, path analysis was conducted to determine the mediation effects of DNA methylation levels of FKBP5 between early-life trauma and OCD status. In addition, sensitivity analyses for medication and lifetime major depression were also performed.

RESULTS

DNA methylation at the FKBP5 intron 7 CpG site was significantly lower in men with OCD, compared to controls (mean difference -1.33%, 95% CI -2.11 to -0.55, p < 0.001). The results remained significant for drug naïve or free subjects (mean difference -1.27%, 95% CI -2.18 to -0.37, p = 0.006, in men) and for subjects without lifetime major depressive disorder (mean difference -1.60%, 95% CI -2.54 to -0.66, p < 0.001, in men). The mediation effect of DNA methylation levels was not significant between early-life trauma and OCD status.

CONCLUSION

These findings suggest that epigenetic factors of HPA axis-related gene FKBP5 may play a role in the pathogenesis of OCD. Further studies are needed to determine how altered DNA methylation of FKBP5 intron 7 and HPA axis function are involved in OCD.

Microbiome analysis of circulating bacterial extracellular vesicles in obsessive-compulsive disorder

AIM

The present study examined the microbiome abundance and composition of drug-naive or drug-free patients with obsessive-compulsive disorder (OCD) compared with healthy controls. In addition, in the OCD group, the microbiome composition was compared between early-onset and late-onset OCD.

METHODS

Serum samples were collected from 89 patients with OCD and 107 age- and sex-matched healthy controls. Bacterial DNA was isolated from bacteria-derived extracellular vesicles in serum and then amplified and quantified using primers specific to the V3-V4 hypervariable region of the 16S ribosomal RNA gene. The 16S ribosomal DNA gene amplicon sequencing was performed.

RESULTS

The pooled estimate showed that α-diversity was significantly reduced in patients with OCD compared with that in healthy controls (PShannon  = 0.00015). In addition, a statistically significant difference was observed in β-diversity between patients with OCD and healthy controls at the order (P = 0.012), family (P = 0.003), genus (P < 0.001), and species (P = 0.005) levels. In the microbiome composition, Pseudomonas, Caulobacteraceae (f), Streptococcus, Novosphingobium, and Enhydrobacter at the genus level were significantly less prevalent in patients with OCD than in controls. In addition, among patients with OCD, the microbial composition in the early-onset versus late-onset types was significantly different with respect to the genera Corynebacterium and Pelomonas.

CONCLUSION

The present study showed an aberrant microbiome in patients with OCD, suggesting a role of the microbiota-brain interaction in the pathophysiology of OCD. Further longitudinal studies with larger sample sizes adjusting for various confounders are warranted.

Association of granulocyte macrophage colony-stimulating factor and interleukin-17 levels with obsessive-compulsive disorder: a case-control study findings

Obsessive-compulsive disorder (OCD) is a mental condition that affects many people and is characterized by recurring obsessions and compulsions. It significantly impacts individuals' ability to function ordinarily daily, affecting people of all ages. This study aimed to investigate whether or not the cytokines granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin-17 (IL-17) are involved in the pathophysiology of OCD. A case-control study with 50 OCD patients and 38 healthy volunteers served as the controls for this investigation. The levels of GM-CSF and IL-17 in the serum of both groups were measured with enzyme-linked immunosorbent assay (ELISA) kits. In addition, the sociodemographic characteristics of the population under study were studied. Based on the findings of this study, OCD patients had significantly elevated levels of IL-17 than the controls, it appears that there may be a function for IL-17 in the pathophysiology of OCD. It was also discovered that the severity of OCD and IL-17 levels had a significant positive correlation. On the other hand, when comparing the levels of GM-CSF, there was no significant difference between the patients and the controls. This study provides evidence supporting the involvement of cytokine IL-17 in the pathophysiology of OCD. This study suggests IL-17 as a diagnostic biomarker for OCD and adds to our knowledge of the function that the immune system plays in this condition.

Socioeconomic resources moderate the relationship between maternal prenatal obsessive-compulsive symptoms and infant negative affectivity

Perinatal maternal depression, anxiety, and stress are associated with poor infant outcomes. However, no known study has investigated the effects of perinatal maternal obsessive-compulsive symptomatology on infant outcomes while considering important situational factors such as socioeconomic resources. Therefore, we investigated the effects of prenatal and postnatal obsessive-compulsive symptomatology on infant behavioral reactivity, beyond the effects of postnatal depressive symptomatology, at 6 months of age. It was expected that socioeconomic resources would moderate this relationship. We recruited 125 pregnant women from a Health Professional Shortage Area for mental health and primary care in the Midwest United States and interviewed them at approximately 34 weeks gestation and again at 6 months postnatally. They were administered questionnaires at both time points measuring obsessive-compulsive and depressive symptoms. Infant behavioral reactivity was gathered during 6-month follow-up through behavioral observation coding and maternal-report modalities. Maternal-reported infant negative affectivity at 6 months was related to greater severity of maternal postnatal depressive symptomatology, and socioeconomic resources moderated the relationship between maternal prenatal obsessive-compulsive symptoms and maternal-reported infant negative affectivity. However, neither of these relations was statistically significant when infant reactivity was quantified using behavioral observations.

The shared genetic risk factors between Tourette syndrome and obsessive-compulsive disorder

Tourette syndrome (TS) and obsessive-compulsive disorder (OCD) are two neuropsychiatric disorders that frequently co-occur. Previous evidence suggests a shared genetic diathesis underlying the comorbidity of TS and OCD. This review aims to comprehensively summarize the current literature on the genetic factors linked with TS and its comorbidities, with a focus on OCD. Family studies, linkage analysis, cytogenetic studies, and genome-wide association studies (GWAS) have played a pivotal role in identifying common and rare genetic variants connected with TS and OCD. Although the genetic framework of TS and OCD is complex and multifactorial, several susceptibility loci and candidate genes have been identified that might play a crucial role in the pathogenesis of both disorders. Additionally, post-infectious environmental elements have also been proposed to contribute to the development of TS-OCD, although the dynamics between genetic and environmental factors is not yet fully understood. International collaborations and studies with well-defined phenotypes will be crucial in the future to further elucidate the genetic basis of TS and OCD and to develop targeted therapeutic strategies for individuals suffering from these debilitating conditions.

Epigenome-wide analysis identifies methylome profiles linked to obsessive-compulsive disorder, disease severity, and treatment response

Obsessive-compulsive disorder (OCD) is a prevalent mental disorder affecting ~2-3% of the population. This disorder involves genetic and, possibly, epigenetic risk factors. The dynamic nature of epigenetics also presents a promising avenue for identifying biomarkers associated with symptom severity, clinical progression, and treatment response in OCD. We, therefore, conducted a comprehensive case-control investigation using Illumina MethylationEPIC BeadChip, encompassing 185 OCD patients and 199 controls recruited from two distinct sites in Germany. Rigorous clinical assessments were performed by trained raters employing the Structured Clinical Interview for DSM-IV (SCID-I). We performed a robust two-step epigenome-wide association study that led to the identification of 305 differentially methylated CpG positions. Next, we validated these findings by pinpointing the optimal set of CpGs that could effectively classify individuals into their respective groups. This approach identified a subset comprising 12 CpGs that overlapped with the 305 CpGs identified in our EWAS. These 12 CpGs are close to or in genes associated with the sweet-compulsive brain hypothesis which proposes that aberrant dopaminergic transmission in the striatum may impair insulin signaling sensitivity among OCD patients. We replicated three of the 12 CpGs signals from a recent independent study conducted on the Han Chinese population, underscoring also the cross-cultural relevance of our findings. In conclusion, our study further supports the involvement of epigenetic mechanisms in the pathogenesis of OCD. By elucidating the underlying molecular alterations associated with OCD, our study contributes to advancing our understanding of this complex disorder and may ultimately improve clinical outcomes for affected individuals.

Treatment in Children and Adolescents With Obsessive-Compulsive Disorder: Review for Practitioners

Obsessive-compulsive disorder (OCD) is one of the most debilitating mental health conditions, interrupting functioning at school and social well-being in children and adolescents. Youth tend to delay interventions and when sought, response to treatment might not be optimal. The current article discusses treatment guidelines for youth with OCD and pediatric autoimmune neuropsychiatric symptoms. [Journal of Psychosocial Nursing and Mental Health Services, 61(8), 11-15.].

Microbial Reprogramming in Obsessive-Compulsive Disorders: A Review of Gut-Brain Communication and Emerging Evidence

Obsessive-compulsive disorder (OCD) is a debilitating mental health disorder characterized by intrusive thoughts (obsessions) and repetitive behaviors (compulsions). Dysbiosis, an imbalance in the gut microbial composition, has been associated with various health conditions, including mental health disorders, autism, and inflammatory diseases. While the exact mechanisms underlying OCD remain unclear, this review presents a growing body of evidence suggesting a potential link between dysbiosis and the multifaceted etiology of OCD, interacting with genetic, neurobiological, immunological, and environmental factors. This review highlights the emerging evidence implicating the gut microbiota in the pathophysiology of OCD and its potential as a target for novel therapeutic approaches. We propose a model that positions dysbiosis as the central unifying element in the neurochemical, immunological, genetic, and environmental factors leading to OCD. The potential and challenges of microbial reprogramming strategies, such as probiotics and fecal transplants in OCD therapeutics, are discussed. This review raises awareness of the importance of adopting a holistic approach that considers the interplay between the gut and the brain to develop interventions that account for the multifaceted nature of OCD and contribute to the advancement of more personalized approaches.

Relationship between gene-environment interaction and obsessive-compulsive disorder: A systematic review

BACKGROUND

Gene-environment interaction (G × E) refers to the change of genetic effects under the participation of environmental factors resulting in differences in genetic expression. G × E has been studied in the occurrence and development of many neuropsychiatric disorders, including obsessive-compulsive disorder (OCD).

AIM

A systematic review was conducted to investigate the role of G × E plays in OCD. This review explored the relationship between G × E and the susceptibility to OCD occurrence, disease progression, and treatment response.

METHODS

This systematic literature search was performed using Web of Science, PubMed, Cochrane Library, and CNKI. Seven studies were selected, which included seven genes (BDNF, COMT, MAO, 5-HTT, SMAD4, PGRN, and SLC1A1) polymorphisms, polygenic risk score (PRS), and two environmental factors (childhood trauma and stressful life events).

RESULTS

Information from this systematic review indicated that G × E increased the susceptibility to OCD, played a crucial role in the clinical characteristics, and had an inconsistent impact on treatment response of OCD.

FUTURE DIRECTIONS

The multi-omics studies and the inclusion of G × E in future GWAS studies of OCD should be drawn more attention, which may contribute to a deeper understanding of the etiology of OCD as well as guide therapeutic interventions for the disease.

Epigenetics in psychiatry: Beyond DNA methylation

The global burden of psychopathologies appears to be underestimated, since the global psychiatric disorder burden is exceeding other medical burdens. To be able to address this problem more effectively, we need to better understand the etiology of psychiatric disorders. One of the hallmarks of psychiatric disorders appears to be epigenetic dysregulation. While some epigenetic modifications (such as DNA methylation) are well known and studied, the roles of others have been investigated much less. DNA hydroxymethylation is a rarely studied epigenetic modification, which as well as being an intermediate stage in the DNA demethylation cycle is also an independent steady cell state involved in neurodevelopment and plasticity. In contrast to DNA methylation, DNA hydroxymethylation appears to be related to an increase in gene expression and subsequent protein expression. Although no particular gene or genetic locus can be at this point linked to changes in DNA hydroxymethylation in psychiatric disorders, the epigenetic marks present good potential for biomarker identification because the epigenetic landscape is a result of the interplay between genes and environment, which both influence the development of psychiatric disorders, and because hydoxymethylation changes are particularly enriched in the brain and in synapse-related genes.

Mapping the neuroanatomical heterogeneity of OCD using a framework integrating normative model and non-negative matrix factorization

Obsessive-compulsive disorder (OCD) is a spectrum disorder with high interindividual heterogeneity. We propose a comprehensible framework integrating normative model and non-negative matrix factorization (NMF) to quantitatively estimate the neuroanatomical heterogeneity of OCD from a dimensional perspective. T1-weighted magnetic resonance images of 98 first-episode untreated patients with OCD and matched healthy controls (HCs, n = 130) were acquired. We derived individualized differences in gray matter morphometry using normative model and parsed them into latent disease factors using NMF. Four robust disease factors were identified. Each patient expressed multiple factors and exhibited a unique factor composition. Factor compositions of patients were significantly correlated with severity of symptom, age of onset, illness duration, and exhibited sex differences, capturing sources of clinical heterogeneity. In addition, the group-level morphological differences obtained with two-sample t test could be quantitatively derived from the identified disease factors, reconciling the group-level and subject-level findings in neuroimaging studies. Finally, we uncovered two distinct subtypes with opposite morphological differences compared with HCs from factor compositions. Our findings suggest that morphological differences of individuals with OCD are the unique combination of distinct neuroanatomical patterns. The proposed framework quantitatively estimating neuroanatomical heterogeneity paves the way for precision medicine in OCD.

Obsessive-Compulsive Disorder and Its Cross-Generational Familial Association With Anxiety Disorders in a National Swedish Extended Adoption Study

Importance

We know little about the transmission of obsessive-compulsive disorder (OCD) across generations.

Objective

To evaluate the sources of parent-offspring transmission of OCD and familial cross-generational association with more typical anxiety disorders.

Design, Setting, and Participants

This Swedish population register-based study analyzed data for offspring born in Sweden from 1960 to 1995 from the following 4 family types: intact, not-lived-with biological father, lived-with stepfather, and adoptive. Follow-up occurred on December 31, 2018, and data were analyzed from April 6, 2022, to September 26, 2022.

Exposures

Three sources of parent-offspring resemblance: genes plus rearing, genes only, and rearing only.

Main Outcomes and Measures

Diagnoses of OCD, all anxiety disorders, generalized anxiety disorder (GAD), social phobia, and panic disorder were obtained from national inpatient, outpatient, and primary care medical registers. Parent-child resemblance was assessed by tetrachoric correlation (r).

Results

The offspring population consisted of 2 413 128 individuals; mean (SD) age at follow-up was 40.2 (10.7) years, 1 258 670 individuals (52.2%) were male, and 1 154 458 individuals (47.8%) were female. For each type of parent-child relationship, the best-estimate correlation for OCD for genes plus rearing was 0.19 (95% CI, 0.17 to 0.20); genes only, 0.18 (95% CI, 0.11 to 0.24); and rearing only, 0.04 (95% CI, -0.10 to 0.19). From bivariate adoption analyses, the cross-generational genetic correlations between OCD with anxiety disorder diagnostic categories were estimated as follows: for all anxiety disorders, 0.62 (95% CI, 0.46 to 0.77); GAD, 0.87 (95% CI, 0.53 to 1.00); social phobia, 0.70 (95% CI, 0.31 to 1.00); and panic disorder, 0.47 (95% CI, 0.20 to 0.73).

Conclusions and Relevance

This Swedish population register-based study found that OCD was transmitted from parents to children largely through a genetic relationship, with rearing playing a minor role. Viewed cross-generationally, OCD and anxiety disorders were moderately genetically correlated, with the genetic correlations strongest between OCD and GAD, intermediate for OCD and social phobia, and weakest between OCD and panic disorder. These genetic correlations were modestly attenuated when diagnostic hierarchies were imposed before analysis.

Beyond monoamines: I. Novel targets and radiotracers for Positron emission tomography imaging in psychiatric disorders

With the emergence of positron emission tomography (PET) in the late 1970s, psychiatry had access to a tool capable of non-invasive assessment of human brain function. Early applications in psychiatry focused on identifying characteristic brain blood flow and metabolic derangements using radiotracers such as [¹⁵ O]H₂ O and [¹⁸ F]FDG. Despite the success of these techniques, it became apparent that more specific probes were needed to understand the neurochemical bases of psychiatric disorders. The first neurochemical PET imaging probes targeted sites of action of neuroleptic (dopamine D₂ receptors) and psychoactive (serotonin receptors) drugs. Based on the centrality of monoamine dysfunction in psychiatric disorders and the measured success of monoamine-enhancing drugs in treating them, the next 30 years witnessed the development of an armamentarium of PET radiopharmaceuticals and imaging methodologies for studying monoamines. Continued development of monoamine-enhancing drugs over this time however was less successful, realizing only modest gains in efficacy and tolerability. As patent protection for many widely prescribed and profitable psychiatric drugs lapsed, drug development pipelines shifted away from monoamines in search of novel targets with the promises of improved efficacy, or abandoned altogether. Over this period, PET radiopharmaceutical development activities closely paralleled drug development priorities resulting in the development of new PET imaging agents for non-monoamine targets. Part one of this review will briefly survey novel PET imaging targets with relevance to the field of psychiatry, which include the metabotropic glutamate receptor type 5 (mGluR5), purinergic P₂ X₇ receptor, type 1 cannabinoid receptor (CB₁ ), phosphodiesterase 10A (PDE10A), and describe radiotracers developed for these and other targets that have matured to human subject investigations. Current limitations of the targets and techniques will also be discussed.

Correlations between single nucleotide polymorphisms in obsessive-compulsive disorder with the clinical features or response to therapy

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric disorder, in which the patient endures intrusive thoughts or is compelled to perform repetitive or ritualized actions. Many cases of OCD are considered to be familial or heritable in nature. It has been shown that a variety of internal and external risk factors are involved in the pathogenesis of OCD. Among the internal factors, genetic modifications play a critical role in the pathophysiological process. Despite many investigations performed to determine the candidate genes, the precise genetic factors involved in the disease remain largely undetermined. The present review summarizes the single nucleotide polymorphisms that have been proposed to be associated with OCD symptoms, early onset disease, neuroimaging results, and response to therapy. This information could help us to draw connections between genetics and OCD symptoms, better characterize OCD in individual patients, understand OCD prognosis, and design more targeted personalized treatment approaches.

Obsessive-compulsive symptoms in ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome

Symptoms of obsessive–compulsive disorder (OCD) may rarely occur in the context of genetic syndromes. So far, an association between obsessive–compulsive symptoms (OCS) and ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome has not been described as yet. A thoroughly phenotyped patient with OCS and ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome is presented. The 25-year-old male patient was admitted to in-patient psychiatric care due to OCD. A whole-exome sequencing analysis was initiated as the patient also showed an autistic personality structure, below average intelligence measures, craniofacial dysmorphia signs, sensorineural hearing loss, and sinus cavernoma as well as subtle cardiac and ophthalmological alterations. The diagnosis of Baraitser-Winter cerebrofrontofacial syndrome type 2 was confirmed by the detection of a heterozygous likely pathogenic variant in the ACTG1 gene [c.1003C > T; p.(Arg335Cys), ACMG class 4]. The automated analysis of magnetic resonance imaging (MRI) revealed changes in the orbitofrontal, parietal, and occipital cortex of both sides and in the right mesiotemporal cortex. Electroencephalography (EEG) revealed intermittent rhythmic delta activity in the occipital and right temporal areas. Right mesiotemporal MRI and EEG alterations could be caused by a small brain parenchymal defect with hemosiderin deposits after a cavernomectomy. This paradigmatic case provides evidence of syndromic OCS in ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome. The MRI findings are compatible with a dysfunction of the cortico-striato-thalamo-cortical loops involved in OCD. If a common pathophysiology is confirmed in future studies, corresponding patients with Baraitser-Winter cerebrofrontofacial syndrome type 2 should be screened for OCS. The association may also contribute to a better understanding of OCD pathophysiology.

Phenotypic Impact of Rare Potentially Damaging Copy Number Variation in Obsessive-Compulsive Disorder and Chronic Tic Disorders

BACKGROUND

Recent studies report an important-and previously underestimated-role of rare variation in risk of obsessive-compulsive disorder (OCD) and chronic tic disorders (CTD). Using data from a large epidemiological study, we evaluate the distribution of potentially damaging copy number variation (pdCNV) in OCD and CTD, examining associations between pdCNV and the phenotypes of probands, including a consideration of early- vs. late-diagnoses.

METHOD

The Obsessive-Compulsive Inventory-Revised (OCI-R) questionnaire was used to ascertain psychometric profiles of OCD probands. CNV were identified genome-wide using chromosomal microarray data.

RESULTS

For 993 OCD cases, 86 (9%) were identified as pdCNV carriers. The most frequent pdCNV found was at the 16p13.11 region. There was no significant association between pdCNV and the OCI-R total score. However, pdCNV was associated with Obsessing and Checking subscores. There was no significant difference in pdCNV frequency between early- vs. late-diagnosed OCD probands. Of the 217 CTD cases, 18 (8%) were identified as pdCNV carriers. CTD probands with pdCNV were significantly more likely to have co-occurring autism spectrum disorder (ASD).

CONCLUSIONS

pdCNV represents part of the risk architecture for OCD and CTD. If replicated, our findings suggest pdCNV impact some OCD symptoms. Genes within the 16p13.11 region are potential OCD risk genes.

Morbidity and mortality in obsessive-compulsive disorder: A narrative review

Current knowledge on the general somatic health of individuals with obsessive-compulsive disorder (OCD) is very limited. Here, we critically review the emerging literature on the topic. Rapidly accumulating evidence indicates an association between OCD and autoimmune diseases, which is not limited to streptococcus-related conditions. Similarly, an association with metabolic and circulatory system diseases has been reported, which is at least partially independent from psychiatric comorbidities and familial confounders. Preliminary results also suggest potential links with dementia, insomnia, respiratory diseases, gastrointestinal diseases, migraine, and chronic pain, but replication is warranted. The risk of death by suicide in OCD is now well established. OCD has also been associated to increased mortality due to natural causes, but more research on specific causes of death is needed. Clarification of the mechanisms behind the observed associations will be critical to inform the rational design of prevention efforts. In the meantime, while OCD symptom reduction remains a priority, clinicians should also focus on monitoring the general health and promoting healthy lifestyles of persons with OCD.

Co-occurring OCD and Panic Disorder: A Review of Their Etiology and Treatment

Estimated rates of co-occurrence between obsessive and compulsive disorder (OCD) and panic disorder (PD) are notable, but vary considerably, with rates from epidemiological and clinical studies ranging from 1.8% to 22% (Rector et al., 2017). We reviewed the current empirical literature on the etiology, treatment, diagnostic assessment, and differential diagnosis of co-occurring OCD/PD. Best practices for cognitive-behavioral treatment, including identifying and addressing treatment barriers are also addressed. Although it is acknowledged in current literature that co-occurring OCD and PD levels may be clinically significant, there remains a need to thoroughly examine the possible consequences and future research directions of this overlap. Future research must continue to elucidate the biological and environmental causes of OCD/PD co-occurrence.

The Genetic Architecture of Obsessive-Compulsive Disorder: Contribution of Liability to OCD From Alleles Across the Frequency Spectrum

OBJECTIVE

Obsessive-compulsive disorder (OCD) is known to be substantially heritable; however, the contribution of genetic variation across the allele frequency spectrum to this heritability remains uncertain. The authors used two new homogeneous cohorts to estimate the heritability of OCD from inherited genetic variation and contrasted the results with those of previous studies.

METHODS

The sample consisted of 2,090 Swedish-born individuals diagnosed with OCD and 4,567 control subjects, all genotyped for common genetic variants, specifically >400,000 single-nucleotide polymorphisms (SNPs) with minor allele frequency (MAF) ≥0.01. Using genotypes of these SNPs to estimate distant familial relationships among individuals, the authors estimated the heritability of OCD, both overall and partitioned according to MAF bins.

RESULTS

Narrow-sense heritability of OCD was estimated at 29% (SE=4%). The estimate was robust, varying only modestly under different models. Contrary to an earlier study, however, SNPs with MAF between 0.01 and 0.05 accounted for 10% of heritability, and estimated heritability per MAF bin roughly followed expectations based on a simple model for SNP-based heritability.

CONCLUSIONS

These results indicate that common inherited risk variation (MAF ≥0.01) accounts for most of the heritable variation in OCD. SNPs with low MAF contribute meaningfully to the heritability of OCD, and the results are consistent with expectation under the "infinitesimal model" (also referred to as the "polygenic model"), where risk is influenced by a large number of loci across the genome and across MAF bins.

Symptom provocation in obsessive-compulsive disorder: A voxel-based meta-analysis and meta-analytic connectivity modeling

BACKGROUND

Obsessive-compulsive disorder (OCD) is a heterogeneous psychiatric illness with a complex array of symptoms and potentially distinct neural underpinnings. We employed meta-analysis and connectivity modeling of symptom dimensions to delineate the circuit mechanisms of OCD.

METHODS

With the activation likelihood estimation (ALE) algorithm we performed meta-analysis of whole-brain functional magnetic resonance imaging (fMRI) studies of symptom provocation. We contrasted all OCD patients and controls in a primary analysis and divided the studies according to clinical symptoms in secondary meta-analyses. Finally, we employed meta-analytic connectivity modeling analyses (MACMs) to examine co-activation patterns of the brain regions revealed in the primary meta-analysis.

RESULTS

A total of 14 experiments from 12 eligible studies with a total of 238 OCD patients (124 men) and 219 healthy controls (120 men) were included in the primary analysis. OCD patients showed higher activation in the right caudate body/putamen/insula and lower activation in the left orbitofrontal cortex (OFC), left inferior frontal gyrus (IFG), left caudate body/middle cingulate cortex (MCC), right middle temporal gyrus (MTG), middle occipital gyrus (MOG) and right lateral occipital gyrus (LOG). MACMs revealed significant co-activation between left IFG and left caudate body/MCC, left MOG and right LOG, right LOG and MTG. In the secondary meta-analyses, the washing subgroup showed higher activation in the right OFC, bilateral ACC, left MOG and right caudate body.

CONCLUSION

OCD patients showed elevated dorsal striatal activation during symptom provocation. In contrast, the washing subgroup engaged higher activation in frontal, temporal and posterior cortical structures as well as right caudate body. Broadly consistent with the proposition of cortico-striatal-thalamic-cortical circuit dysfunction, these findings highlight potentially distinct neural circuits that may underlie the symptoms and potentially etiological subtypes of OCD.

Tourettic OCD: Current understanding and treatment challenges of a unique endophenotype

Obsessive compulsive disorder (OCD) and chronic tic disorders (CTD) including Tourette Syndrome (TS) are often comorbid conditions. While some patients present with distinct symptoms of CTD and/or OCD, a subset of patients demonstrate a unique overlap of symptoms, known as Tourettic OCD (TOCD), in which tics, compulsions, and their preceding premonitory urges are overlapping and tightly intertwined. The specific behaviors seen in TOCD are typically complex tic-like behaviors although with a compulsive and partially anxious nature reminiscent of OCD. TOCD is not classified within the Diagnostic and Statistical Manual of Mental Disorders fifth edition (DSM-5) as an independent diagnostic entity, but mounting evidence suggests that TOCD is an intermediate neuropsychiatric disorder distinct from either TS or OCD alone and as such represents a unique phenomenology. In this review of TOCD we discuss clinical, genetic, environmental, neurodevelopmental, and neurocircuit-based research to better characterize our current understanding of this disorder. TOCD is characterized by earlier age of onset, male predominance, and specific symptom clusters such as lower tendency toward compulsions related to checking, cleaning, and reassurance seeking and higher tendency toward compulsions such as rubbing, tapping, or touching associated with symmetry concerns or thoughts of exactness. Functional magnetic resonance imaging (fMRI) imaging suggests that TOCD symptoms may arise from involvement of an intermediate neurocircuitry distinct from classic OCD or classic CTD. Small cumulative contributions from multiple genetic loci have been implicated, as have environmental factors such as infection and perinatal trauma. In addition, this review addresses the treatment of TOCD which is especially complex and often treatment resistant and requires pharmacology and behavioral therapy in multiple modalities. Given the distressing impact of TOCD on patients' functioning, the goal of this review is to raise awareness of this distinct entity toward the goal of improving standards of care.

Psilocybin for the Treatment of Obsessive-Compulsive Disorders

Obsessive-compulsive disorder (OCD) is a highly prevalent and disabling condition for which currently available treatments are insufficiently effective and alternatives merit priority attention. Psilocybin may represent a safe and effective avenue for treatment of individuals affected by this condition. In this chapter we briefly introduce OCD symptoms, epidemiology, as well as relevant hypotheses on the mechanism of disease that may inform treatment interventions. We briefly describe currently available treatments, mechanisms of action, and efficacy limitations, as preamble to the potential use of psilocybin and perhaps similar compounds in the treatment of OCD and related conditions. Although much is reviewed throughout this book about the mechanisms of action of psychedelic agents, a focused discussion of psilocybin effects as they pertain to OCD is also included. Our experience with incidental observation, prospective research, and current explorations of psilocybin in OCD are also described.

What Have We Learned About the Genetics of Obsessive-Compulsive and Related Disorders in Recent Years?

Obsessive-compulsive disorder (OCD) is a complex, multifactorial disorder with onset in either childhood or early adulthood. Lifetime prevalence has been estimated to be around 2%-3%. DSM-5 groups OCD together with closely related disorders-body dysmorphic disorder, trichotillomania (hair-pulling disorder), hoarding disorder, and excoriation disorder (skin-picking disorder)-as obsessive-compulsive and related disorders (OCRDs). In addition, DSM-5 includes a "tic-related" specifier, recognizing that OCD and Tourette syndrome/chronic tics are frequently comorbid. In recent years, the first large-scale genome-wide studies of OCRDs have emerged. These studies confirmed results from earlier twin and family studies that have demonstrated a strong genetic component to OCRDs. Furthermore, from analyses of common genetic variation, these studies offered a first insight into how the genetic risk of developing an OCRD might be connected to the genetic risk of developing another OCRD. This article is an update of the authors' previous report; it summarizes recent findings on the genetics of OCRDs and highlights some of the recent directions in OCRD genetics that will pave the way for new insights into OCRD pathophysiology.