Obsessive-Compulsive Disorder: Autoimmunity and Neuroinflammation

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.

Informational Analysis and Prediction of Obsessive-Compulsive Disorder Pathogenesis

OBJECTIVE

We aimed to predict the possible mechanism of obsessive-compulsive disorder (OCD) by integrating and analyzing mRNA sequencing results from two datasets and to provide direction for future studies into the pathogenesis of OCD.

METHODS

Two OCD datasets, GSE78104 and GSE60190, were obtained, and the intersection of the two gene sets with differential expression in OCD samples was selected. Kyoto Encyclopedia of Genes and Genomes (KEGG) signal pathway enrichment and Gene Ontology (GO) analyses were performed using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) online analysis website for the genes at the intersection, and the data were mapped using http://www.bioinformatics.com.cn. After genes with p≤0.05 had been screened out, protein-protein interaction (PPI) interaction analysis was conducted using Metascape to screen the key Molecular Complex Detection (MCODE) genes. MCODE genes were then enriched using the KEGG signaling pathway and GO classification.

RESULTS

A total of 3,449 differentially expressed genes (DEGs) were obtained from the GSE78104 and GSE60190 datasets. KEGG, GO, and Gene Set Enrichment Analysis analyses of DEGs showed that the onset of OCD was related to oxidative phosphorylation and other metabolic processes, which may have a similar pathogenesis to other neurodegenerative diseases. Single-gene PPI analysis of SAPAP3 revealed that the mechanism by which SAPAP3 knockout induces OCD may also be caused by affecting oxidative phosphorylation.

CONCLUSION

The mechanism of SAPAP3 knockout-induced OCD in mice may be due to the oxidative phosphorylation process in the body. Future studies on the neural circuit mechanism of OCD should be conducted.

Potential biomarkers and therapeutic targets for obsessive compulsive disorder: Evidences from clinical studies

Obsessive compulsive disorder (OCD) is a prevalent behavioral disorder with a complex etiology. However, the underlying pathogenic molecular pathways and the associated risk factors are largely obscure. This has hindered both the identification of relevant prognostic biomarkers and the development of effective treatment strategies. Because of the diverse range of clinical manifestations, not all patients benefit from therapies currently practiced in the clinical setting. Nevertheless, several lines of evidence indicate that neurotrophic, neurotransmitter, and oxidative signaling are involved in the pathophysiology of OCD. Based upon evidences from clinical (and pre-clinical studies), the present review paper sets out to decipher the utilities of three parameters (i.e. brain-derived neurotrophic factor; BDNF, noradrenalin-synthesizing enzyme dopamine beta-hydroxylase; DBH; and oxidative damage marker malondialdehyde; MDA) as diagnostic peripheral biomarkers as well as bio-targets for therapeutic strategies. While the data indicates promising results, there is necessitation for future studies to further confirm and establish these. Further, based again on the available clinical data, we investigated the possibilities of exploiting the etiological links between disruptions in the sleep-wake cycle and insulin signaling, and OCD for the identification of potential anti-OCD ameliorative agents with the ability to elicit multimodal effects, including attenuation of the alterations in BDNF, noradrenergic and redox pathways. In this respect, agomelatine and metformin may represent particularly interesting candidates; however, further clinical studies are warranted to establish these as singular or complementary medications in OCD subjects.

Targeting inflammatory signaling in obsessive compulsive disorder: a promising approach

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder. Approximately, around 2% to 3% percent of the general population experience symptoms of OCD over the course of their lifetime. OCD can lead to economic burden, poor quality of life, and disability. The characteristic features exhibited generally in OCD are continuous intrusive thoughts and periodic ritualized behaviours. Variations in genes, pathological function of Cortico-Striato-Thalamo-Cortical (CSTC) circuits and dysregulation in the synaptic conduction have been the major factors involved in the pathological progression of OCD. However, the basic mechanisms still largely unknown. Current therapies for OCD largely target monoaminergic neurotransmitters (NTs) in specific dopaminergic and serotonergic circuits. However, such therapies have limited efficacy and tolerability. Drug resistance has been one of the important reasons reported to critically influence the effectiveness of the available drugs. Inflammation has been a crucial factor which is believed to have a significant importance in OCD progression. A significant number of proinflammatory cytokines have been reportedly amplified in patients with OCD. Mechanisms of drug treatment involve attenuation of the symptoms via modulation of inflammatory signalling pathways, modification in brain structure, and synaptic plasticity. Hence, targeting inflammatory signaling may be considered as a suitable approach in the treatment of OCD. The present review focuses mainly on the significant findings from the animal and human studies conducted in this area, that targets inflammatory signaling in neurological conditions. In addition, it also focusses on the therapeutic approaches that target OCD via modification of the inflammatory signaling pathways.

Cerebrospinal fluid findings in patients with obsessive-compulsive disorder, Tourette syndrome, and PANDAS: A systematic literature review

BACKGROUND

Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are related mental disorders that share genetic, neurobiological, and phenomenological features. Pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS) is a neuropsychiatric autoimmune disorder with symptoms of OCD and/or TS associated with streptococcal infections. Therefore, PANDAS represents a strong link between OCD, TS, and autoimmunity. Notably, cerebrospinal fluid (CSF) analyses can provide insight into the central nervous processes in OCD, TS, and PANDAS.

METHODS

A systematic literature search according to the PRISMA criteria was conducted to collect all CSF studies in patients with OCD, TS, and PANDAS. The total number of cases and the heterogeneity of the low number of studies were not sufficient for a meta-analysis to provide a high level of evidence. Nevertheless, meta-analytical statistics could be performed for glutamate, 5-hydroxyindoleacetic acid (degradation product of serotonin), homovanillic acid (degradation product of dopamine), 3-methoxy-4-hydroxyphenylglycol (major metabolite of noradrenaline), and corticotropin-releasing hormone (CRH) in OCD. A risk-of-bias assessment was implemented using the Cochrane ROBINS-E tool.

RESULTS

Meta-analytical testing identified elevated glutamate levels in the CSF of OCD patients compared with healthy controls, while no significant differences were found in other neurotransmitters or CRH. Single studies detected novel neuronal antibodies in OCD patients and elevated oligoclonal bands in TS patients. For TS and PANDAS groups, there was a dearth of data. Risk of bias assessment indicated a substantial risk of bias in most of the included studies.

CONCLUSIONS

This systematic review of available CSF data shows that too few studies are currently available for conclusions with good evidence. The existing data indicates glutamate alterations in OCD and possible immunological abnormalities in OCD and TS. More CSF studies avoiding sources of bias are needed.

Inflammasome: structure, biological functions, and therapeutic targets

Inflammasomes are a group of protein complex located in cytoplasm and assemble in response to a wide variety of pathogen-associated molecule patterns, damage-associated molecule patterns, and cellular stress. Generally, the activation of inflammasomes will lead to maturation of proinflammatory cytokines and pyroptotic cell death, both associated with inflammatory cascade amplification. A sensor protein, an adaptor, and a procaspase protein interact through their functional domains and compose one subunit of inflammasome complex. Under physiological conditions, inflammasome functions against pathogen infection and endogenous dangers including mtROS, mtDNA, and so on, while dysregulation of its activation can lead to unwanted results. In recent years, advances have been made to clarify the mechanisms of inflammasome activation, the structural details of them and their functions (negative/positive) in multiple disease models in both animal models and human. The wide range of the stimuli makes the function of inflammasome diverse and complex. Here, we review the structure, biological functions, and therapeutic targets of inflammasomes, while highlight NLRP3, NLRC4, and AIM2 inflammasomes, which are the most well studied. In conclusion, this review focuses on the activation process, biological functions, and structure of the most well-studied inflammasomes, summarizing and predicting approaches for disease treatment and prevention with inflammasome as a target. We aim to provide fresh insight into new solutions to the challenges in this field.

Effects of exercise on obsessive-compulsive disorder symptoms: a systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis assessed the efficacy of exercise in reducing OCD symptoms.

METHODS

We searched PubMed, Cochrane Central Register of Controlled Trials, MEDLINE, Scopus and grey literature until March 2022. The study was preregistered at Prospero (CRD42021283931). We included randomised controlled and pre-post trials assessing physical activity as an intervention for OCD. Risk of bias was assessed using the Cochrane ROBINS-I tool and the RoB2 tool.

RESULTS

The analysis included 6 trials (N = 92); 2 were RCTS and 4 were pre-post design studies. A random-effects meta-analysis of pre-post data identified a large reduction of OCD symptoms following exercise (g = 1.33 [95%CI 1.06-1.61]; k = 6). Exercise was also associated with significant pre-post reductions in anxiety (g = 0.71 [95%CI 0.37-1.05; k = 4) and depression (g = 0.57 [95%CI 0.26-0.89]; k = 2). Risk of bias was moderate-high in uncontrolled trials on the ROBINS-I and RCTs showed 'some concerns' on the RoB2.

CONCLUSION

Exercise was associated with a large pre-post reduction of OCD symptoms; however, few trials were of robust quality and all were at risk of bias. Further well-powered and better quality RCTs are required to assess the role of exercise as an intervention for OCD.KEY POINTSStudies exploring exercise as an adjunct therapy for OCD have small participant numbers, therefore a systematic review and meta-analysis is needed to estimate potential efficacy.Pre-post analysis shows that exercise was associated with a large reduction of OCD symptomsThe current systematic review and meta-analysis points to the potential for exercise to be beneficial for the treatment for OCD symptoms. However, more well-powered and better controlled RCTs are required to fully assess the benefit of exercise for the treatment of OCD symptoms.

Autoantibodies in patients with obsessive-compulsive disorder: a systematic review

Obsessive-compulsive disorder (OCD) is a frequent and debilitating mental illness. Although efficacious treatment options are available, treatment resistance rates are high. Emerging evidence suggests that biological components, especially autoimmune processes, may be associated with some cases of OCD and treatment resistance. Therefore, this systematic literature review summarizing all case reports/case series as well as uncontrolled and controlled cross-sectional studies investigating autoantibodies in patients with OCD and obsessive-compulsive symptoms (OCS) was performed. The following search strategy was used to search PubMed: "(OCD OR obsessive-compulsive OR obsessive OR compulsive) AND (antib* OR autoantib* OR auto-antib* OR immunoglob* OR IgG OR IgM OR IgA)". Nine case reports with autoantibody-associated OCD/OCS were identified: five patients with anti-neuronal autoantibodies (against N-methyl-D-aspartate-receptor [NMDA-R], collapsin response mediator protein [CV2], paraneoplastic antigen Ma2 [Ma2], voltage gated potassium channel complex [VGKC], and "anti-brain" structures) and four with autoantibodies associated with systemic autoimmune diseases (two with Sjögren syndrome, one with neuropsychiatric lupus, and one with anti-phospholipid autoantibodies). Six patients (67%) benefited from immunotherapy. In addition, eleven cross-sectional studies (six with healthy controls, three with neurological/psychiatric patient controls, and two uncontrolled) were identified with inconsistent results, but in six studies an association between autoantibodies and OCD was suggested. In summary, the available case reports suggest an association between OCD and autoantibodies in rare cases, which has been supported by initial cross-sectional studies. However, scientific data is still very limited. Thus, further studies on autoantibodies investigated in patients with OCD compared with healthy controls are needed.

Untargeted metabolomics analysis in drug-naïve patients with severe obsessive-compulsive disorder

Introduction

Obsessive-compulsive disorder (OCD), characterized by the presence of obsessions and/or compulsions, is often difficult to diagnose and treat in routine clinical practice. The candidate circulating biomarkers and primary metabolic pathway alteration of plasma in OCD remain poorly understood.

Methods

We recruited 32 drug-naïve patients with severe OCD and 32 compared healthy controls and applied the untargeted metabolomics approach by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) to assess their circulating metabolic profiles. Both univariate and multivariate analyses were then utilized to filtrate differential metabolites between patients and healthy controls, and weighted Correlation Network Analysis (WGCNA) was utilized to screen out hub metabolites.

Results

A total of 929 metabolites were identified, including 34 differential metabolites and 51 hub metabolites, with an overlap of 13 metabolites. Notably, the following enrichment analyses underlined the importance of unsaturated fatty acids and tryptophan metabolism alterations in OCD. Metabolites of these pathways in plasma appeared to be promising biomarkers, such as Docosapentaenoic acid and 5-Hydroxytryptophan, which may be biomarkers for OCD identification and prediction of sertraline treatment outcome, respectively.

Conclusion

Our findings revealed alterations in the circulating metabolome and the potential utility of plasma metabolites as promising biomarkers in OCD.

Pediatric Acute-Onset Neuropsychiatric Syndrome: Current Perspectives

Pediatric acute-onset neuropsychiatric syndrome (PANS) features a heterogeneous constellation of acute obsessive-compulsive disorder (OCD), eating restriction, cognitive, behavioral and/or affective symptoms, often followed by a chronic course with cognitive deterioration. An immune-mediated etiology is advocated in which the CNS is hit by different pathogen-driven (auto)immune responses. This narrative review focused on recent clinical (ie, diagnostic criteria, pre-existing neurodevelopmental disorders, neuroimaging) and pathophysiological (ie, CSF, serum, genetic and autoimmune findings) aspects of PANS. We also summarized recent points to facilitate practitioners with the disease management. Relevant literature was obtained from PubMed database which included only English-written, full-text clinical studies, case reports, and reviews. Among a total of 1005 articles, 205 were pertinent to study inclusion. Expert opinions are converging on PANS as the effect of post-infectious events or stressors leading to "brain inflammation", as it is well-established for anti-neuronal psychosis. Interestingly, differentiating PANS from either autoimmune encephalitides and Sydenham's chorea or from alleged "pure" psychiatric disorders (OCD, tics, Tourette's syndrome), reveals several overlaps and more analogies than differences. Our review highlights the need for a comprehensive algorithm to help both patients during their acute distressing phase and physicians during their treatment decision. A full agreement on the hierarchy of each therapeutical intervention is missing owing to the limited number of randomized controlled trials. The current approach to PANS treatment emphasizes immunomodulation/anti-inflammatory treatments in association with both psychotropic and cognitive-behavioral therapies, while antibiotics are suggested when an active bacterial infection is established. A dimensional view, taking into account the multifactorial origin of psychiatric disorders, should suggest neuro-inflammation as a possible shared substrate of different psychiatric phenotypes. Hence, PANS and PANS-related disorders should be considered as a conceptual framework describing the etiological and phenotypical complexity of many psychiatric disorders.

Peripheral control of psychiatric disorders: Focus on OCD. Are we there yet?

"We are all in this together" - we often hear this phrase when we want to flag up a problem that is not for a single individual but concerns us all. A similar reflection has been recently made in the field of mental disorders where brain-centric scientists have started to zoom out their brain-focused graphical representations of the mechanisms regulating psychiatric diseases to include other organs or mediators that did not belong historically to the world of neuroscience. The brain itself - that has long been seen as a master in command secluded in its fortress (the blood brain barrier), has now become a collection of Airbnb(s) where all sorts of cells come in and out and sometimes even rearrange the furniture! Under this new framework of reference, mental disorders have become multisystem pathologies where different biological systems - not just the CNS -contribute 'all together' to the development and severity of the disease. In this narrative review article, we will focus on one of the most popular biological systems that has been shown to influence the functioning of the CNS: the immune system. We will specifically highlight the two main features of the immune system and the CNS that we think are important in the context of mental disorders: plasticity and memory.

Deep clinical phenotyping of patients with obsessive-compulsive disorder: an approach towards detection of organic causes and first results

In the revised diagnostic classification systems ICD-11 and DSM-5, secondary, organic forms of obsessive-compulsive disorder (OCD) are implemented as specific nosological entities. Therefore, the aim of this study was to clarify whether a comprehensive screening approach, such as the Freiburg-Diagnostic-Protocol for patients with OCD (FDP-OCD), is beneficial for detecting organic OCD forms. The FDP-OCD includes advanced laboratory tests, an expanded magnetic resonance imaging (MRI) protocol, and electroencephalography (EEG) investigations as well as automated MRI and EEG analyses. Cerebrospinal fluid (CSF), [¹⁸F]fluorodeoxyglucose positron emission tomography, and genetic analysis were added for patients with suspected organic OCD. The diagnostic findings of the first 61 consecutive OCD inpatients (32 female and 29 male; mean age: 32.7 ± 12.05 years) analyzed using our protocol were investigated. A probable organic cause was assumed in five patients (8%), which included three patients with autoimmune OCD (one patient with neurolupus and two with specific novel neuronal antibodies in CSF) and two patients with newly diagnosed genetic syndromes (both with matching MRI alterations). In another five patients (8%), possible organic OCD was detected (three autoimmune cases and two genetic cases). Immunological serum abnormalities were identified in the entire patient group, particularly with high rates of decreased "neurovitamin" levels (suboptimal vitamin D in 75% and folic acid in 21%) and increased streptococcal (in 46%) and antinuclear antibodies (ANAs; in 36%). In summary, the FDP-OCD screening led to the detection of probable or possible organic OCD forms in 16% of the patients with mostly autoimmune forms of OCD. The frequent presence of systemic autoantibodies such as ANAs further support the possible influence of autoimmune processes in subgroups of patients with OCD. Further research is needed to identify the prevalence of organic OCD forms and its treatment options.

Neuroinflammation in Obsessive-Compulsive Disorder: Sydenham Chorea, Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections, and Pediatric Acute Onset Neuropsychiatric Syndrome

Sydenham chorea (SC), pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) and pediatric acute-onset neuropsychiatric syndrome (PANS) are postinfectious neuroinflammatory diseases that involve the basal ganglia and have obsessive-compulsive disorder as a major manifestation. As is true for many childhood rheumatological diseases and neuroinflammatory diseases, SC, PANDAS and PANS lack clinically available, rigorous diagnostic biomarkers and randomized clinical trials. Research on the treatment of these disorders depend on three complementary modes of intervention including: treating the symptoms, treating the source of inflammation, and treating disturbances of the immune system. Future studies should aim to integrate neuroimaging, inflammation, immunogenetic, and clinical data (noting the stage in the clinical course) to increase our understanding and treatment of SC, PANDAS, PANS, and all other postinfectious/immune-mediated behavioral disorders.

Early Identification and Intervention in Pediatric Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by persistent thoughts with subsequent repetitive behaviors. Interventions that are effective for adult OCD cannot simply be generalized to pediatric OCD, since OCD in children and adolescents usually has a different clinical presentation, etiology and course from adult OCD. Delayed and inadequate treatment is associated with a worse prognosis, making the need for early identification and intervention in pediatric OCD very urgent. In this paper, we reflected on the current constraints that make early interventions for pediatric OCD unpromoted and reviewed the approaches with potential application for early identification and early intervention in pediatric OCD, categorized by three-level prevention stages corresponding to a clinical staging model. Since the etiology of pediatric OCD is still unclear, primary prevention is most lacking, and early interventions for pediatric OCD are currently focused on the secondary prevention stage, which aims to prevent the conversion of obsessive-compulsive symptoms into full-blown OCD; tertiary prevention mostly focuses on the alleviation of mild to moderate OCD, while interventions for co-morbidities are still in their infancy. We closed by considering the important research questions on this topic.

C-Reactive Protein (CRP): A Potent Inflammation Biomarker in Psychiatric Disorders

An increasing number of studies have investigated the role of inflammation in psychiatric disorders, by demonstrating how an altered/dysfunctional immunological and inflammatory system may underpin a psychiatric condition. Particularly, several studies specifically investigated the role of a neuroinflammatory biomarker, named C-reactive protein (CRP), in psychiatric disorders. Overall, even though scientific literature so far published still does not appear definitive, CRP is more likely reported to be elevated in several psychiatric disorders, including schizophrenia, mood disorders, anxiety disorders and post-traumatic stress disorder. Moreover, a low-grade inflammation (CRP >3 mg/L) has been more likely observed in a subgroup of patients affected with a more severe psychopathological symptomatology, more treatment resistance and worst clinical mental illness course, strengthening the hypothesis of the need for a different clinical and prognostic characterization based on this concomitant neuroinflammatory predisposition. However, even though further research studies are needed to confirm this preliminary evidence, CRP may represent a potential clinical routine biomarker which could be integrated in the clinical routine practice to better characterize clinical picture and course as well as address clinicians towards a personalized treatment.

Obsessive-Compulsive Disorder, PANDAS, and Tourette Syndrome: Immuno-inflammatory Disorders

In the last years, much focus has been given to the possible role of inflammatory and immunologic alterations in the pathophysiology of obsessive-compulsive disorder (OCD) and some related conditions, such as pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS) and Tourette syndrome (TS). Although the matter is intriguing, the available data are still controversial and/or limited. Therefore, the aim of this chapter was at reviewing and commenting on the literature on possible dysfunctions of inflammatory and immune system processes in OCD, PANDAS, and TS.This narrative review was carried out through searching PubMed and Google Scholar for English language papers from January 1985 to December 31, 2021.The data gathered up to now would suggest that the mechanisms involved might be heterogeneous according to the age of the patients and the disorder examined. Indeed, PANDAS seem more related to infections triggering autoimmunity not necessarily following group A beta-hemolytic streptococcal (GABHS) infection, as supposed in the past. Autoimmunity seems also important in TS, if coupled with an individual vulnerability that can be genetic and/or environmental. The data in adult OCD, albeit scattered and sometimes obtained in small samples of patients, would indicate that immune system and inflammatory processes are involved in the pathophysiology of the disorder. However, it is still unclear to conclude whether they are primary or secondary phenomena.In conclusion, taken together, the current findings pave that way towards novel and promising domains to explore the pathophysiology of OCD and related disorders, as well towards the development of innovative therapeutic strategy beyond current pharmacological paradigms.

Back to the Future: The Role of Infections in Psychopathology. Focus on OCD

OBJECTIVE

Recently, there has been a resurgence of interest in the relationship between infections and psychopathology, given the increasing data on the neurotropism and neurological/psychiatric morbidity of the SARS-COV2 virus, responsible for the current worldwide pandemic. Although the majority of observations were those obtained in mood and schizophrenic disorders, a few data are also available on the presence of bacterial or viral infections in patients suffering from obsessive-compulsive disorder (OCD). Therefore, given the limited information, the present paper aimed at reviewing the most updated evidence of infections in neuropsychiatric disorders and their possible mechanisms of actions, with a narrow focus on microbes in OCD.

METHOD

This paper is a narrative review. The databases of PubMed, Scopus, Embase, PsycINFO and Google Scholar were accessed to research and collect English language papers published between 1 January 1980 and 31 December 2021. The data on PANDAS/PANS and those observed during severe brain infections were excluded.

RESULTS

Several pathogens have been associated with an increased risk to develop a broad spectrum of neuropsychiatric conditions, such as schizophrenia, mood disorders, autism, attention-deficit/hyperactivity disorder, anorexia nervosa, and post-traumatic stress disorder. Some evidence supported a possible role of infections also in the pathophysiology of OCD. Infections from Herpes simplex virus 1, Borna disease virus, Group A-Beta Hemolytic Streptococcus, Borrelia spp., and Toxoplasma gondii were actually found in patients with OCD. Although different mechanisms have been hypothesized, all would converge to trigger functional/structural alterations of specific circuits or immune processes, with cascade dysfunctions of several other systems.

CONCLUSIONS

Based on the current evidence, a possible contribution of different types of microbes has been proposed for different neuropsychiatric disorders including OCD. However, the currently available literature is meager and heterogeneous in terms of sample characteristics and methods used. Therefore, further studies are needed to better understand the impact of infectious agents in neuropsychiatric disorders. Our opinion is that deeper insights in this field might contribute to a better definition of biological underpinnings of specific clinical pictures, as well as to promote psychiatric precision medicine, with treatments based on altered pathological pathways of single patients. This might be particularly relevant in OCD, a disorder with a high proportion of patients who are resistant or do not respond to conventional therapeutic strategies.

Children With PANS May Manifest POTS

Objectives

Pediatric acute-onset neuropsychiatric syndrome (PANS) is characterized by an abrupt-onset of severe psychiatric symptoms including OCD, anxiety, cognitive difficulties, and sleep issues which is thought to be a post-infection brain inflammatory disorder. We observed postural orthostatic tachycardia syndrome (POTS) which resolved with immunomodulation in a patient with Pediatric acute-onset neuropsychiatric syndrome (PANS). Here, we aim to present a case of POTS and to examine the prevalence of (POTS) in our PANS cohort, and compare the clinical characteristics of patients with and without POTS.

Study Design

We conducted this cohort study of patients meeting PANS criteria who had at least three clinic visits during the study period. We included data from prospectively collected questionnaires and medical record review. We present a case followed by statistical comparisons within our cohort and a Kaplan-Meier analysis to determine the time-dependent risk of a POTS diagnosis.

Results

Our study included 204 patients: mean age of PANS onset was 8.6 years, male sex (60%), non-Hispanic White (78%). Evidence of POTS was observed in 19/204 patients (9%) with 5/19 having persistent POTS defined as persistent abnormal orthostatic vitals, persistent POTS symptoms, and/or continued need for pharmacotherapy for POTS symptoms for at least 6 months). In this PANS cohort, patients with POTS were more likely to have comorbid joint hypermobility (63 vs 37%, p = 0.04), chronic fatigue (42 vs 18%, p = 0.03), and a family history of chronic fatigue, POTS, palpitations and syncope. An unadjusted logistic regression model showed that a PANS flare (abrupt neuropsychiatric deterioration) was significantly associated with an exacerbation of POTS symptoms (OR 3.3, 95% CI 1.4–7.6, p < 0.01).

Conclusions

Our study describes a high prevalence of POTS in patients with PANS (compared to the general population) and supports an association between POTS presentation and PANS flare within our cohort.

Gene expression study in monocytes: evidence of inflammatory dysregulation in early-onset obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) has a complex etiology that seems to include immune dysfunction and alterations in circulating monocytes. To investigate the immune basis and the functional dysregulation of monocytes in this disease, we analyzed gene expression in the peripheral monocytes of pediatric patients with OCD (N = 102) compared to controls (N = 47). We examined gene expression in primary cultures of peripheral monocytes from participants, under basal conditions and under exposure to lipopolysaccharide (LPS) to stimulate immune response. Whole-genome expression was assessed in 8 patients and 8 controls. Differentially expressed genes were identified followed by protein-protein interaction network construction and functional annotation analysis to identify the genes and biological processes that are altered in the monocytes of OCD patients. We also explored the expression levels of selected genes in monocytes from the other participants using qPCR. Several changes in gene expression were observed in the monocytes of OCD patients, with several immune processes involved under basal conditions (antigen processing and presentation, regulation of immune system and leukocyte cell adhesion) and after LPS stimulation (immune and inflammatory response, cytokine production and leukocyte activation). Despite the qPCR analysis provided no significant differences between patients and controls, high correlations were observed between the expression levels of some of the genes and inflammatory markers (i.e., T helper 17 and regulatory T cell levels, total monocyte and proinflammatory monocyte subset levels, and the cytokine production by resting and stimulated monocytes) of the study participants. Our findings provide more evidence of the involvement of monocyte dysregulation in early-onset OCD, indicating a proinflammatory predisposition and an enhanced immune response to environmental triggers.

Smo-Shh Agonist Purmorphamine Prevents Neurobehavioral and Neurochemical Defects in 8-OH-DPAT-Induced Experimental Model of Obsessive-Compulsive Disorder

Obsessive-compulsive disorder is a mental disorder characterized by repetitive, unwanted thoughts and behavior due to abnormal neuronal corticostriatal-thalamocortical pathway and other neurochemical changes. Purmorphamine is a smoothened-sonic-hedgehog agonist that has a protective effect against many neurological diseases due to its role in maintaining functional connectivity during CNS development and its anti-inflammatory and antioxidant properties. As part of our current research, we investigated the neuroprotective effects of PUR against behavioral and neurochemical changes in 8-hydroxy-2-(di-n-propylamino)-tetralin-induced obsessive-compulsive disorder in rats. Additionally, the effect of PUR was compared with the standard drug for OCD, i.e., fluvoxamine. The intra-dorsal raphe-nucleus injection of 8-OH-DPAT in rats for seven days significantly showed OCD-like repetitive and compulsive behavior along with increased oxidative stress, inflammation, apoptosis, as well as neurotransmitter imbalance. These alterations were dose-dependently attenuated by long-term purmorphamine treatment at 5 mg/kg and 10 mg/kg i.p. In this study, we assessed the level of various neurochemical parameters in different biological samples, including brain homogenate, blood plasma, and CSF, to check the drug’s effect centrally and peripherally. These effects were comparable to the standard oral treatment withfluvoxamine at 10 mg/kg. However, when fluvoxamine was given in combination with purmorphamine, there was a more significant restoration of these alterations than the individualtreatmentswithfluvoxamine and purmorphamine. All the above findings demonstrate that the neuroprotective effect of purmorphamine in OCD can be strong evidence for developing a new therapeutic target for treating and managing OCD.

Obsessive-compulsive disorder and the associated risk of autoimmune skin diseases: a nationwide population-based cohort study

BACKGROUND

The concurrent incidence of autoimmune comorbidities in obsessive-compulsive disorder (OCD) is known. However, the association between OCD and related autoimmune skin diseases (ASDs) has not been well studied.

OBJECTIVE

This study aimed to investigate the association between OCD and the risk of ASDs.

METHODS

To assess the risk of developing ASDs, we recruited 44 324 patients with OCD and 177 296 matched controls from the National Health Insurance Research Database in Taiwan. A Cox regression model was used for the analyses.

RESULTS

After adjusting for confounders, an increased risk of ASDs among the patients with OCD (adjusted hazard ratio [aHR]: 6.36; 95% confidence interval [CI]: 5.43-7.45) was found when compared to the controls. Statistically significant associations were found between OCD and seven individual ASDs, including psoriasis (aHR: 12.52; 95% CI: 8.78-17.85), lichen planus (aHR: 27.22; 95% CI: 13.09-56.60), alopecia areata (aHR: 13.69; 95% CI: 9.38-19.98), autoimmune bullous diseases (aHR: 4.30; 95% CI: 2.03-9.11), hidradenitis suppurativa (aHR: 29.95; 95% CI: 3.35-267.62), vitiligo (aHR: 9.35; 95% CI: 5.35-16.32), and lupus erythematosus (aHR: 2.10; 95% CI: 1.52-2.91).

CONCLUSIONS

Patients with OCD had an increased risk of developing ASDs compared to matched controls. Further studies are required to clarify the underlying mechanisms.

Immunological causes of obsessive-compulsive disorder: is it time for the concept of an "autoimmune OCD" subtype?

Obsessive-compulsive disorder (OCD) is a highly disabling mental illness that can be divided into frequent primary and rarer organic secondary forms. Its association with secondary autoimmune triggers was introduced through the discovery of Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal infection (PANDAS) and Pediatric Acute onset Neuropsychiatric Syndrome (PANS). Autoimmune encephalitis and systemic autoimmune diseases or other autoimmune brain diseases, such as multiple sclerosis, have also been reported to sometimes present with obsessive-compulsive symptoms (OCS). Subgroups of patients with OCD show elevated proinflammatory cytokines and autoantibodies against targets that include the basal ganglia. In this conceptual review paper, the clinical manifestations, pathophysiological considerations, diagnostic investigations, and treatment approaches of immune-related secondary OCD are summarized. The novel concept of "autoimmune OCD" is proposed for a small subgroup of OCD patients, and clinical signs based on the PANDAS/PANS criteria and from recent experience with autoimmune encephalitis and autoimmune psychosis are suggested. Red flag signs for "autoimmune OCD" could include (sub)acute onset, unusual age of onset, atypical presentation of OCS with neuropsychiatric features (e.g., disproportionate cognitive deficits) or accompanying neurological symptoms (e.g., movement disorders), autonomic dysfunction, treatment resistance, associations of symptom onset with infections such as group A streptococcus, comorbid autoimmune diseases or malignancies. Clinical investigations may also reveal alterations such as increased levels of anti-basal ganglia or dopamine receptor antibodies or inflammatory changes in the basal ganglia in neuroimaging. Based on these red flag signs, the criteria for a possible, probable, and definite autoimmune OCD subtype are proposed.

Obsessive-compulsive disorder post-COVID-19: a case presentation

Background

Since the emergence of the COVID-19 pandemic and the significant changes that impacted because of it, people around the world have been left dealing with its consequences—fear of becoming ill and dying, fear of losing loved ones, uncertainty about the future, and imposed social isolation—several elements which could lead to psychological consequences. Moreover, as suggested by recent evidence, the virus acts as a factor in causing psychological symptoms, including depression, anxiety, fatigue, and post-traumatic stress disorder.

Case presentation

Here, we report a case of a patient with new-onset OCD after his recovery from the coronavirus disease, which presented in the form of recurrent and persistent intrusive thoughts and doubts which responded to medication.

Conclusions

This case shows the potential of COVID-19-associated inflammatory triggers to precipitate or induce obsessive–compulsive symptoms. Although this case cannot support causation, it does stress the bidirectional effects that physical and mental illness share.

Elevated serum S100B levels in medication naïve children and adolescents with obsessive-compulsive disorder

PURPOSE

Obsessive-compulsive disorder (OCD) is a condition characterized by obsessions and/or compulsions. S100B protein is shown to be involved in microglial activation besides intracellular signaling, intercellular communication and cell growth. The relation between S100B protein and various psychiatric disorders except OCD has been studied so far. This study aimed to analyze serum S100B levels for the first time in medication naive OCD diagnosed children and adolescents and to compare them with the control group.

MATERIALS AND METHODS

Peripheral blood S100B levels of 27 children and adolescents with OCD were compared to 27 control group subjects to assess any possible association between OCD and S100B levels. All the children and adolescents completed the child version of the Obsessive-Compulsive Inventory (OCI - CV).

RESULTS

Compared to control group, higher serum S100B levels were found in OCD group (z = -2.258, p = 0.024). We also found that obsessing and washing subscales' scores and total score of OCI - CV were statistically significantly correlated with S100B levels (respectively, r = .292, p = 0.032; r = .306, p = 0.025; r = .296, p = 0.030).

CONCLUSIONS

The present study's findings are in accord with previous studies demonstrating the significance of S100B protein in other psychiatric disorders and suggesting a relation in children and adolescents with OCD for the first time. The role of S100B protein in OCD etiology and pathogenesis should be evaluated further.

Genetics of obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a psychiatric disorder with multiple symptom dimensions (e.g. contamination, symmetry). OCD clusters in families and decades of twin studies clearly demonstrate an important role for genetics in the etiology of the disorder.

METHODS

In this review, we summarize the genetic epidemiology and molecular genetic studies of OCD and obsessive-compulsive symptoms.

RESULTS

OCD is a heritable, polygenic disorder with contributions from both common and rare variants, including de novo deleterious variations. Multiple studies have provided reliable support for a large additive genetic contribution to liability to OCD, with discrete OCD symptom dimensions having both shared and unique genetic risks. Genome-wide association studies have not produced significant results yet, likely because of small sample sizes, but larger meta-analyses are forthcoming. Both twin and genome-wide studies show that OCD shares genetic risk with its comorbid conditions (e.g. Tourette syndrome and anorexia nervosa).

CONCLUSIONS

Despite significant efforts to uncover the genetic basis of OCD, the mechanistic understanding of how genetic and environmental risk factors interact and converge at the molecular level to result in OCD's heterogeneous phenotype is still mostly unknown. Future investigations should increase ancestral genetic diversity, explore age and/or sex differences in genetic risk for OCD and expand the study of pharmacogenetics, gene expression, gene × environment interactions and epigenetic mechanisms for OCD.

The Microbiota/Microbiome and the Gut-Brain Axis: How Much Do They Matter in Psychiatry?

The functioning of the central nervous system (CNS) is the result of the constant integration of bidirectional messages between the brain and peripheral organs, together with their connections with the environment. Despite the anatomical separation, gut microbiota, i.e., the microorganisms colonising the gastrointestinal tract, is highly related to the CNS through the so-called "gut-brain axis". The aim of this paper was to review and comment on the current literature on the role of the intestinal microbiota and the gut-brain axis in some common neuropsychiatric conditions. The recent literature indicates that the gut microbiota may affect brain functions through endocrine and metabolic pathways, antibody production and the enteric network while supporting its possible role in the onset and maintenance of several neuropsychiatric disorders, neurodevelopment and neurodegenerative disorders. Alterations in the gut microbiota composition were observed in mood disorders and autism spectrum disorders and, apparently to a lesser extent, even in obsessive-compulsive disorder (OCD) and related conditions, as well as in schizophrenia. Therefore, gut microbiota might represent an interesting field of research for a better understanding of the pathophysiology of common neuropsychiatric disorders and possibly as a target for the development of innovative treatments that some authors have already labelled "psychobiotics".

Association Between Dry Eye Disease and Newly Diagnosed Obsessive-Compulsive Disorder

PURPOSE

The purpose of this study was to evaluate the association between dry eye disease and patients with newly diagnosed obsessive-compulsive disorder (OCD).

METHODS

Thirty treatment-naive patients with OCD and 30 healthy controls were included in this prospective study. The Ocular Surface Disease Index, tear breakup time, Schirmer I test, corneal and conjunctival staining grade (Oxford scale), and neutrophil-to-leucocyte ratio values were obtained for all participants.

RESULTS

The comparison of the patients with OCD and healthy controls showed significantly higher values in Ocular Surface Disease Index (34.8 vs. 20.8, P = 0.001), corneal Oxford scoring (0.9 vs. 0.6, P = 0.02), and conjunctival Oxford scoring (0.8 vs. 0.5, P = 0.04), with consistently lower values in the Schirmer I test (15.7 vs. 18.8, P = 0.043) and tear breakup time (9.1 vs. 12.9, P = 0.001). The mean neutrophil-to-leucocyte ratio values were significantly higher in the OCD group compared with the controls (2.4 ± 0.9 vs. 1.6 ± 0.4, respectively; P = 0.001).

CONCLUSIONS

Our study showed a relation between dry eye disease and patients with newly diagnosed OCD who were not using any psychiatric drug. Our findings suggest that inflammation, which plays an important role in the pathogenesis of both diseases, may be responsible for this relationship.

Are there differences in oxidative stress and inflammatory processes between the autogenous and reactive subtypes of obsessive-compulsive disorder? A controlled cross-sectional study

Objective:

To date, no study has investigated whether autogenous and reactive obsessive-compulsive disorder (OCD) types are different entities in terms of oxidative stress and inflammatory processes. The aim of this study is to compare them in terms of these features.

Methods:

The study was conducted in subjects with reactive OCD (n=19), autogenous OCD (n=14), and a control group (n=17). All participants were non-smokers. Sociodemographic data were collected and the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), Obsessive Beliefs Questionnaire (OBQ), and Overvalued Ideas Scale (OVIS) were administered. High-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), interleukin-10 (IL-10), paraoxonase (PON1), total oxidant status (TOS), and total antioxidant status (TAS) were measured.

Results:

There were no significant differences in TAS, TOS, or oxidative stress index (OSI) between the OCD and control groups. PON1 and hs-CRP levels were higher in the OCD group, whereas IL-6 and IL-10 levels were lower. Comparison across the three groups revealed no differences in TAS, TOS, OSI, or PON1 levels; however, hs-CRP was significantly higher while IL-6 and IL-10 were significantly lower in the reactive group compared to controls.

Conclusion:

Our results show that, although inflammatory processes may play a role in OCD, the autogenous and reactive subtypes do not differ from each other in these respects. The classification of OCD into autogenous and reactive subtypes should be reevaluated.

Elevated levels of neutrophil gelatinase-associated lipocalin among OCD patients: an exploratory study

BACKGROUND

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disease that is characterized by its clinical heterogeneity and complex pathophysiology. This complexity comes from the diversity of pathophysiological factors that have been proposed to be involved in the natural history of the disorder. Many theories on OCD pathology support inflammation as a pathophysiological factor, although studies are not consistent on the presence of a pro-inflammatory state among OCD patients. However, some pre-clinical animal studies suggest lipocalin-2 (LCN2), an analogous form of the acute-phase pro-inflammatory protein neutrophil gelatinase-associated lipocalin (NGAL), may be involved in in the regulation of the stress response, which is thought to be disrupted in OCD.

METHODS

Twenty-one OCD patients and 19 healthy subjects participated in this exploratory study. Levels of NGAL were assessed in the peripherous blood of all participants. Severity of disease was assessed using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS).

RESULTS

OCD patients exhibited significantly higher levels of NGAL when compared to healthy control subjects. No correlation was found between elevated levels of NGAL and severity of symptoms.

CONCLUSIONS

This is the first study to report elevated levels of NGAL among OCD patients, adding evidence for a possible role of immune dysregulation in the pathophysiology of OCD.

Obsessive-Compulsive Disorder With Rheumatological and Inflammatory Diseases: A Systematic Review

Obsessive-compulsive disorder (OCD) is a common mental illness that can significantly impair the patients' quality of life. Recent studies have shown that patients with this condition usually suffer from inflammatory or rheumatological comorbidities. However, the association between OCD's etiology and inflammation is still controversial. This review aims to explore the correlation between OCD and rheumatological as well as inflammatory disorders based on studies conducted in the last decade. A total of eight articles that were deemed eligible were included in the final assessment, involving 31,204 OCD patients from various countries. The most significant inflammatory biomarkers examined were tumor necrosis factor-alpha (TNF-α), interleukins, neutrophil-to-lymphocyte ratio (NLR), and cytokines. We concluded that the pathophysiology and etiology of OCD are strongly correlated with inflammatory biomarkers. This finding warrants future studies on the efficacy of anti-inflammatory agents to treat OCD, particularly in the early stages of the disease.

Cellular and Extracellular White Matter Abnormalities in Obsessive-Compulsive Disorder: A Diffusion Magnetic Resonance Imaging Study

BACKGROUND

While previous studies have implicated white matter (WM) as a core pathology of obsessive-compulsive disorder (OCD), the underlying neurobiological processes remain elusive. This study used free-water (FW) imaging derived from diffusion magnetic resonance imaging to identify cellular and extracellular WM abnormalities in patients with OCD compared with control subjects. Next, we investigated the association between diffusion measures and clinical variables in patients.

METHODS

We collected diffusion-weighted magnetic resonance imaging and clinical data from 83 patients with OCD (56 women/27 men, age 37.7 ± 10.6 years) and 52 control subjects (27 women/25 men, age 32.8 ± 11.5 years). Fractional anisotropy (FA), FA of cellular tissue, and extracellular FW maps were extracted and compared between patients and control subjects using tract-based spatial statistics and voxelwise comparison in FSL Randomise. Next, we correlated these WM measures with clinical variables (age of onset and symptom severity) and compared them between patients with and without comorbidities and patients with and without psychiatric medication.

RESULTS

Patients with OCD demonstrated lower FA (43.4% of the WM skeleton), lower FA of cellular tissue (31% of the WM skeleton), and higher FW (22.5% of the WM skeleton) compared with control subjects. We did not observe significant correlations between diffusion measures and clinical variables. Comorbidities and medication status did not influence diffusion measures.

CONCLUSIONS

Our findings of widespread FA, FA of cellular tissue, and FW abnormalities suggest that OCD is associated with microstructural cellular and extracellular abnormalities beyond the corticostriatothalamocortical circuits. Future multimodal longitudinal studies are needed to understand better the influence of essential clinical variables across the illness trajectory.

Peripartum complications associated with obsessive compulsive disorder exacerbation during pregnancy

Prior research has shown that onset or exacerbation of OCD is associated with menstruation, pregnancy, and the post-partum period. However, the underlying cause is unclear. The goal of this study was to assess whether pregnancy and birth complications were associated with OCD symptoms exacerbation, among women with established OCD. Two-hundred and five (n=205) women with OCD retrospectively reported information on their physical and mental health during their first pregnancy. Over a third of the sample (34%) reported an exacerbation in their OCD symptoms. History of pregnancy and birth complications in the first pregnancy were similar between women who did and did not experience symptom exacerbation, with the exception of gestational diabetes, which was significantly more common among women who experienced exacerbation (7% vs 1%, p=0.03). In a multivariable logistic regression model, gestational diabetes remained significantly associated with exacerbation of OCD symptoms (OR=8.44 [95% CI 1.37-77.27]; p=0.03), even after adjusting for maternal age, OCD severity and treatment, premenstrual OCD symptom increase, stress during pregnancy, and major depression or anxiety disorder diagnosis during pregnancy. We discuss potential explanations for this link. These findings should be treated as hypothesis-generating and need to be replicated in a larger, prospective study.

Searching for host immune-microbiome mechanisms in obsessive-compulsive disorder: A narrative literature review and future directions

Obsessive-compulsive disorder (OCD) is disabling and often treatment-refractory. Host immunity and gut microbiota have bidirectional communication with each other and with the brain. Perturbations to this axis have been implicated in neuropsychiatric disorders, but immune-microbiome signaling in OCD is relatively underexplored. We review support for further pursuing such investigations in OCD, including: 1) gut microbiota has been associated with OCD, but causal pathogenic mechanisms remain unclear; 2) early environmental risk factors for OCD overlap with critical periods of immune-microbiome development; 3) OCD is associated with increased risk of immune-mediated disorders and changes in immune parameters, which are separately associated with the microbiome; and 4) gut microbiome manipulations in animal models are associated with changes in immunity and some obsessive-compulsive symptoms. Theoretical pathogenic mechanisms could include microbiota programming of cytokine production, promotion of expansion and trafficking of peripheral immune cells to the CNS, and regulation of microglial function. Immune-microbiome signaling in OCD requires further exploration, and may offer novel insights into pathogenic mechanisms and potential treatment targets for this disabling disorder.

Caspase-11 Noncanonical Inflammasome: A Novel Key Player in Murine Models of Neuroinflammation and Multiple Sclerosis

Inflammasomes are intracellular protein complexes consisting of the pattern recognition receptors and inflammatory molecules in the inflamed cells. In response to various ligands, inflammasomes play a pivotal role to execute the inflammatory responses by inducing the pyroptosis and the secretion of pro-inflammatory cytokines, interleukin (IL)-1β, and IL-18. Unlike canonical inflammasomes, including NOD-like receptor family inflammasomes, such as NLRP1, NLRP3, NLRC4, and absence in melanoma 2 inflammasomes, noncanonical inflammasomes, such as mouse caspase-11 and human caspase-4/5 were recently discovered, and their roles in the inflammatory responses have been poorly understood. However, emerging studies have been successfully demonstrating the regulatory roles of these noncanonical inflammasomes on inflammatory responses and the pathogenesis of inflammatory/autoimmune diseases. This review summarizes and discusses the recent studies investigating the regulatory roles of the caspase-11 noncanonical inflammasome in neuroinflammation and the pathogenesis of multiple sclerosis (MS), which provides the insight for the validation of caspase-11 noncanonical inflammasome to develop novel and promising therapeutics for MS.

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.

Associations Between Subclinical Inflammatory Markers and OCD: A Retrospective Study

Obsessive-compulsive disorder (OCD) is characterized by unwanted, intrusive and disturbing thoughts or images that cause anxiety and repetitive behaviours or mental acts to relieve these thoughts or images. Considering controversial aetiology of OCD and growing evidence for the role of inflammation in OCD, the aim of this study was to examine the association between OCD and subclinical inflammatory markers, namely neutrophil-to-lymphocyte ratio(NLR) and platelet-to-lymphocyte ratio(PLR) in adult patients and to investigate the association between antidepressant medications and NLR, PLR. Electronic medical records(EMR) of 24,635 patients aged 18-64 were reviewed and after exclusion of comorbid psychiatric and medical diagnosis 135 EMR of OCD patients were included into final analyses and compared with the healthy control group (n=133). Blood cell counts were noted to calculate NLR and PLR. Medications of patients were gathered from all patients to calculate fluoxetine-equivalent-dose(FED) to examine the effects of antidepressants on NLR and PLR. NLR and PLR were significantly higher in OCD. Contrary to the correlation of FED with NLR, PLR was found to not correlate with FED. Hence, PLR would be considered as a robust biomarker to medication effect contrary to NLR. OCD was significantly predicted by both NLR and PLR in logistic regression analyzes.

Association of Pediatric Acute-Onset Neuropsychiatric Syndrome With Microstructural Differences in Brain Regions Detected via Diffusion-Weighted Magnetic Resonance Imaging

IMPORTANCE

Epidemiological studies indicate a link between obsessive-compulsive disorder and infections, particularly streptococcal pharyngitis. Pediatric acute-onset neuropsychiatric syndrome (PANS) manifests suddenly with obsessions, compulsions, and other behavioral disturbances, often after an infectious trigger. The current working model suggests a unifying inflammatory process involving the central nervous system, particularly the basal ganglia.

OBJECTIVE

To investigate whether diffusion-weighted magnetic resonance imaging (DWI) detects microstructural abnormalities across the brain regions of children with PANS.

DESIGN, SETTING, AND PARTICIPANTS

Case-control study performed at a single-center, multidisciplinary clinic in the United States focusing on the evaluation and treatment of children with PANS. Sixty consecutive patients who underwent 3 Tesla (T) magnetic resonance imaging (MRI) before immunomodulation from September 3, 2012, to March 30, 2018, were retrospectively reviewed for study inclusion. Six patients were excluded by blinded investigators because of imaging or motion artifacts, 3 patients for major pathologies, and 17 patients for suboptimal atlas image registration. In total, 34 patients with PANS before initiation of treatment were compared with 64 pediatric control participants.

MAIN OUTCOMES AND MEASURES

Using atlas-based MRI analysis, regional brain volume, diffusion, and cerebral blood flow were measured in the cerebral white matter, cerebral cortex, thalamus, caudate, putamen, pallidum, hippocampus, amygdala, nucleus accumbens, and brainstem. An age and sex-controlled multivariable analysis of covariance was used to compare patients with control participants.

RESULTS

This study compared 34 patients with PANS (median age, 154 months; age range, 55-251 months; 17 girls and 17 boys) and 64 pediatric control participants (median age, 139 months; age range, 48-213 months); 41 girls and 23 boys). Multivariable analysis demonstrated a statistically significant difference in MRI parameters between patients with PANS and control participants (F21,74 = 6.91; P < .001; partial η2 = 0.662). All assessed brain regions had statistically significantly increased median diffusivity compared with 64 control participants. Specifically, the deep gray matter (eg, the thalamus, basal ganglia, and amygdala) demonstrated the most profound increases in diffusivity consistent with the cardinal clinical symptoms of obsessions, compulsions, emotional dysregulation, and sleep disturbances. No statistically significant differences were found regarding volume and cerebral blood flow.

CONCLUSIONS AND RELEVANCE

This study identifies cerebral microstructural differences in children with PANS in multiple brain structures, including the deep gray matter structures (eg, the thalamus, basal ganglia, and amygdala). Further study of MRI is warranted in prospective, clinical trials as a potential quantitative method for assessing patients under evaluation for PANS.

P2X7 receptor knockout mice display less aggressive biting behaviour correlating with increased brain activation in the piriform cortex

P2X₇ receptors are implicated in the pathophysiology of psychiatric conditions such as depression and bipolar disorder. P2X₇ receptors regulate the release of pro-inflammatory cytokines from microglia, and gain-of-function P2X₇ mutations may contribute to the neuroinflammation found in affective disorders. However, the role of this receptor in mediating other mental health conditions and aberrant behaviours requires further examination. The current study we investigated the effects of germline genetic deletion of P2xr7 on social and marble burying behaviours in mice throughout the critical adolescent developmental period. Marble burying behaviour is thought to provide a mouse model of obsessive-compulsive disorder (OCD). We also characterised the effects of P2rx7 deletion on aggressive attack behaviour in adult mice and subsequently quantifieded microglial cell densities and c-Fos expression, a marker of neuronal activation. P2rx7 knockout mice displayed reduced OCD-related marble burying behaviour which was most pronounced in late adolescence/early adulthood. P2rx7 knockout mice also exhibited reduced aggressive attack behaviours in adulthood in the resident-intruder test. Reduced aggression in P2xr7 knockout mice did not coincide with changes to microglial cell densities, however c-Fos expression was elevated in the piriform cortex of P2rx7 knockout mice compared to wildtype mice. This study suggests that the P2X₇ receptor might serve as a novel target for serenic or anti-OCD therapeutics.

Investigating the Role of Glutamate in Obsessive-Compulsive Disorder: Current Perspectives

Glutamate is a ubiquitous excitatory neurotransmitter, which is involved in normal physiology, a variety of central nervous system (CNS) functions, including excitotoxicity and neuronal migration. It is implicated in the pathogenesis of various neuropsychiatric disorders including epilepsy, Parkinson's disease, Alzheimer's dementia, schizophrenia and obsessive compulsive disorder (OCD). Over the years, a growing body of evidence has helped researchers understand the mechanisms underlying glutamatergic involvement in the pathogenesis of these disorders. In this review, we attempt to elucidate the role of glutamate in OCD, which is a chronic psychiatric condition with significant morbidity. This article provides current perspectives on the role played by glutamate in the pathogenesis, clinical symptoms and treatment response in OCD, a critical analysis of existing and emerging evidence, both clinical and preclinical, followed by a summary and future directions.