Recent advances in the genetics of obsessive-compulsive disorder

Stressful Life Events and the Clinical Expression of Obsessive-Compulsive Disorder (OCD): An Exploratory Study

BACKGROUND

In obsessive-compulsive disorder (OCD), symptom content and severity appear to fluctuate over the course of the life cycle in accordance with stressful life events. The objective of this paper was to compare OCD patients with and without reported stressful life events (SLEs) in terms of the sociodemographics of patients and the clinical characteristics of OCD.

METHODS

This was a cross-sectional study involving 1001 patients with OCD. Data concerning SLEs were collected via the Yale OCD Natural History Questionnaire, while for OCD symptoms, the Dimensional Yale-Brown Obsessive-Compulsive Scale was used.

RESULTS

Of the 1001 OCD patients, 605 (60.5%) reported experiencing at least one SLE in their lifetime. Self-declared nonwhite skin color (odds ratio (OR) = 1.51), the presence of a sensory phenomenon (OR = 1.47), and comorbidity with post-traumatic stress disorder (PTSD) (OR = 2.38) were some of the logistic regression variables related to the reported SLEs with relevant statistical significance and risk (i.e., OR) values.

CONCLUSIONS

Our results indicate that SLEs may make Brazilian OCD patients vulnerable to the onset or exacerbation of obsessive-compulsive symptoms. The positive association of the occurrence of SLEs and sensory phenomena in this population could corroborate that environmental influences impact the neurobiology associated with OCD, and likely with other psychiatric disorders as well.

Interaction between PGRN gene and the early trauma on clinical characteristics in patients with obsessive-compulsive disorder

BACKGROUND

Emerging evidence suggests that obsessive-compulsive disorder (OCD) is caused by a combination of genetic predisposition and environmental factors. In this regard, abnormity of progranulin (PGRN, a key regulator of brain inflammation) and a history of childhood trauma have both been linked to an increased risk of developing OCD. This study is aimed to investigate the association between PGRN and childhood trauma in the development of OCD.

METHODS

We genotyped four single nucleotide polymorphisms (SNPs) covering PGRN in 484 OCD patients and 368 healthy controls. Among the OCD patients, 335 of them accepted clinical assessments in details. Generalized multifactor dimensionality reduction (GDMR) analysis and a general linear model were used to identify gene-environment interactions. The Braineac expression Quantitative Trait Loci (eQTL) dataset was used to analyze the differences in PGRN expression in various brain regions among different genotypes.

RESULTS

Our linkage disequilibrium analysis revealed that rs3859268-rs2879096-rs3785817 combined OCD and control groups constructed one haplotype block. The haplotype analysis suggested that TCA haplotype frequency was associated with the risk of developing OCD (Padj=0.03). The Braineac eQTL database revealed that rs2879096 and rs3785817 might be associated with PGRN expression in the hippocampus (Padj=0.00085, Padj=0.007). Emotional abuse was positively correlated with the obsession subscale and Y-BOCS total scores. Except for common trauma, physical abuse, emotional abuse and sexual trauma were all positively correlated with the BAI and BDI-II scores of OCD patients (all P<0.05). The interaction between emotional abuse and PGRN haplotype was associated with the development of depression symptoms in OCD patients corrected by age (Padj=0.043).

CONCLUSIONS

The PGRN gene and childhood trauma may be closely related to the incidence of OCD, and OCD patients who have experienced more childhood trauma may exhibit a more severe clinical symptom. The interaction between PGRN and the early trauma may play a critical role in the development of depression symptom in OCD patients.

Genetics of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) has been seen to run in families and genetics help to understand its heritability. In this review, we summarize older studies which focused on establishing the familial nature of OCD, including its various dimensions of symptoms, and we focus on recent findings from studies using both the candidate gene approach and genome-wide association study (GWAS) approach. The family studies and twin studies establish the heritability of OCD. Candidate gene approaches have implicated genes in the serotonergic, glutamatergic, and dopaminergic pathways. GWAS has not produced significant results possibly due to the small sample size. Newer techniques such as gene expression studies in brain tissue, stem cell technology, and epigenetic studies may shed more light on the complex genetic basis of OCD.

DNA damage and antioxidants in treatment naïve children with obsessive-compulsive disorder

The current study aimed to investigate whether serum antioxidant levels and DNA damage differ between the children and adolescents with Obsessive Compulsive Disorder (OCD) and healthy controls. The study included 31 children (Male/Female, 22/9; age range 7-17 years), with treatment naïve OCD diagnosed according to Diagnostic and Statistical Manual of Mental Disorders-V (DSM-V) and 28 age- and gender-matched healthy control subjects. Children's Yale Brown Obsession Compulsion Scale (CY-BOC) was applied to the children. Glutathione peroxidase (GPx), superoxide dismutase (SOD), coenzyme Q (CoQ), and 8-Hydroxy-2-Deoxyguanosine (8-OHdG) were all measured by the enzyme-linked immunosorbent assay method. GPx, CoQ and 8-OHdG levels were found to be significantly higher in the OCD group, compared to the control group (p=0.010, p=0.034, p=0.010, respectively); however, no significant difference was found in the SOD levels between two groups (p=0.10). There were no correlations between the CY-BOC scores, depression scores, duration of the disease and biochemical parameters (p>0.05, for all). Children with OCD were found to have higher antioxidant levels and oxidative DNA damage. The findings of this study support the role of oxidative stress in the pathogenesis of OCD. In this regard, any possible effect of adding antioxidants to conventional treatment can be investigated.

Early-life adversity and orbitofrontal and cerebellar volumes in adults with obsessive-compulsive disorder: voxel-based morphometry study

BACKGROUND

Early-life adversity is a risk for obsessive-compulsive disorder (OCD), but the impact at the neural level is less clear.

AIMS

To investigate the association between brain volumes and early-life adversity in individuals with a diagnosis of OCD only.

METHOD

The Childhood Trauma Questionnaire (CTQ-28) was used to assess early-life adversity in 21 participants with OCD and 25 matched healthy controls. The relationship between global and regional brain volume and early-life adversity was measured using voxel-based morphometry (VBM). All data were corrected for multiple comparisons using family-wise error (FWE) at P<0.05.

RESULTS

In the OCD group, correlations with total CTQ scores were positively associated with a larger right orbitofrontal cortex volume. Physical neglect was higher in the OCD group than in controls and was positively associated with larger right cerebellum volume in the OCD group only.

CONCLUSIONS

Larger brain volumes may reflect underlying developmental neuropathology in adults with OCD who also have experience of childhood trauma.

From Thought to Action: How the Interplay Between Neuroscience and Phenomenology Changed Our Understanding of Obsessive-Compulsive Disorder

The understanding of obsessive-compulsive disorder (OCD) has evolved with the knowledge of behavior, the brain, and their relationship. Modern views of OCD as a neuropsychiatric disorder originated from early lesion studies, with more recent models incorporating detailed neuropsychological findings, such as perseveration in set-shifting tasks, and findings of altered brain structure and function, namely of orbitofrontal corticostriatal circuits and their limbic connections. Interestingly, as neurobiological models of OCD evolved from cortical and cognitive to sub-cortical and behavioral, the focus of OCD phenomenology also moved from thought control and contents to new concepts rooted in animal models of action control. Most recently, the proposed analogy between habitual action control and compulsive behavior has led to the hypothesis that individuals suffering from OCD may be predisposed to rely excessively on habitual rather than on goal-directed behavioral strategies. Alternatively, compulsions have been proposed to result either from hyper-valuation of certain actions and/or their outcomes, or from excessive uncertainty in the monitoring of action performance, both leading to perseveration in prepotent actions such as washing or checking. In short, the last decades have witnessed a formidable renovation in the pathophysiology, phenomenology, and even semantics, of OCD. Nevertheless, such progress is challenged by several caveats, not least psychopathological oversimplification and overgeneralization of animal to human extrapolations. Here we present an historical overview of the understanding of OCD, highlighting converging studies and trends in neuroscience, psychiatry and neuropsychology, and how they influenced current perspectives on the nosology and phenomenology of this disorder.

Gender differences in obsessive-compulsive disorder: findings from a large Indian sample

AIM

Gender has been considered as one of the possible factors mediating phenotypic expression of obsessive-compulsive disorder (OCD). We examined gender differences in a large sample of subjects with OCD from India with respect to socio-demographic parameters, symptom characteristics, and comorbidity patterns.

METHODS

Consecutive patients (n=545) who consulted a specialty OCD clinic over 5 years at a large psychiatric hospital in India were evaluated.

RESULTS

Men (n=332) compared to women (n=213) with OCD had an earlier onset (p<0.001), higher frequency of sexual (p<0.001) and religious obsessions (p=0.001) pathological doubts (p<0.001) and checking (p<0.001) and repeating compulsions (p<0.001), and a greater tendency to have comorbid social phobia (p=0.006). Women compared to men were more likely to be married, had a higher frequency of fear of contamination (p=0.017), comorbid depression (p=0.014) and greater suicidal risk (p=0.003).

CONCLUSIONS

Our study provides further evidence for gender related differences in clinical features of obsessive-compulsive disorder. Our findings are only partly comparable with results from studies across the world possibly due to various biological and cultural factors mediating the phenotypic expression of OCD across the genders. There is a need to examine the biological basis for these gender differences.

BDNF Val66Met modifies the risk of childhood trauma on obsessive-compulsive disorder

Childhood trauma has been linked to the development of later psychopathology, including obsessive-compulsive disorder (OCD). Although evidence exists to suggest that genetic and environmental factors are involved in the aetiology of OCD, little attention has been paid to the interactions that exist between genes and environment. The aim of this study was to investigate gene-by-environment interactions between childhood trauma and the BDNF Val66Met variant in patients with OCD. Childhood trauma was assessed in 134 OCD patients and 188 controls using the Childhood Trauma Questionnaire (CTQ). Linear regression models were used for statistical analyses. Gene-environment interactions were estimated by including a combined genotype and CTQ score in the models as interaction terms. All analyses were adjusted for age, gender, CTQ minimisation-denial score and home language by including them in the logistic regression models as covariates. Childhood trauma, specifically emotional abuse and neglect, increased the odds of having OCD significantly (p < 0.001). Although no significant association was observed between BDNF Val66Met and the development of OCD, interaction analysis indicated that the BDNF Met-allele interacted with childhood emotional abuse to increase the risk of OCD significantly in a dose-dependent manner (p = 0.024). To our knowledge, this is one of the first studies to investigate gene-environment interactions in OCD, and the findings indicate the importance of collating genetic and environmental variables in future studies.

DRD4 gene and obsessive compulsive disorder: do symptom dimensions have specific genetic correlates?

INTRODUCTION

The dopamine D4 receptor (DRD4) is a promising candidate gene in obsessive compulsive disorder (OCD). A 48-bp variable number of tandem repeats (VNTR) sequence in exon 3 has been studied previously, and alleles containing 2-11 repeats (2R-11R) have been identified. We investigated the association of DRD4 VNTR polymorphism with OCD and its relationship with various clinical parameters (age of onset, gender, family history, co-morbidity, factor-analyzed symptom dimensions and insight).

METHODOLOGY

One hundred and seventy three South Indian OCD patients (DSM-IV) recruited from a specialty OCD clinic were evaluated using the Yale-Brown obsessive compulsive scale (YBOCS), YBOCS item-11 for insight, Mini International Neuropsychiatric Interview (MINI) plus, tic disorder subsection of the MINI-KID and Clinical Global Impression scale. 201 healthy controls were evaluated using MINI plus. All subjects were genotyped for the DRD4 VNTR polymorphism.

RESULTS

Genotype frequencies did not deviate significantly from the Hardy-Weinberg equilibrium. Case-control association analysis revealed that the 7R allele frequency was significantly greater in OCD patients than controls. This difference was restricted to the women subsample when performing the gender sub-analysis. Among other clinical variables examined, factor 3 (symmetry) was associated with presence of 2R allele. Linear regression analysis confirmed the association of symmetry dimension with the 2R allele (Beta=0.23, t=2.96, p=0.004, CI=0.19-0.95).

CONCLUSIONS

Our data provides further evidence that DRD4 VNTR polymorphism is associated with OCD. Furthermore, the presence of the 2R allele was significantly associated with the symmetry dimension. This dimension may represent a more homogeneous subtype of OCD with a genetic etiology.

Impact of depressive and anxiety disorder comorbidity on the clinical expression of obsessive-compulsive disorder

BACKGROUND

The identification of distinct subtypes based on comorbidity offers potential utility in understanding variations in the clinical expression of obsessive-compulsive disorder (OCD). Hence, we examined the hypothesis whether patients with OCD with major depressive disorder (MDD) or anxiety disorder comorbidity would differ from those without in terms of phenomenology.

METHODS

A total of 545 consecutive patients who consulted a specialty OCD clinic during the period 2004 to 2009 at a psychiatric hospital in India formed the sample. They were evaluated with the Yale-Brown Obsessive-Compulsive Scale (YBOCS), the Mini International Neuropsychiatric Interview, and the Clinical Global Impression scale.

RESULTS

Among 545 patients, 165 (30%) had current MDD, and 114 (21%) had current anxiety disorder comorbidity. Patients with OCD with MDD were mostly women who had a greater severity of OCD symptoms, more of obsessions (especially religious), greater occurrence of miscellaneous compulsions (need to confess or need to touch), higher suicidal risk, and past suicidal attempts. Patients with OCD with anxiety disorder had an earlier onset of illness that was associated with prior life events, less of compulsions, more of aggressive and hoarding obsessions, pathologic doubts, checking, and cognitive compulsions.

CONCLUSIONS

Obsessive-compulsive disorder, when comorbid with MDD, is more severe and is associated with higher suicidal risk. On the other hand, anxiety disorder comorbidity seems to influence not so much the morbidity but the phenotypic expression of OCD.

Interaction of SLC1A1 gene variants and life stress on pharmacological resistance in obsessive-compulsive disorder

Genetic and environmental factors seem to interact and influence both the onset and the course of obsessive-compulsive disorder (OCD), but the role of glutamate transporter variants (SLC1A1) in pharmacological resistance is not known. We aimed to assess whether genetic variants in SLC1A1 and life stress at onset of the disorder interact and modulate pharmacological resistance in OCD. A single-marker association study of several single-nucleotide polymorphisms in the SLC1A1 genomic region was performed in a sample of 238 OCD patients. For the most strongly associated SNP (rs3087879), one copy of the risk allele increased the probability of higher treatment resistance (odds ratio=2.42; 95% confidence interval=1.39-4.21; P=0.0018), but only in OCD patients without life stress at onset of the disorder. These results suggest a gene-by-environment interaction effect on treatment resistance in OCD and strengthen the existing evidence of the role of the glutamatergic system in the phenomenology of OCD.

Acquisition and baseline performance of working memory tasks by adolescent rhesus monkeys

Adolescence is a transitional stage of development characterized by protracted refinements in the neural circuits required for adult level proficiency of working memory. Because impaired working memory is a hallmark feature of several psychiatric disorders that have their onset during adolescence, model systems that can be used to assess the maturation of working memory function, and of disease-related risk factors that disrupt its development, are of particular importance. However, few studies have investigated the maturation of working memory in nonhuman primates. Thus in the present study, we adapted two working memory tests that are among the most widely used in human and adult nonhuman primates, for adolescent rhesus monkeys. Using a touch-screen apparatus, monkeys were trained on a spatial delayed-response task to assess spatial working memory and a delayed match-to-sample task to assess object working memory. The results indicate that adolescent rhesus monkeys readily and efficiently acquire the ability to perform touch-screen based, complex tests of working memory. These data establish that distinct components of adult prefrontal cortex-dependent cognitive functions can be effectively modeled and evaluated in adolescent monkeys. As such, this approach should be useful for assessing the influence of environmental risk factors on the protracted maturation of working memory in adolescent macaques.

Executive dysfunctions in obsessive-compulsive patients and unaffected relatives: searching for a new intermediate phenotype

BACKGROUND

Evidence in literature suggests that neurocognitive deficits may represent suitable intermediate-phenotype candidates for the dissection of obsessive-compulsive disorder (OCD) genetic heterogeneity. The aim of this study was to search for possible OCD neurocognitive endophenotypes by assessing decision-making, planning, and mental flexibility profiles in OCD probands, healthy control subjects (HC), and their respective relatives.

METHODS

The sample consisted of 35 pairs of OCD probands without other Axis I comorbidities and unaffected first-degree relatives and 31 pairs of HC subjects without a known family history of OCD and their relatives. Neuropsychological assessment was performed using the Iowa Gambling Task (IGT), the Tower of Hanoi (ToH), and the Wisconsin Card Sorting Test (WCST).

RESULTS

Obsessive-compulsive disorder patients showed impairments in decision making, planning, and mental flexibility, given that OCD probands performed significantly poorer than HC probands at the IGT, the ToH, and the WCST. Obsessive-compulsive disorder relatives performed poorer at these tests than HC probands and relatives. Symptom severity was found to have no influence on neurocognitive performance. Analysis of proband/relative concordance in task performance was performed for each task. A significant overall difference was found when comparing the percentages of the different concordance profiles of our OCD and HC samples with regard to IGT and ToH performance. No significant difference was found in the WCST.

CONCLUSIONS

Executive dysfunctions may qualify as a suitable endophenotype candidate for OCD. Concordance rates in neuropsychological task performance suggest that decision-making and planning deficits aggregate in these families and therefore might be a heritable component of OCD.

Obsessive-compulsive disorder and its related disorders: a reappraisal of obsessive-compulsive spectrum concepts

Obsessive-compulsive disorder (OCD) is a clinical syndrome whose hallmarks are excessive, anxiety-evoking thoughts and compulsive behaviors that are generally recognized as unreasonable, but which cause significant distress and impairment. When these are the exclusive symptoms, they constitute uncomplicated OCD. OCD may also occur in the context of other neuropsychiatric disorders, most commonly other anxiety and mood disorders. The question remains as to whether these combinations of disorders should be regarded as independent, cooccurring disorders or as different manifestations of an incompletely understood constellation of OCD spectrum disorders with a common etiology. Additional considerations are given here to two potential etiology-based subgroups: (i) an environmentally based group in which OCD occurs following apparent causal events such as streptococcal infections, brain injury, or atypical neuroleptic treatment; and (ii) a genomically based group in which OCD is related to chromosomal anomalies or specific genes. Considering the status of current research, the concept of OCD and OCD-related spectrum conditions seems fluid in 2010, and in need of ongoing reappraisal.