Discover the most talked about and latest scientific content & concepts.

Concept: Obsessive–compulsive disorder


Obsessive-compulsive disorder (OCD) has become a paradigmatic case of goal-directed dysfunction in psychiatry. In this article, we review the neurobiological evidence, historical and recent, that originally led to this supposition and continues to support a habit hypothesis of OCD. We will then discuss a number of recent studies that have directly tested this hypothesis, using behavioural experiments in patient populations. Based on this research evidence, which suggests that rather than goal-directed avoidance behaviours, compulsions in OCD may derive from manifestations of excessive habit formation, we present the details of a novel account of the functional relationship between these habits and the full symptom profile of the disorder. Borrowing from a cognitive dissonance framework, we propose that the irrational threat beliefs (obsessions) characteristic of OCD may be a consequence, rather than an instigator, of compulsive behaviour in these patients. This lays the foundation for a potential shift in both clinical and neuropsychological conceptualization of OCD and related disorders. This model may also prove relevant to other putative disorders of compulsivity, such as substance dependence, where the experience of ‘wanting’ drugs may be better understood as post hoc rationalizations of otherwise goal-insensitive, stimulus-driven behaviour.

Concepts: Psychology, Patient, Cognition, Behavior, Human behavior, Obsessive–compulsive disorder, Compulsive behavior


Obsessive-compulsive disorder is a severe psychiatric disorder linked to abnormalities in glutamate signaling and the cortico-striatal circuit. We sequenced coding and regulatory elements for 608 genes potentially involved in obsessive-compulsive disorder in human, dog, and mouse. Using a new method that prioritizes likely functional variants, we compared 592 cases to 560 controls and found four strongly associated genes, validated in a larger cohort. NRXN1 and HTR2A are enriched for coding variants altering postsynaptic protein-binding domains. CTTNBP2 (synapse maintenance) and REEP3 (vesicle trafficking) are enriched for regulatory variants, of which at least six (35%) alter transcription factor-DNA binding in neuroblastoma cells. NRXN1 achieves genome-wide significance (p = 6.37 × 10(-11)) when we include 33,370 population-matched controls. Our findings suggest synaptic adhesion as a key component in compulsive behaviors, and show that targeted sequencing plus functional annotation can identify potentially causative variants, even when genomic data are limited.Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder with symptoms including intrusive thoughts and time-consuming repetitive behaviors. Here Noh and colleagues identify genes enriched for functional variants associated with increased risk of OCD.

Concepts: DNA, Gene, Archaea, Molecular biology, Psychiatry, Body dysmorphic disorder, Obsessive–compulsive disorder, Compulsive behavior


Obsessive Compulsive Disorder (OCD) is a chronic and disabling disorder with poor response to pharmacological treatments. Converging evidences suggest that OCD patients suffer from dysfunction of the cortico-striato-thalamo-cortical (CSTC) circuit, including in the medial prefrontal cortex (mPFC) and the anterior cingulate cortex (ACC).

Concepts: Medicine, Brain, Cerebrum, Limbic system, Brodmann area 24, Anterior cingulate cortex, Cingulate cortex, Obsessive–compulsive disorder


Cognitive behavioral therapy (CBT) and selective serotonin reuptake inhibitors (SSRIs) are both effective treatments for some patients with obsessive-compulsive disorder (OCD), yet little is known about the neurochemical changes related to these treatment modalities. Here, we used positron emission tomography and the α-[11C]methyl-L-tryptophan tracer to examine the changes in brain regional serotonin synthesis capacity in OCD patients following treatment with CBT or SSRI treatment. Sixteen medication-free OCD patients were randomly assigned to 12 weeks of either CBT or sertraline treatment. Pre-to-post treatment changes in the α-[11C]methyl-L-tryptophan brain trapping constant, K* (ml/g/min), were assessed as a function of symptom response, and correlations with symptom improvement were examined. Responders/partial responders to treatment did not show significant changes in relative regional tracer uptake; rather, in responders/partial responders, 12 weeks of treatment led to serotonin synthesis capacity increases that were brain-wide. Irrespective of treatment modality, baseline serotonin synthesis capacity in the raphe nuclei correlated positively with clinical improvement. These observations suggest that, for some patients, successful remediation of OCD symptoms might be associated with greater serotonergic tone.

Concepts: Positron emission tomography, Serotonin, Fluvoxamine, Antidepressant, Selective serotonin reuptake inhibitor, Major depressive disorder, Sertraline, Obsessive–compulsive disorder


We assessed the role of prenatal maternal smoking in risk for Tourette syndrome and chronic tic disorder (TS/CT) and pediatric-onset obsessive-compulsive disorder (OCD).

Concepts: Tourette syndrome, Treatment of Tourette syndrome, Tic, Tic disorder, Obsessive–compulsive disorder, Tourettism


Orthorexia nervosa describes a pathological obsession with proper nutrition that is characterized by a restrictive diet, ritualized patterns of eating, and rigid avoidance of foods believed to be unhealthy or impure. Although prompted by a desire to achieve optimum health, orthorexia may lead to nutritional deficiencies, medical complications, and poor quality of life. Despite its being a distinct behavioral pattern that is frequently observed by clinicians, orthorexia has received very little empirical attention and is not yet formally recognized as a psychiatric disorder. In this review, we synthesize existing research to identify what is known about the symptoms, prevalence, neuropsychological profile, and treatment of orthorexia. An examination of diagnostic boundaries reveals important points of symptom overlap between orthorexia and anorexia nervosa, obsessive-compulsive disorder (OCD), obsessive-compulsive personality disorder (OCPD), somatic symptom disorder, illness anxiety disorder, and psychotic spectrum disorders. Neuropsychological data suggest that orthorexic symptoms are independently associated with key facets of executive dysfunction for which some of these conditions already overlap. Discussion of cognitive weaknesses in set-shifting, external attention, and working memory highlights the value of continued research to identify intermediate, transdiagnostic endophenotypes for insight into the neuropathogenesis of orthorexia. An evaluation of current orthorexia measures indicates a need for further psychometric development to ensure that subsequent research has access to reliable and valid assessment tools. Optimized assessment will not only permit a clearer understanding of prevalence rates, psychosocial risk factors, and comorbid psychopathology but will also be needed to index intervention effectiveness. Though the field lacks data on therapeutic outcomes, current best practices suggest that orthorexia can successfully be treated with a combination of cognitive-behavioral therapy, psychoeducation, and medication.

Concepts: Psychology, Anorexia nervosa, Eating disorders, Psychiatry, Body dysmorphic disorder, Obsessive–compulsive disorder, Obsessive–compulsive personality disorder, Orthorexia nervosa


A recent hypothesis has suggested that core deficits in goal-directed behavior in obsessive-compulsive disorder (OCD) are caused by impaired frontostriatal function. We tested this hypothesis in OCD patients and control subjects by relating measures of goal-directed planning and cognitive flexibility to underlying resting-state functional connectivity.

Concepts: Obsessive–compulsive disorder


Confidence and actions are normally tightly interwoven-if I am sure that it is going to rain, I will take an umbrella-therefore, it is difficult to understand their interplay. Stimulated by the ego-dystonic nature of obsessive-compulsive disorder (OCD), where compulsive actions are recognized as disproportionate, we hypothesized that action and confidence might be independently updated during learning. Participants completed a predictive-inference task designed to identify how action and confidence evolve in response to surprising changes in the environment. While OCD patients (like controls) correctly updated their confidence according to changes in the environment, their actions (unlike those of controls) mostly disregarded this knowledge. Therefore, OCD patients develop an accurate, internal model of the environment but fail to use it to guide behavior. Results demonstrated a novel dissociation between confidence and action, suggesting a cognitive architecture whereby confidence estimates can accurately track the statistic of the environment independently from performance.

Concepts: Obsessive–compulsive disorder


Serotonin reuptake inhibitors (SRIs), the first-line pharmacological treatment for obsessive-compulsive disorder (OCD), have two limitations: incomplete symptom relief and 2-3 months lag time before clinically meaningful improvement. New medications with faster onset are needed. Because converging evidence suggests a role for the glutamate system in the pathophysiology of OCD, we tested whether a single dose of ketamine, a non-competitive N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, could achieve rapid anti-obsessional effects. In a randomized, double-blind, placebo-controlled, crossover design, drug-free OCD adults (n=15) with near constant obsessions received two 40-minute intravenous infusions, one of saline and one of ketamine (0.5 mg/kg), spaced at least 1 week apart. The OCD visual analogue scale (OCD-VAS) and the Yale Brown Obsessive-Compulsive Scale (YBOCS) were used to assess OCD symptoms. Unexpectedly, ketamine’s effects within the crossover design showed significant (p<0.005) carryover effects (ie, lasting longer than 1 week). As a result, only the first-phase data were used in additional analyses. Specifically, those receiving ketamine (n=8) reported significant improvement in obsessions (measured by OCD-VAS) during the infusion compared with subjects receiving placebo (n=7). One week post-infusion, 50% of those receiving ketamine (n=8) met criteria for treatment response (35% Y-BOCS reduction) versus 0% of those receiving placebo (n=7). Rapid anti-OCD effects from a single intravenous dose of ketamine can persist for at least one week in some OCD patients with constant intrusive thoughts. This is the first randomized, controlled trial to demonstrate that a drug affecting glutamate neurotransmission can reduce OCD symptoms without the presence of an SRI and is consistent with a glutamatergic hypothesis of OCD.Neuropsychopharmacology accepted article preview online, 19 June 2013; doi:10.1038/npp.2013.150.

Concepts: Pharmacology, Clinical trial, Crossover study, Receptor antagonist, NMDA receptor, Fluvoxamine, Selective serotonin reuptake inhibitor, Obsessive–compulsive disorder


Body dysmorphic disorder (BDD) is a debilitating disorder characterized by an excessive pre-occupation with an imagined or very slight defect in one’s physical appearance. Despite the overall success of cognitive behavioural therapy (CBT) in treating BDD, some people do not seem to benefit as much from this approach. Those with high overvalued ideation (OVI), for instance, have been shown to not respond well with CBT. The purpose of this study was to evaluate the efficacy of an inference-based therapy (IBT) in treating BDD. IBT is a cognitive intervention that was first developed for obsessive-compulsive disorder with high OVI, but whose focus on beliefs can also apply to a BDD population. IBT conceptualizes BDD obsessions (e.g., ‘I feel like my head is deformed’) as idiosyncratic inferences arrived at through inductive reasoning processes. Such primary inferences represent the starting point of obsessional doubt and the treatment focuses on addressing the faulty inferences that maintain the doubt. Thirteen BDD participants, of whom 10 completed, underwent a 20-week IBT for BDD. The participants improved significantly over the course of therapy, with large diminutions in BDD and depressive symptoms. OVI also decreased throughout therapy and was not found to be related to reduction in BDD symptoms. Although a controlled-trial comparing CBT with IBT is needed, it is proposed that IBT constitutes a promising treatment alternative for BDD especially in cases where OVI is high. Copyright © 2011 John Wiley & Sons, Ltd. KEY PRACTITIONER MESSAGE: An inference-based therapy (IBT) may be effective in treating BDD. Unlike CBT, in IBT, overvalued ideation does not appear to negatively impact decrease in BDD symptomatology.

Concepts: Psychology, Cognitive behavioral therapy, Logic, Reasoning, Body dysmorphic disorder, Inductive reasoning, Deductive reasoning, Obsessive–compulsive disorder