These obsessions are often accompanied by a profound sense of dread and the urge to complete specific compulsions. Compulsions are repetitive acts, typically

performed a certain number of times or according to certain private rules, that, the individual is driven to complete, even though these acts are perceived as excessive. The Diagnostic and Statistical Manual of Menial Disorders Fourth Edition, Text revision (DSM-IV-TR) 6 and other standard diagnostic classifications, such as the International Classification of Diseases, Tenth Inhibitors,research,lifescience,medical Edition (ICD-10),7 categorize OCD as a unitary nosological entity. While this parsimony has a certain formal appeal, it is misleading. The symptoms used to define OCD are heterogeneous and include various intrusive thoughts and preoccupations, rituals, and compulsions. Two individuals with OCD Inhibitors,research,lifescience,medical may have totally different and nonoverlapping symptom patterns. From as far back as the earliest, descriptions of OCD, investigators have attempted to dissect, the phenotype into homogeneous subtypes. For example, Falret8 made the distinction between “folie du doute” (madness of doubt)

and “délire du toucher” (delirium of touch) in 1869. Most commonly, investigators have distinguished “washers” from “selleck compound checkers.”9-12 Inhibitors,research,lifescience,medical With a few notable exceptions, these attempts had limited success in relating the identified subtypes to biological markers, genetic factors, or treatment response, in part because Inhibitors,research,lifescience,medical pure subtypes of patients are rare, and the recruitment of sufficient sample sizes of each subtype is difficult and impractical. The following review considers an alternative approach to obsessive-compulsive (OC) symptoms.13,14 It begins with an examination of the potential value of a dimensional approach and then considers various potential subtypes of OCD, particularly among early-onset cases. Obsessive-compulsive symptom dimensions The first study to factor-analyze the Yale -Brown Obsessive-Compulsive Scale-Symptom Inhibitors,research,lifescience,medical Checklist (YBOCS-SC)15 was that of Baer.16 He factor-analyzed

the 13 major categories of the Y-BOCS-SC in a sample of 107 patients and identified three factors, accounting for 48% of the variance; these were named “symmetry/ hoarding,” “contamination/cleaning,” and “pure obsessions.” .Following Baer’s seminal work, Leckman and colleagues17 evaluated the same 13 a priori categories used to group types of obsessions and compulsions Astemizole in the YBOCS-SC in two large groups of OCD patients totaling over 300 cases.18,19 In an effort, to identify valid “traits,” they included any OCD symptoms that patients “ever” experienced over the course of their lifetimes, as opposed to limiting these analyses to current symptoms. Remarkably, both data sets yielded nearly identical results. Four factors were identified that in total accounted for >60% of the variance in each data set.