Obsessive-compulsive disorder（OCD）is characterized as significant impairment of cognitive-behavioral inhibition,which is causally associated with cognitive processes evoking anxiety, along with increased desire for perfect control over the possible harm, at least in typical OCD patients who have compulsions in response to obsessions. However, OCD has been well conceptualized as a multidimensional and heterogeneous disorder apparently comprising a number of potentially valid subtypes. For example, OCD can be diagnosed by either obsessions or compulsions, and a certain type of OCD patient has only compulsions in response to rules that must be applied rigidly. They often become stuck as a result of rigid rules in every step of their daily working and social life.This type of compulsive behavior is often triggered by specific sensory phenomena such as sight,touch,or personal expression（e.g. need to express himself precisely in written or spoken words）. Thus, such OCD patients usually perform their compulsions in order to relieve sensory phenomena such as feelings of incompleteness and urges to reach a specific sensation of feeling “just right”, and are less likely to have obsessions or cognitive processes preceding the repetitive behaviors.This type of OCD has also been characterized as “tic-related”and tends to have comorbid conditions such as tic disorders, ADHD or skin picking. Indeed, there are some crucial and significant differences in the psychopathology, phenomenology, and putative biological bases between OCD patients with obsession-related compulsions（cognitive type）and those with compulsions repeated according to rigid rules（motoric type）.
 Because of the substantial heterogeneity of OCD, it seems to be beyond the traditional learning model in which anxiety-driven obsessions entrain neutralizing compulsions and also beyond the essential features of anxiety disorders commonly characterized by psychopathological characteristics such as marked and persistent fear,expectant anxiety,fear conditioning, avoidance, and cognitive process to evoke anxiety et al. Eventually, it has caused dramatic changes of view on the core psychopathology of OCD that is based on “preoccupation” and “repeated behaviors”as a failure of behavioral（cognitive and motor）inhibition, which also constitutes a key characteristic of obsessive-compulsive and related disorders （OCRDs）in process of the revision of DSM-5. The precise nature and compass of this spectrum remains to be fully elucidated,but a preliminary approach emphasizes that putative OCRDs have phenomenological （e.g. repetitive thoughts or behaviors）, etiological, psychobiological or treatment overlap with OCD, differentiating OCD from other anxiety disorders.
 Therefore,OCRDs, including OCD,may be classified apart from other anxiety disorders in the revisions of DSM-5 or ICD-11. Nevertheless, recent neuroimaging evidence points to the critical involvement of the lateral and medial orbitofrontal cortices, the dorsal anterior cingulate cortex and amygdalo-cortical circuitry, in addition to cortico-striatal circuitry, in the pathophysiology of OCD, suggesting the possibility that fear extinction, in addition to behavioral inhibition, might be impaired in OCD similarly to other anxiety disorders. Moreover, studies have investigated the relevant neurocircuitry, neurochemistry, and neuroendocrinology commonly underlying depression, anxiety disorders and OCRDs, and have explored the underlying genetic basis of and relevant intermediate phenotypes for developing these conditions.Thus more research is needed to elucidate the essential relationships among these disorders and to validate the future diagnostic classifications of anxiety disorders.