The obsessive-compulsive disorders spectrum concept has grown in recent years because of the common clinical features, such as obsessive thinking and compulsive rituals, biological markers, presumed etiology, and treatment response, that these disorders may share with obsessive-compulsive disorder (OCD). This concept has important implications in regard to diagnosis, nosology, neurobiology, and treatment of a wide group of diverse disorders affecting up to 10% of the population. New insights in central nervous system (CNS) mechanisms that drive the repetitive behaviors of the obsessive-compulsive spectrum disorders have heightened interest in the spectrum in researchers, clinicians, and those involved in drug development.

An important approach in neuropsychiatry centers on employing a dimensional classification of psychopathology. Psychiatric phenomena often fall on a continuum. A dimensional approach allows for the classification of patients who fall at the border of classical entities or who are otherwise atypical. Diagnostic categories are considered along a spectrum if there is considerable overlap in symptoms and in etiology, as demonstrated by familial linkage biological markers, and pharmacological dissection. Categorical and dimensional approaches to the OCD spectrum could have significant implications for diagnosis, nosology, neurobiology, and treatment of a wide group of disorders affecting a sizable percentage of the population.

Recent interest has focused on spectrums in movement disorders, affective disorders, schizophrenia, epileptic and impulsive disorders, and obsessive-compulsive disorders (which we will examine here); in addition, there has been interest in the overlap between these spectrums. Viewing disorders in terms of overlapping spectrums provides researchers and clinicians a framework with which to better understand and treat these disorders.