Obsessive-compulsive disorder spectrum as a scientific "metaphor".

As a result of clinical, epidemiological, neuroimaging, and therapy studies that took place in the late 1980s, obsessive-compulsive disorder (OCD) has been well-characterized in the field of anxiety disorders. Other disorders attracted attention for their similarities to OCD, and were located in the orbit of the disorder. OCD has become known as the "primary domain" of a scientific "metaphor" comprising the putative cluster of OCD-related disorders (OCRDs). It is a "paradigm" with which to explore basal ganglia dysfunction. The OCRDs share common phenomenology, comorbidities, lifetime course, demographics, possible genetics, and frontostriatal dysfunction (particularly caudate hyperactivity.) The adoption of this metaphor analogy has proven useful. However, 15 years since its emergence, the spectrum of obsessive-compulsive disorders remains controversial. Questions under debate include whether OCD is a unitary or split condition, whether it is an anxiety disorder, and whether there exists only one spectrum or several possible spectrums. Further work is needed to clarify obsessive-compulsive symptoms, subtypes, and endophenotypes. There is need to integrate existing databases, better define associated symptom domains, and create a more comprehensive endophenotyping protocol for OCRDs. There is also a need to integrate biological and psychological perspectives, concepts, and data to drive this evolution. By increasing research in this field, the OCD spectrum may evolve from a fragmented level of conceptualization as a "metaphor" to one that is more comprehensive and structured.