Seeing beyond the diagnostic and statistical manual: A function-centered review of obsessive-compulsive disorder and anxiety disorders

Obsessive-compulsive disorder (OCD) is classified within its own diagnostic category, separate from anxiety disorders, yet clinical practitioners still treat it as an anxiety disorder; both conceptually and therapeutically. This paper examines the rationale for seperating OCD from the anxiety disorders by contrasting cognitive models of anxiety disorders and OCD, and reviewing phenomenological and psychobiological evidence for OCD's distinctiveness. We compare OCD's behavioral functions with those of specific phobia, panic disorder, agoraphobia, social anxiety disorder, generalized anxiety disorder, and health anxiety disorder. Our review finds no compelling evidence that OCD differs sufficiently from anxiety disorders to warrant its own category. The same functional behaviors are evident in OCD and other anxiety disorders, with the foci of threat being the differentiating factor between disorders (e.g., fear of public speaking vs. fear of contamination in social anxiety and contamination-OCD, respectively). Consequently, we conclude by emphasizing that future research should focus on behavioral function when studying mental disorders, since descriptive similarities may not indicate clinical or functional equivalence. For diagnostic manuals to maintain validity and clinical utility, they must incorporate a functional analytic perspective. Failure to do so may result in inadequate diagnostic categories and stagnant treatment advances (cf. clinical guidelines for OCD have remained unchanged since 2005). While diagnostic manuals are meant to guide treatment selection, descriptive diagnoses need complementary theory-driven case conceptualizations to advance our understanding of maintaining factors and mechanisms of change during treatment. Without this approach, theoretical progress in OCD may stall, ultimately affecting patient outcomes.