The infrequency of ''pure culture'' diagnoses among the anxiety disorders

Background: Anxiety disorders are known to commonly coexist in individuals, both with other anxiety disorders and with mental disorders from other groupings, such as affective disorders. We questioned how frequently anxiety disorders actually occur in isolation, as ''pure cultures.'' Method: We examined diagnostic patterns among the 711 subjects entered into a large, multicenter study of anxiety disorders, the Harvard/Brown Anxiety Disorders Research Program (HARP), which focused on panic, agoraphobia, generalized anxiety disorder, and social phobias as ''index disorders'' required for intake. Results: We used various definitions for ''pure culture.'' By all definitions, subjects with ''pure culture'' represented a minority, especially in cases of generalized anxiety disorder and social phobia, where comorbidity was virtually ubiquitous. ''Pure culture'' status was associated with later onset of illness and less chronicity. Conclusion: Future studies of anxiety disorders should aim to document the extensive comorbidity, rather than eliminate it by restrictive diagnostic exclusion criteria; lest they yield atypical or even misrepresented groups of patients. Clinicians should not stop at identifying only the ''main'' diagnosis but look for other, comorbid diagnoses that are often present.