Subtypes of panic attacks and ICD-9 classification.

No single ICD-9 category corresponds to panic disorder (DSM-III). To investigate whether patients with panic attacks can be identified by means of ICD-9, 97 patients with three panic attacks within 3 weeks were recruited from various medical centers, and were classified independently according to DSM-III and ICD-9. The ICD-9 diagnoses were scattered over a broad range of categories, and it was impossible to identify patients with panic disorder in this manner. Anxiety state, affective psychosis, and depressive neurosis were the most frequent ICD-9 diagnoses. The boundary between affective psychosis on the one hand and anxiety state and depressive neurosis on the other hand was validated by present and previous symptomatology and by cluster analysis. The boundary between anxiety state and depressive neurosis could not be validated in this way. Correspondingly, modifications of the ICD-9 classifications are proposed.