DSM-IV and ICD-10 generalized anxiety disorder: discrepant diagnoses and associated disability

Background: It is commonly assumed that diagnoses according to DSM-IV and I CD-10 are equivalent. Recent discussions on generalized anxiety disorder (G AD) have suggested that ICD-10 criteria may be identifying a milder form of the disorder than DSM-IV. This report examines prevalence and associated d isability of DSM-IV and ICD-10 GAD. Methods: The Composite International Di agnostic Interview was administered to a community sample of 10,641 people, and the diagnostic criteria that contributed to discrepancies between DSM- IV and ICD-10 GAD were identified. A multiple linear regression analysis wa s carried out to determine the strength of the relationship between disabil ity, as measured by the SF-12, and discrepant diagnoses of GAD. Results: Th e concordance between DSM-IV and ICD-10 GAD was fair (kappa = 0.39). The tw o sources of discrepancy when DSM-IV was positive and ICD-10 was negative r esulted from the requirement in ICD-10 that the respondent endorse symptoms of autonomic arousal (ICD-10 criterion B) and the requirement that ICD-10 GAD does not co-occur with panic/agoraphobia, social phobia or obsessive-co mpulsive disorder (ICD-10 criterion C). The two major sources of discrepanc y when ICD-10 was positive and DSM-IV was negative resulted from the requir ement in DSM-IV that the worry be excessive (DSM-IV criterion A) and that i t causes clinically significant distress or impairment (DSM-IV criterion E) ; DSM-only GAD cases had significantly higher levels of disability than ICD -only cases of GAD after controlling for demographic variables and the pres ence of comorbid psychiatric disorders. Conclusions: While the prevalence r ates for DSM-IV and ICD-10 GAD are almost identical, these classification s ystems are diagnosing different groups of people.