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 ICD-10 are equivalent. Recent discussions on generalized anxiety disorder (GAD) have suggested that ICD-10 criteria may be identifying a milder form of the disorder than DSM-IV. This report examines prevalence and associated disability of DSM-IV and ICD-10 GAD. Methods: The Composite International Diagnostic 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 was carried out to determine the strength of the relationship between disability, as measured by the SF-12, and discrepant diagnoses of GAD. Results: The concordance between DSM-IV and ICD-10 GAD was fair (kappa = 0.39). The two sources of discrepancy when DSM-IV was positive and ICD-10 was negative resulted 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-compulsive disorder (ICD-10 criterion C). The two major sources of discrepancy when ICD-10 was positive and DSM-IV was negative resulted from the requirement in DSM-IV that the worry be excessive (DSM-IV criterion A) and that it 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 presence of comorbid psychiatric disorders. Conclusions: While the prevalence rates for DSM-IV and ICD-10 GAD are almost identical, these classification systems are diagnosing different groups of people.