Background. The proposed revisions of the ICD and DSM diagnostic systems have led to increased interest in evaluation of diagnostic criteria. This report focuses on the DSM-IV requirement that episodes of generalized anxiety disorder (GAD) must persist for at least 6 months. Community epidemiological data are used to study the implications of changing this requirement in the range 1–12 months for estimates of prevalence, onset, course, impairment, co-morbidity, associations with parental GAD, and sociodemographic correlates.

Method. Data come from the US National Comorbidity Survey Replication (NCS-R), a US household survey carried out during 2001–2003. Version 3.0 of the WHO Composite International Diagnostic Interview (WMH-CIDI) was used to assess DSM-IV anxiety disorders, mood disorders, substance disorders, and impulse-control disorders.

Results. Lifetime, 12-month, and 30-day prevalence estimates of DSM-IV GAD changed from 6·1%, 2·9%, and 1·8% to 4·2–12·7%, 2·2–5·5%, and 1·6–2·6% when the duration requirement was changed from 6 months to 1–12 months. Cases with episodes of 1–5 months did not differ greatly from those with episodes of [ges ]6 months in onset, persistence, impairment, co-morbidity, parental GAD, or sociodemographic correlates.

Conclusions. A large number of people suffer from a GAD-like syndrome with episodes of <6 months duration. Little basis for excluding these people from a diagnosis is found in the associations examined here.