Background: Current US mental disorder prevalence estimates have limited usefulness for service planning and are often discrepant. Data on clinical significance from the National Institute of Mental Health Epidemiologic Catchment Area Program (ECA) and the National Comorbidity Survey (NCS) were used to produce revised estimates, for more accurate projections of treatment need and further explication of rate discrepancies.
Methods: To ascertain the prevalence of clinically significant mental disorders in each survey, responses to questions on life interference from, telling a professional about, or using medication for symptoms were applied to cases meeting symptom criteria in the ECA (n = 20,861) and NCS (n = 8098). A revised national prevalence estimate was made by selecting the lower estimate of the 2 surveys for each diagnostic category, accounting for comorbidity, and combining categories.
Results: Using data on clinical significance lowered the past-year prevalence rates of "any disorder" among 18- to 54-year-olds by 17% in the ECA and 32% in the NCS. For adults older than 18 years, the revised estimate for any disorder was 18.5%. Using the clinical significance criterion reduced disparities between estimates in the 2 surveys. Validity of the criterion was supported by associations with disabilities and suicidal behavior.
Conclusions: Establishing the clinical significance of disorders in the community is crucial for estimating treatment need. More work should be done in defining and operationalizing clinical significance, and characterizing the utility of clinically significant symptoms in determining treatment need even when some criteria of the disorder are not met. Discrepancies in ECA and NCS results are largely due to methodologic differences.