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Retrospective population surveys may underreport mental illness prevalence

One-time retrospective reports appear to regularly underestimate the lifetime incidence of mental disorders, suggesting that mental illness may be substantially more prevalent in the population than previously understood, according to data from the Baltimore Epidemiological Catchment Area Follow-up Study.

The study is a longitudinal, population-based contingent of adults interviewed in four waves beginning in 1981 (wave 1, n=3,481), with follow-up in 1982 (wave 2, n=2,768), 1993 to 1996 (wave 3, n=1,920) and 2004 to 2005 (wave 4, n=1,071). At each wave, trained interviewers gleaned information regarding lifetime history of the following mental disorders: major depressive disorder, obsessive-compulsive disorder, panic disorder, social phobia, alcohol abuse/dependence, and drug abuse or dependence. Patients also were interviewed at each wave about their lifetime prevalence of various physical illnesses, such as hypertension and diabetes.

The researchers estimated lifetime prevalence of mental and physical disorders using the evaluations of lifetime disorders at each wave, over waves 1 through 4 (prospective cumulative), and compared with the lifetime prevalence based only on the reporting of lifetime disorders at wave 4 (cross-sectional retrospective).

The respective lifetime incidence estimates compiled through retrospective and cumulative assessments were 4.5% vs.13.1% for major depressive disorder, 0.6% vs. 7.1% for OCD, 2.5% vs. 6.7% for panic disorder, 12.6% vs. 25.3% for social phobia, 9.1% vs. 25.9% for alcohol abuse or dependence and 6.7% vs. 17.6% for drug abuse or dependence.

Conversely, the retrospective lifetime prevalence estimates of physical disorders were more similar to the cumulative estimates from all four waves: 18.2% vs. 20.2% for diabetes, 48.4% vs. 55.4% for hypertension, 45.8% vs. 54% for arthritis, 5.5% vs. 7.2% for stroke and 8.4% vs. 10.5% for cancer.

According to Wilson M. Compton, MD, MPE, director of the Division of Epidemiology, Services and Prevention Research at the National Institute on Drug Abuse, and author of an accompanying editorial, results from the current study raise an intriguing question as to “whether there is something unique about mental illnesses that make them particularly prone to poor recall compared with identifying physical ailments. Their results suggest that physical conditions are much more consistently reported than mental illnesses.”
Disclosure: The researchers report no relevant financial disclosures.