Comorbidity patterns in routine psychiatric practice: is there evidence of underdetection and underdiagnosis?

The purpose of this study is to present data on the rates of diagnosis and patterns of Axis I comorbidity treated by psychiatrists in routine psychiatric practice, ascertained by practicing psychiatrists, and compare them with those ascertained through structured interview in a national sample of individuals treated in the specialty mental health sector for evidence of underdetection or underdiagnosis of comorbid disorders in routine psychiatric practice.

Data on 2117 psychiatric patients gathered by 754 psychiatrists participating in the 1997 and 1999 American Psychiatric Institute for Research and Education's Practice Research Network's Study of Psychiatric Patients and Treatments (SPPT) were analyzed, assessing psychiatrist-reported rates of Axis I disorders and comorbidities. SPPT data on patients treated by psychiatrists were compared with a clinical subset of patients in the National Comorbidity Survey who had been treated in the specialty mental health sector (SMA).

Rates of comorbidity were higher in the SMA (53.9%) than in the SPPT (31.5%). The prevalence of schizophrenia diagnoses was more than twice as prevalent in the SPPT as in the SMA sample; anxiety disorders were 2 to 22 times more prevalent in the SMA sample. In the SPPT, 4 of the 10 most prevalent comorbid pairs included schizophrenia or bipolar disorder; only one pair in the SMA sample included either diagnoses. Of the 10 most prevalent comorbidity pairings in the SMA sample, 6 included a phobia diagnosis.

Results of these analyses suggest greater differences in the patterns and rates of comorbidities than one might expect between these 2 samples. Possible reasons for these disparities, including methodological differences in diagnostic ascertainment and underdiagnosis of anxiety disorders, are discussed.