Drs. Baillargeon and Penn Reply

To the Editor: Dr. Pinta raises an important point regarding our investigation, specifically that the prevalence estimates of major psychiatric disorders in the Texas prison system are comparable with general population-based estimates and therefore do not support our assertion of an epidemic of psychiatric disorders in the U.S. prison system. First, because our study cohort was restricted to inmates who were newly incarcerated between September 1, 2006 and August 31, 2007, long-term inmates (who may be slightly more likely to have chronic and serious psychiatric disorders) were under-represented. Our assessment of the entire Texas Department of Criminal Justice prison population (N=234,031) during the same 12-month period yielded prevalence estimates for the following four psychiatric disorders: 1) major depression: 4.2%, 95% confidence interval (CI)=4.1–4.3; 2) bipolar disorder: 2.6%, 95% CI=2.5–2.7; 3) schizophrenia: 1.4%, 95% CI=1.4–1.5; and 4) nonschizophrenia psychotic disorder: 2.4%, 95% CI=2.3–2.5. Overall, 10.6% of inmates had one of these four major psychiatric disorders. These estimates are substantially higher than 12-month general population estimates based on the Epidemiologic Catchment Area study (major depression: 2.7%, bipolar disorder: 0.7%, schizophrenia and schizophreniform disorders: 1.0% [1] ) and the National Comorbidity Survey (manic episode: 1.3%, schizophrenia and other nonaffective psychosis: 0.5% [2] ). In particular, our finding that 3.8% of Texas prison inmates (N=8,893) had a diagnosis of schizophrenia or other psychotic disorder reveals that the prevalence of psychotic disorders is substantially elevated relative to the aforementioned general population-based estimates. Regarding Dr. Pinta’s point that the transfer of patients from state hospitals to prisons should result in significantly higher percentages of inmates diagnosed with psychotic disorders, it is important to consider that given the size of the Texas prison population (for a 12-month period: N=234,031), 2,000 additional inmates with schizophrenia would add less than a single percentage point to the overall 1-year prevalence of schizophrenia.

Our reference to previous reports of serious mental health disorders in 15% to 24% of U.S. inmates (3 – 5) included studies that did not restrict their analyses to the four major psychiatric disorders assessed in our investigation. Thus, inclusion of these references may have been misleading, and we should have referenced a distinct group of studies that employed criteria for serious mental illness that were parallel to our study (e.g., axis I major mental disorder of thought or mood). An assessment of studies that have used diagnostic criteria comparable with that of our study showed that between 10% and 15% of prison inmates have a serious mental illness (6 – 8) . It is important to note that our study likely underestimated the true prevalence of major psychiatric disorder compared with rigorously designed and implemented population-based prevalence studies (1, 2) . However, because the four major psychiatric disorders we evaluated are consistently screened for and treated in the Texas prison system, it is unlikely that these underestimations occurred by a large margin.

Since less severe psychiatric disorders, such as anxiety disorders and axis II disorders, were not rigorously evaluated in the Texas Department of Criminal Justice, we were unable to examine the prevalence of these conditions. We were also unable to access data pertaining to substance use disorder, long reported to be exceedingly high among prison inmates (1, 6, 9) . It will be important for future studies to include assessments of these additional disorders, along with major psychiatric disorders, to reveal the true extent of the mental illness epidemic in U.S. prisons. Nevertheless, current research studies show a substantial elevation of major psychiatric disorders, particularly psychotic disorders, among U.S. prison inmates.