The National Center for Post-Traumatic Stress Disorder

There is growing evidence suggesting that per­ sons with severe mental illness (SMI) are at sharply elevated risk for trauma exposure and for the devel­ opment of PTSD. However, despite almost two decades of published reports and clinical concern, the intersection between traumatic life-events, PTSD, and other severe and persistent mental illnesses (such as schizophrenia or bipolar disorder) remains unclear. Although recent research is beginning to address and clarify these issues, important ques­ tions remain regarding such basic issues as: the magnitude of the association between SMI, trauma exposure, and PTSD; the underlying mechanisms of this association; and implications for the treat­ ment of clients with these comorbidities. Multiple models have been put forth to account for the observed high rates of PTSD in the SMI population. Early traumatic life events may be risk factors for the development of both major depres­ sive disorder and PTSD. SMI may increase the likelihood of trauma exposure through associated correlates like homelessness and substance abuse. In addition, the existence of another major mental illness may increase vulnerability to the develop­ ment of PTSD at any given level of trauma expo­ sure. Research to date supports the likely contribu­ tion of all three of these mechanisms. Several other contributory factors, both real and artifactual, have also been suggested. For example, psychosis may itself represent a Criterion A trauma. In terms of artificially elevated correlation, the potential symp­ tom overlap between depression and PTSD, or schizophrenia and PTSD, may conflate the appar­ ent rates of PTSD in those diagnostic groups (Franklin & Zimmerman, 2001; Priebe et al., 1998). Alternatively, PTSD associated with psychotic symptoms may be misdiagnosed as a primary psy­ chotic disorder (Hamner et al., 2000). Severe mental illness. People with SMI comprise almost 3% of the U.S. population. These individuals are typically long-term, high utilizers of publicly funded mental health services, including inpatient, emergency, and community support. Primary DSM­ IV diagnostic groups comprising the SMI category include schizophrenia, schizoaffective disorder, bi­ polar disorder, and major depression. In addition to diagnostic criteria, the SMI designation also involves chronicity (typically 12-24 months or more, as deter­ mined by individual states) and impairments in functioning (e.g., the ability to work). Until the 1960s and ‘70s, SMI clients were often treated with long-term care in state psychiatric hospitals. Now, deinstitutionalization, the development of anti-psy­ chotic medications, and the availability of commu­ nity support programs allow most SMI clients to have long periods of community tenure. Unfortu­ nately, SMI clients are now vulnerable to multiple risks and co-morbid illnesses in the community, including high rates of poverty, housing instability, homelessness, substance use disorder, blood-borne infections such as HIV, and exposure to violent victimization and PTSD. Rates of trauma exposure and PTSD in the SMI population have not been adequately determined because of nosologic, psychometric, and sampling issues. For example, early reports on trauma and PTSD in the context of serious mental illness fo­ cused on samples that may not have been entirely comprised of SMI as defined above. Some early studies assessed heterogeneous samples of psychi­ atric inpatients, or emergency-room utilizers, who may not have met diagnostic, severity, or chronicity criteria. Other studies of the SMI population only assessed a limited set of possible Criterion A trau­ mas, and most did not employ the CAPS or other “gold standard” assessments for diagnosing PTSD. Prior research suffers from additional limitations, including small sample sizes and single-site studies (for reviews, see Goodman et al., 1997 and Mueser et al., 2002). Since almost all of the studies on this topic have looked at populations in treatment, it is reason­ able to hypothesize that the high rates of PTSD in those seeking psychiatric care for other disorders are partially due to “Berkson’s bias,” or the ten­ dency of people with multiple disorders to seek care more often than those with a single diagnosis, re­ sulting in higher rates of comorbidity in treatment samples than in population samples. Psychometric and differential diagnostic issues. The validity of people’s accounts of traumatic events has