<qa>  What is the effect of cognitive behavioral treatment on PTSD?Despite the progress in treating PTSD in the general population and the elevated prevalence of PTSD in people with severe mental illness SMI, there are no empirically validated treatments designed for patients with comorbid PTSD. The cognitive behavioral treatment provided in this study may improve knowledge of PTSD, decrease distorted beliefs, reduce PTSD symptoms, and improve quality of life. 