as either positive or negative. Positive symptoms are delusional, and may include hallucinations, while negative symptoms are characterized by a "lack" of functioning, which may include a lack of affect (emotional feeling) and loss of motivation. One study found that there was a high prevalence of trauma in patients with severe mental illness. However, only a small percentage had been diagnosed with PTSD when displaying PTSD-like symptoms. Therefore, the more complex symptoms of psychosis may prevent the clinical detection required when diagnosing PTSD. In addition, those who have been diagnosed with PTSD and have an identified form of trauma show positive symptoms of psychosis such as delusions and/or hallucinations. Finally, it has been suggested that individuals suffering from psychosis may be more vulnerable to intrusions. References Free will Marcel Proust Memory