Psychosis is defined as a range of perceptual presentations, with the associated symptoms frequently referred to 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.[1] One study found that there was a high prevalence of trauma in patients with severe mental illness.[25] However, only a small percentage had been diagnosed with PTSD when displaying PTSD-like symptoms.