Schizophrenia is a serious and lifelong mental disorder that affects 1% of the population worldwide. It is characterized by a range of striking disturbances in mental functioning that are conceptualized as signs and symptoms that can be grouped into discrete categories. These include symptoms of disruption in the experience of reality, such as hallucinations and delusions, which are grouped as positive symptoms. In addition, many patients with schizophrenia show signs of impoverishment in thinking, emotional experience, and social engagement, which are grouped as negative symptoms. A wide range of other signs and symptoms are also observed in this illness, including disorganized thoughts and behaviors, negative mood states, and behavioral impulsivity.