<qa>  What is schizophrenia characterized by?Schizophrenia is a major mental illness characterized by psychosis, negative symptoms e.g., apathy, social withdrawal, anhedonia, and cognitive impairment. Depression and substance abuse commonly co-occur. These individuals have impaired functioning in the areas of work, school, parenting, self-care, independent living, interpersonal relationships, and leisure time. Among adult psychiatric disorders, schizophrenia is the most disabling, and its treatment accounts for a disproportionate share of mental health services. 