Schizophrenia: One of several brain diseases whose symptoms may include loss of personality (flat affect), agitation, catatonia, confusion, psychosis, unusual behavior, and social withdrawal. The illness usually begins in early adulthood. The cause of schizophrenia is not known, but there appear to be both genetic (inherited) and environmental components to the disease. Schizophrenia is not caused by abuse or poor parenting practices. Treatment involves use of neuroleptic medication and supportive interpersonal therapy. The prognosis is fairly good, with two-thirds of those diagnosed recovering significantly.