Schizophrenia is a psychiatric diagnosis characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations, delusions, and disorganized thinking. Other symptoms include social withdrawal, decreased emotional expression, and apathy. Symptoms typically come on gradually, begin in young adulthood, and in many cases never resolve. There is no objective diagnostic test; the diagnosis is used to describe observed behavior that may stem from numerous different causes. Besides observed behavior, doctors will also take a history that includes the person's reported experiences, and reports of others familiar with the person, when making a diagnosis. To diagnose someone with schizophrenia, doctors are supposed to confirm that symptoms and functional impairment are present for six months (DSM-5) or one month (ICD-11). Many people with schizophrenia have other mental disorders that often includes an anxiety disorder such as panic disorder, an obsessive–compulsive disorder, or a substance use disorder.