Schizophrenia is a severe and disabling mental disorder that affects a person's thought processes and ability to interact with others. It typically develops during adolescence or young adulthood and symptoms include hallucinations, delusions, and disordered thinking. While the exact causes are unknown, schizophrenia is thought to involve genetic and neurological factors. Effective treatment involves medication and psychotherapy to help manage symptoms and allow people to lead functional lives. Famous individuals who suffered from schizophrenia include Abraham Lincoln's wife and mathematician John Forbes Nash.