Severe disturbances of thought, emotions, and behaviors characterize schizophrenia.

Individuals may think and speak in illogical fragments that are very disorganized. They may also have delusions, beliefs that exist despite evidence to the contrary, such as the belief (a paranoid delusion) that they are being followed by the director of the Central Intelligence Agency.

Hallucinations are prevalent among individuals with schizophrenia and refer to seeing, hearing, feeling, tasting, or smelling things that are not there, such as hearing the voice of Abraham Lincoln. Other symptoms include unusual motions or immobility, extreme lack of energy or emotional response, and inappropriate affect, such as laughing when hearing about the death of a friend.