Psychotic behavior refers to a collection of symptoms that affect the mind, where there has been some loss of contact with reality. People with psychosis typically experience delusions (false beliefs) and hallucinations (seeing or hearing things that others do not), as well as incoherent or nonsense speech and behavior that is inappropriate for the situation. Other symptoms can include trouble thinking clearly and logically, withdrawing socially and spending a lot more time alone, unusual or overly intense ideas, strange feelings, or a lack of feelings, decline in self-care or personal hygiene, disruption of sleep, including difficulty falling asleep and reduced sleep time, difficulty telling reality from fantasy, confused speech or trouble communicating, sudden drop in grades or job performance, emotional disruption, anxiety, lack of motivation, difficulty functioning overall, and mood swings or other mood symptoms, such as depression or mania.

It is important to note that a person will often show changes in their behavior before psychosis develops. Behavioral warning signs for psychosis include suspiciousness, paranoid ideas, or uneasiness with others. In some cases, a person experiencing a psychotic episode may behave in confusing and unpredictable ways and may harm themselves or become threatening or violent toward others. The risk of violence and suicide decreases with treatment.

Psychotic behavior is a common symptom of many mental health conditions, including schizophrenia, bipolar disorder, and brief psychotic disorder. It can also be caused by alcohol and some drugs, brain tumors, brain infections, and stroke. Treatment depends on the cause of the psychosis and might involve drugs to control symptoms and talk therapy. Hospitalization is an option for serious cases where a person might be dangerous to themselves or others.