Psychosis is a state of mind in which a person loses contact with reality in at least one important respect while not intoxicated with, or withdrawing from, alcohol or drugs, and while not affected by an acute physical illness that better accounts for the symptoms. Common positive symptoms of psychosis include delusions and hallucinations. These symptoms are strongly influenced by the underlying cause of the psychosis: delusions in schizophrenia tend to be bizarre; delusions in depression negative; delusions in mania expansive. When a patient presents with psychotic symptoms, it is important to take a full psychiatric history, perform a mental state examination and complete relevant investigations, as indicated in each individual case.