The terms insane, insanity and mentally deranged are commonly used informally to denote mental instability or mental illness but can be considered offensive. The medical profession favors use of the terms mental disorder or psychopathology. In U.S. criminal law, insanity is a legal question, not a medical one. Use mental illness or mental disorder instead of insane or mentally deranged, except in a quote or when referring to a criminal defense.
REFERENCE: NCDJ Style Guide