insane

Insane is an adjective with multiple senses. In everyday language it can describe someone experiencing severe mental illness or someone behaving in an extremely irrational, dangerous, or illogical way. Historically, the term was used more broadly in medicine and law to refer to a wide range of mental states, not all of which would meet contemporary clinical definitions.

Etymology and historical usage explain the broad sense of the word. Insane comes from the Latin insanus, meaning not healthy, from in- “not” and sanus “healthy.” In English, the form and sense evolved over centuries, and in modern medical and legal contexts the term has largely shifted toward more precise language or specific diagnoses. As a result, many professionals avoid the term except in quotation or historical discussion, to reduce stigma and ambiguity.

Medical versus legal meanings. In psychiatry and psychology, “insane” is not a formal clinical diagnosis; professionals use specific diagnoses such as psychosis, mood disorders with psychotic features, or other mental illnesses. In legal contexts, “insanity” or the insanity defense concerns a defendant’s mental state at the time of a crime and varies by jurisdiction. Tests or standards—such as the M'Naghten Rule or others—determine criminal responsibility, and outcomes may include verdicts like not guilty by reason of insanity or other dispositions.

Cultural usage and stigma. The term remains common in media and everyday speech to describe extraordinary or shocking events, but its use can reinforce stigma toward people with mental health conditions. Contemporary discussions emphasize precise clinical language and respect in describing mental health issues.