mental illness

American  

noun

mental illnesses plural

1. any of the various forms of psychosis or severe neurosis.

---

mental illness British  

noun

1. any of various disorders in which a person's thoughts, emotions, or behaviour are so abnormal as to cause suffering to himself, herself, or other people

---

mental illness Scientific  

/ mĕn′tl /

1. Any of various psychiatric disorders or diseases, usually characterized by impairment of thought, mood, or behavior.

---

Other Word Forms

Noun Inflected Forms

• mental illnesses
  plural

Etymology

Origin of mental illness

First recorded in 1960–65

Example Sentences

See Examples For:

mental illness

"We already knew psilocybin could be helpful for treating mental illness," Carhart-Harris said.

From Science Daily ● Jul. 22, 2026

When Kean finally reappeared on the House floor this week, he made an emotional, candid speech acknowledging his depression, which many outlets rightly praised as an important step toward destigmatizing mental illness.

From Salon ● Jul. 2, 2026

Financial independence isn’t always possible for everyone, especially when faced with challenges including physical and mental illness.

From MarketWatch ● Jun. 19, 2026

Under the current law, judges must presume mental illness was a factor if a defendant with a legitimate diagnosis seeks diversion.

From Los Angeles Times ● Jun. 18, 2026

Had others been affected with different variants of mental illness?

From "The Gene" by Siddhartha Mukherjee

Related Words

• insanity
• mental disorder