mental illness

American  

noun

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

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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

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mental illness Scientific  

/ mĕn′tl /

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

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Etymology

Origin of mental illness

First recorded in 1960–65

Example Sentences

President Donald Trump signs a directive to accelerate FDA review of psychedelic drugs for serious mental illness.

From Barron's • Apr. 20, 2026

Carruthers’ case is a perfect storm of capital punishment’s familiar failures: paid informants, information withheld from the jury, untested physical evidence, and the defendant’s mental illness.

From Slate • Apr. 20, 2026

For reasons indistinguishable from mental illness, the U.K. still won’t.

From The Wall Street Journal • Apr. 17, 2026

But Potter, who struggled with unchecked mental illness, depicted himself as an antihero outsider with a spiritual connection to the ravens of Yosemite, and could also be juvenile, selfish and oblivious.

From Los Angeles Times • Apr. 13, 2026

Well, it also took some degree of mental illness, too, but I was suddenly happy for her.

From "The Absolutely True Diary of a Part-Time Indian" by Sherman Alexie

Related Words

• insanity
• mental disorder