mental illness

American  

noun

• mental illnesses
  plural

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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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

Frightened that she may be plagued by the same mental illness that felled her mom, Gemma stubbornly refuses to believe anything is wrong.

From Los Angeles Times ● Aug. 21, 2026

Her defence says she was suffering from severe postpartum mental illness, including psychosis, while prosecutors argue she acted deliberately.

From BBC ● Aug. 19, 2026

Miller has not only denied it all in full, he’s been vocal about it, accusing his ex-wife of mental illness and suing her and her lawyer for defamation.

From Slate ● Aug. 1, 2026

But he soon became disillusioned with the psychodynamic account of mental illness advanced by Freudians and looked instead to the brain’s chemistry for answers.

From The Wall Street Journal ● Jul. 28, 2026

Some of them like him and—he thinks—know of mental illness firsthand and so understand him.

From "Vincent and Theo: The Van Gogh Brothers" by Deborah Heiligman

Related Words

• insanity
• mental disorder