mental illness

noun

variants or mental disorder or less commonly mental disease

: any of a broad range of medical conditions (such as major depression, schizophrenia, obsessive compulsive disorder, or panic disorder) that are marked primarily by sufficient disorganization of personality, mind, or emotions to impair normal psychological functioning and cause marked distress or disability and that are typically associated with a disruption in normal thinking, feeling, mood, behavior, interpersonal interactions, or daily functioning

mentally ill adjective

Examples of mental illness in a Sentence

Recent Examples on the Web

That's despite the fact, according to the National Institute of Mental Health (NIMH), 23.1 percent of U.S. adults, or 59.3 million people in 2022, live with some form of mental illness. —Josh Hammer, Newsweek, 23 Dec. 2024

As his behavior increasingly grows erratic, Curtis struggles with whether his warnings of an impending disaster are genuine or the onset of mental illness. —Travis Bean, Forbes, 21 Dec. 2024

Breed was tasked with getting the city through the COVID-19 pandemic, dealing with a surge of drug overdose deaths, rampant homelessness, untreated mental illness, the racial justice protests of 2020, a rise in retail theft, and the collapse of the downtown area’s economy. —Barnini Chakraborty, Washington Examiner - Political News and Conservative Analysis About Congress, the President, and the Federal Government, 13 Dec. 2024

Responding to people with behavioral health disabilities The 2023 DOJ investigation found nearly a quarter of all use-of-force incidents involved people experiencing a behavioral health crisis or had other signs of mental illness. —Connor Giffin, The Courier-Journal, 13 Dec. 2024

Word History

First Known Use

1724, in the meaning defined above

Kids Definition

mental illness

noun

variants or mental disorder

: a medical condition that is marked by a mild to severe disturbance in the way a person thinks, feels, or acts and is usually accompanied by distress and problems functioning in daily activities or interacting with others

mentally ill adjective

Medical Definition

mental illness

noun

variants or mental disorder also mental disease

: any of a broad range of medical conditions (such as major depression, schizophrenia, obsessive compulsive disorder, or panic disorder) that are marked primarily by sufficient disorganization of personality, mind, or emotions to impair normal psychological functioning and cause marked distress or disability and that are typically associated with a disruption in normal thinking, feeling, mood, behavior, interpersonal interactions, or daily functioning

Some homeless families are also hindered by substance abuse and mental illness.

—Ellen L. Bassuk, Scientific American

Catatonia is usually an expression of mental disorders like bipolar disorder or schizophrenia, but it could also come from other medical problems, such as a brain tumor.

—Forrest Wickman, The Pittsburgh Post-Gazette

… mental diseases such as schizophrenia and manic depression may either involve more than one gene or may result from a complex mix of genetic predisposition and environmental rotten luck.

—Natalie Angier, The New York Times Book Review

mentally ill adjective

mentally ill patients

Mental health workers … perform a wide variety of therapeutic, supportive, and preventative functions for persons who are mentally ill and developmentally disabled.

—Barbara M. Swanson, Careers in Health Care

Legal Definition

mental illness

noun

mental ill·​ness

1

: mental disease

2

: a mental condition marked primarily by sufficient disorganization of personality, mind, and emotions to seriously impair the normal psychological and often social functioning of the individual

called also mental disorder