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

People with intellectual development disabilities have a higher incidence of mental illness, such as depression and anxiety, due to a range of factors including social stigmatization, difficulty communicating, higher rates of trauma exposure and lack of access to appropriate support systems. —Joseph States, Chicago Tribune, 31 Jan. 2025

Earlier and better mental health care can prevent people with mental illness from being entangled in the justice system at all, Atchity said. —Shelly Bradbury, The Denver Post, 26 Jan. 2025

Undergirding it all are deep thoughts about the expectations society places on women, how men are often seen as the stable ones (but rarely assume the same responsibilities) and where the line between extreme stress and mental illness lies. —Peter Debruge, Variety, 24 Jan. 2025

But are animals actually experiencing mental illness in the way humans do? Questions over the extent to which animals can experience mental illness have existed for centuries. —Mack Degeurin, Popular Science, 15 Jan. 2025

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