Short answers, pulled from the story.
A mental disorder, also called a mental illness, mental health condition, or psychiatric disability, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. The DSM-5 of 2013 defines it as a syndrome marked by clinically significant disturbance in a person's cognition, emotion regulation, or behavior.
Mental disorders are common. In most countries more than one in three people report sufficient criteria for at least one at some point in their life, and in the United States 46 percent qualify at some point. A 2005 review of 16 European countries found that 27 percent of adults are affected within a 12-month period.
Two widely established systems classify mental disorders: the International Classification of Diseases produced by the WHO, with the ICD-11 in effect since the 1st of January 2022, and the Diagnostic and Statistical Manual of Mental Disorders produced by the American Psychiatric Association since 1952, with the DSM-5-TR released in 2022. Both list categories of disorder and provide standardized diagnostic criteria.
In 2019, major depression affected about 264 million people, dementia about 50 million, bipolar disorder about 45 million, and schizophrenia and other psychoses about 20 million. Unipolar depressive disorder is the third leading cause of disability worldwide, accounting for 65.5 million years lost.
Treatment and support are provided in psychiatric hospitals, clinics, or community mental health services. Common options include psychotherapy such as cognitive behavioral therapy and psychiatric medication including antidepressants, anxiolytics, mood stabilizers, antipsychotics, and stimulants, alongside lifestyle changes, social interventions, peer support, and self-help.
Critics including Paula Caplan and Allen Frances argue that psychiatric diagnosis relies on fallible subjective judgments rather than objective biological tests. In 2013 Frances wrote that diagnosis still relies exclusively on fallible subjective judgments, and a 2002 British Medical Journal editorial warned of inappropriate medicalization leading to disease mongering.