- Mental health is a level of psychological well-being, or an absence of a mental illness. It is the "psychological state of someone who is functioning at a satisfactory level of emotional and behavioral adjustment". From the perspective of positive psychology or holism, mental health may include an individual's ability to enjoy life, and create a balance between life activities and efforts to achieve psychological resilience.
- According to the World Health Organization, mental health includes "subjective well-being, perceived self-efficacy, autonomy, competence, inter-generational dependence, and self-actualization of one's intellectual and emotional potential, among others." The WHO further states that the well-being of an individual is encompassed in the realization of their abilities, coping with normal stresses of life, productive work and contribution to their community. Cultural differences, subjective assessments, and competing professional theories all affect how "mental health" is defined. A widely accepted definition of health by mental health specialists is psychoanalyst Sigmund Freud's definition: the capacity "to work and to love". It is considered to be a simple and more accurate definition of mental health. 
"Mental health" is the absence of "mental illness." "Mental illness" is the absence of "mental health."
As there is no definitive definition of "mental health," it is impossible to clearly define "mental illness," though mental health professionals, on the basis of a checklist they find available for them in the DSM, will quickly decide whether someone is "mentally ill" or suffers from a "mental disorder."
According to the classifications found in the DSM, there are very few "mentally healthy" individuals in the world.
- Shyness: How Normal Behavior Became a Sickness (book)
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