Mental health is defined as: a state of successful performance of mental function, resulting in productive activities, fulfilling relationships with other people, and the ability to adapt to change and cope with adversity (US Surgeon General Report, Dec 1999).

Wellness-illness continuum - Dunn's 1961 text, High Level Wellness, altered our concept of health and illness, viewing both as on a continuum that was dynamic and changing, focusing on levels of wellness. Concepts include: totality, uniqueness, energy, self-integration, energy use, and inner/outer worlds.