Excerpt: "Although the concept of mental illness is central to the field of mental health and the practice of counseling, there is continuing disagreement about its definition. Several views are widely held. Each has important implications for understanding mental illness, determining which conditions are disorders and who has them, and choosing appropriate approaches to treatment. This controversy involves several important issues."
Bufford, Rodger K., "Models of Mental Illness" (1999). Faculty Publications - Grad School of Clinical Psychology. 295.