A mental disorder or mental illness is a psychological or behavioral pattern that occurs in an individual and is thought to cause distress or disability that is not expected as part of normal development or culture. Definitions, assessments, and classifications of mental disorders can vary. Categories of diagnoses in these schemes may include:
dissociative disorders
mood disorders
anxiety disorders
psychotic disorders
eating disorders
developmental disorders
personality disorders, and many other categories.
In many cases there is no single accepted or consistent cause of mental disorders, although they are often explained in terms of a diathesis-stress model and biopsychosocial model. Mental disorders have been found to be common, with over a third of people in most countries reporting sufficient criteria at some point in their life. Mental health professionals diagnose individuals using different methodologies, often relying on case history and interview.
