A mental disorder is an illness with psychological or behavioral manifestations associated with significant distress and impaired functioning caused by biological, social, psychological, genetic, physical, or chemical disturbance. It is measured in terms of deviation from some normative concepts. Each illness has characteristic signs and symptoms.
A. Psychotic. Loss of reality testing with delusions and hallucinations (e.g., schizophrenia)
B. Neurotic. No loss of reality testing; based on mainly intrapsychic conflicts of life events that cause anxiety; symptoms include obsession, phobia, and compulsion.
C. Functional. No known structural damage or clear-cut biological cause to account for impairment.
D. Organic. Illness caused by a specific agent producing a structural change in the brain; usually associated with cognitive impairment, delirium, or dementia (e.g., Pick's disease).
E. Disorders usually diagnosed in infancy, childhood, or adolescence
1. Mental retardation.
2. Learning disorders.
3. Motor skills disorder.
4. Communication disorders.
5. Pervasive developmental disorders. (Autism spectrum disorders)
6. Attention-deficit and disruptive behavior disorders.