INTRODUCTION TO SPECIAL SECTION - MENTAL-RETARDATION AND MENTAL-ILLNESS

Historically, the perceived relation between mental illness and mental retardation has undergone substantial changes. During the past 2 cent uries, clinical observations and systematic research addressing these 2 constructs have developed along separate lines. Consequently, the pa thogenesis and treatment of psychopathology, emotional disorders, and behavior problems experienced by individuals with mental retardation h ave not been the purview of mainstream clinical psychology. This artic le initiates a special section on mental retardation and mental illnes s to provide up-to-date summaries of various key clinical research iss ues regarding this population (i.e., individuals with ''dual diagnoses '').