Understanding the Criteria for an Intellectual Disability
Still called mental retardation by some publications and organizations, such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), an intellectual ability refers to limitations in intellectual functioning and adaptive behavior. The different types of intellectual disabilities are divided by level of severity. The DSM-IV-TR codes for the different types based on intellectual quotient (IQ). For example, a patient can receive a diagnosis of mild, moderate, severe or profound intellectual impairment. An additional type of intellectual disability is listed in the DSM-IV-TR, “Mental Retardation, Severity Unspecified,” which a clinician will use if she suspects an intellectual disability, but she cannot test that patient with a standardized test, such as the Wechsler Intelligence Scale for Children (WISC).
The National Dissemination Center for Children with Disabilities notes that almost 614,000 children between the ages of 3 and 21 have a type of intellectual disability and require special education classes. However, to be diagnosed with an intellectual disability, a child needs to meet certain criteria for an intellectual disability such as the one outlined by the DSM-IV-TR. As part of the diagnosis for an intellectual disability, the clinician will evaluate the child's functional capacity. An official diagnosis is also needed for the child to receive aid for special education, such as IDEA.
Criteria for an Intellectual Disability: Intelligence and Functional Capacity
In the DSM-IV-TR, there are three criteria for an intellectual disability that a patient needs to meet. Criterion A stipulates that patients need to have “significantly subaverage intellectual functioning,” which is determined by the IQ score. A score of 70 or below fulfills Criterion A. About 87 percent of patients are only slightly slower than average in their learning skills, while 13 percent have an IQ of 50 or below, according to the National Dissemination Center for Children with Disabilities.
Criterion B for a diagnosis of an intellectual disability involves gaging the child's functional capacity. The clinician will look for impairments in the child's adaptive functioning. The American Association on Intellectual and Developmental Disabilities notes that adaptive behavior includes three types of skills: practical skills, conceptual skills and social skills. When assessing practical skills, the clinician will looks to see if the patient can take care of herself, use money or a telephone, and other daily activities. Conceptual skills include language, number concepts and self-direction. The social skills aspect of an assessment of an intellectual disability and functional capacity involves self-esteem, following rules and interpersonal skills. To assess these adaptive functioning skills, the clinician will use a different test than the one used to evaluate the patient's intelligence level.
Criterion C is the last of the criteria for an intellectual disability. For a patient to be diagnosed with an intellectual disability, these symptoms must have started before the patient was 18 years old.
American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision. American Psychiatric Publishing
National Dissemination Center for Children with Disabilities: Intellectual Disability (formerly Mental Retardation)
American Association on Intellectual and Developmental Disabilities: FAQ on Intellectual Disability