What is the minimum standard deviation (SD) deficit for diagnosing Intellectual Disability?

The correct answer is that a minimum standard deviation deficit of 2 SD below the mean is required for diagnosing Intellectual Disability. This standard aligns with the criteria established by the American Psychiatric Association in the DSM-5.

In this framework, a score that falls 2 standard deviations below the average IQ score, which is set at a mean of 100 with a standard deviation of 15, corresponds to an IQ of approximately 70 or lower. This cutoff is significant because it helps in identifying individuals who may have substantial limitations in intellectual functioning along with concurrent deficits in adaptive functioning—a critical aspect of the diagnosis.

Additionally, the dual requirement of having lower intellectual capacity (i.e., the IQ score) and challenges in adaptive functioning is crucial for accurately diagnosing Intellectual Disability. This approach ensures that the diagnosis is based on both cognitive and functional criteria, reflecting the necessary support and intervention needs of the individual.