The APA diagnostic criteria is commonly used to diagnose intellectual disability (ID, formerly mental retardation). As such, the focus leans toward identifying limitations. The AAIDD definition is more often used to develop a rehabilitation plan. It leans toward identifying abilities that facilitate rehabilitation. Diagnosis and rehabilitation are two different but related agendas. The APA definition serves to identify limitations that facilitate diagnosis. In contrast, the AAIDD definition highlights abilities that facilitate rehabilitation.
The APA diagnostic criteria are usually relied upon for that purpose; i.e., diagnosis. In contrast, the AAIDD is relied upon to develop a rehabilitation plan. This plan is called an individualized support plan, or ISP. The ISP identifies the optimal level of support for the person with an ID. This is accomplished by the identifying strengths and functional abilities that can offset deficits. Although limited intellectual and adaptive functioning identify an ID, it is equally important to identify strengths and abilities. Knowledge of these abilities helps to develop the ISP to maximize independent functioning.
For instance, suppose a person with an intellectual disability has good social skills but poor conceptual skills. This information is useful in planning occupational goals. This person might do well as a greeter in a store. Their good social skills mean they can interact well with customers. However, they would be less successful as a cashier, managing money. Both strengths and weaknesses should be documented in an individualized support plan (ISP). Then, individualized supports and interventions can be provided as resources allow. This ensures that persons with disabilities receive the best available care and support. These services maximize their quality of life. ISPs are discussed here.
Intellectual Disability versus Global Developmental Delay
There are two, different, diagnostic terms that are often confused. These are intellectual disability and global developmental delay. A diagnosis of intellectual disability should only be made when mental abilities and adaptive functioning are significantly below average. The term "developmental delay" is reserved for children under the age of five. These children are slow to reach developmental milestones. These milestones include speech and language; social skills; motor skills (sitting walking). However, these developmental delays are insufficient for a diagnosis of intellectual disability. The child might be too young for a full and complete assessment. A child might be unable to complete tests because of their limitations. For instance, certain speech and language limitations make testing difficult. In other words, although children with intellectual disabilities experience developmental delays, not all developmentally delayed children have an intellectual disability.