Diagnosis is assessed through levels of intelligent and adaptive behavior.
Intelligence is the ability to learn, think, solve problems and make sense of the world, this is also known as intellectual functioning. They asses this through an IQ test. The average being 100. Those scoring below 100, even to 75 are often but not always mentally disabled. Other facts can play in to yield low IQ scores (depression, anxiety, lack of effort) and is import to factor these in prior to concluding the measured intelligence test when it the person is being deemed "significantly below average."
Adaptive Behavior refers to skills needed to live independently. To measure, professional use the functional capabilities to those of children of similar age. They do so by doing structured interviews by eliciting information from someone in the community who knows them well. Certain skills are important to adaptive behavior, such as
- Daily Living Skills: Getting dressed, going to the bathroom, feeding themselves.
- Communication Skills: What is being said and being able to respond with an answer
- Social Skills: Interacting with peers, family members, adults and others.