Interllectual Disability
Three Core Diagnostic Criteria
According to official clinical manuals like the AAIDD and the DSM-5, a diagnosis requires meeting three specific criteria
Intellectual Functioning Deficits
Limitations in mental tools like reasoning, problem-solving, planning and abstract thinking. This is typically measured via standardised testing, with a full-scale IQ score generally sitting around 70 to 75 or below.
Adaptive Behavior Deficits
Ignificant difficulties executing practical, age-appropriate skills necessary for community life.
Early Onset
The condition must manifest during childhood or adolescence, specifically before the age of 22.
Key Areas of Adaptive Behavior
Adaptive behaviors are the collection of conceptual, social and practical skills that people use to function in their daily lives.
Conceptual Skills
Language proficiency, reading, writing, math concepts, time management and money processing.
Social Skills
Interpersonal communication, empathy, social problem-solving, ability to make friends and exercising social judgment.
Practical Skills
Personal self-care (eating, dressing, showering), workplace skills, household tasks, healthcare decisions and using public transport.
Four Levels of Severity
Rather than strictly looking at an IQ score, clinical standards measure severity based on the level of daily support an individual needs to succeed.
Mild
Represents roughly 85% of cases. Individuals can communicate effectively, live independently or in a lightly supervised setting and work regular jobs but may need guidance on complicated legal or medical decisions.
Moderate
Comprises about 10% of cases. Individuals communicate using slightly simpler language and can take care of basic needs with training but they usually require ongoing support to live and work safely in group home environments.
Severe
Making up about 5% of cases. Individuals communicate through basic words, phrases or physical gestures. They require daily, continuous support for their health, safety and self-care.
Profound
Around 1% of cases. Individuals express themselves primarily through nonverbal methods (facial expressions, physical motions) and rely completely on lifelong nursing care and assistance for all aspects of physical life.
Common Causes
An intellectual disability can result from any condition that disrupts typical brain development. However, the exact medical cause remains unknown for many individuals. Common causes include
Genetic Conditions
Abnormalities such as Down syndrome, Fragile X syndrome or Prader-Willi syndrome.
Pregnancy Complications
Prenatal exposure to alcohol, recreational drugs, environmental toxins or maternal infections.
Birth Complications
Severe lack of oxygen (hypoxia) during birth or extreme premature delivery.
Childhood Illnesses
Severe brain trauma or early childhood infections like meningitis, measles or whooping cough