Intellectual disabilities (ID) are marked by notable limitations in both intellectual functioning and adaptive behavior, impacting the necessary conceptual, social, and practical skills required for everyday life. The causes of ID are varied and include genetic conditions such as Down syndrome, prenatal issues like fetal alcohol syndrome, birth complications such as oxygen deprivation, and early childhood health problems including malnutrition or diseases. Diagnosing ID typically involves thorough evaluations by healthcare professionals, utilizing standardized tests to assess intellectual functioning and adaptive behavior.

Individuals with ID are classified into four severity levels: mild, moderate, severe, and profound, which are based on the level of support they require. Those with mild ID may develop social and communication skills and reach an academic proficiency level comparable to a sixth-grade student, though they may need help with complex tasks. People with moderate ID can perform simple tasks under supervision and benefit from vocational training. Individuals with severe ID have limited communication skills and require substantial assistance with daily living activities, while those with profound ID often have additional sensory or physical impairments and need intensive support.