Oxford Textbook of the Psychiatry of Intellectual Disability 2020

Intellectual Disability (ID) describes a lifelong condition of heterogeneous aetiology, associated with the impairment of intellectual functioning (IQ < 70), significant impairment of adaptive skills, and onset before the age of 18 years. People with ID experience significant physical and mental health problems like associated sensory/motor impairments and epilepsy, some of which are contributed to by underlying primary causes. Psychiatric problems are also three
times more common in people with ID in comparison to the general population