Psychiatric disorders in people with intellectual disability are two to three times more common than in the general population. Estimates of prevalence vary widely depending on sample selection, the definition of psychiatric disorder, which diag­ nostic criteria are used, and the skill and experience of the clinicians. There are many reasons for the higher prevalence of psychiatric disorder in some people with intellectual disability, including neurodevelopmental abnormalities, genetic factors, high rates of epilepsy and other comorbid conditions, personality development, cognitive impairment limiting capacity to cope with stress, and adverse social cir­ cumstances. Table 14.1 lists the risk factors for psychiatric disorder in people with intellectual disability.