Intellectual disability rates among male prison inmates.

While only a small percentage of people with intellectual disabilities are responsible for criminal behaviors, the literature points to their overrepresentation in prisons, although not enough attention has been paid to intellectual disability data for inmates. We retrieved studies - in English, Spanish, Italian or French and indexed in Medline between 2000 and 2018 - that provided intellectual disability data for prisons collected by the administration of validated tests to male inmates. Identified were 13 studies involving more than 15,000 inmates referring to intellectual disability and borderline intellectual disability. The general findings of our review corroborate the overrepresentation of people with ID in prisons, although prevalence rates range widely, from as low as 1% to as high as 69.9% (p<0.000001), reflecting to differences in methodology, in local, social and cultural factors and in judicial procedures. Published studies clearly underline the overrepresentation of people with intellectual disabilities in prisons, differences between countries, the vulnerabilities of persons with intellectual disabilities and the need for proper assessment and management policies in prisons worldwide.