['The harmful effects of inbreeding are well known by geneticists, and several studies have already reported cases of intellectual disability caused by recessive variants in consanguineous families. Nevertheless, the effects of inbreeding on the degree of intellectual disability are still poorly investigated. Here, we present a detailed analysis of the homozygosity regions in a cohort of 612 patients with intellectual disabilities of different degrees.', 'We investigated (i) the runs of homozygosity distribution between syndromic and nonsyndromic ID (ii) the effect of runs of homozygosity on the ID degree, using the intelligence quotient score.', 'Our data revealed no significant differences in the first analysis; instead we detected significantly larger runs of homozygosity stretches in severe ID compared to nonsevere ID cases (P = 0.007), together with an increase of the percentage of genome covered by runs of homozygosity (P = 0.03).'] Is excess of runs of homozygosity associated with severe cognitive impairment in intellectual disability?