Intellectual disability is more common among boys than among girls

Background People with intellectual disability (ID) are the largest single disability group. The diagnostic criteria of ID have remained the same for over 50 years.

Method We used the statistical database of the national insurance institution of Finland and determined the number of individuals aged less than 15 years, who received disability allowance due to an ID diagnosis. Autism spectrum disorder, epilepsy and cerebral palsy are frequent comorbidities in people with ID. We also determined the number of individuals aged less than 15 years, who received disability allowance due to these diagnoses recorded by ICD-10 codes.

Results ID was almost two times more common as a cause of disability allowance among boys than among girls. Autism spectrum disorder as a co-morbid diagnosis to ID was almost four times more common among boys than among girls.

Discussion In the X-chromosome, there are several genes affecting intelligence. Still, only part of the male predominance in ID is caused by X-chromosomal genes. We suppose that gene-gene and gene-environment interactions play a role in creating this sex difference which needs to be studied further.

Maria Arvio, Jaana Lähdetie