Association of genes within the major histocompatibility complex with attention deficit hyperactivity disorder.

The objective was to determine whether a relationship exists among the complement C4B gene, a DR region gene and attention deficit hyperactivity disorder (ADHD). Thirty-one subjects with ADHD, their mothers, all but 5 of their fathers, and 90 normal subjects living in northern Utah were studied. DR and C4B typing were performed by serologic HLA typing techniques and the DNA methods PCR-RFLP. The alleles of 2 genes, the null allele of the C4B gene and the beta 1 allele of the DR gene, encode for products involved in immune function and regulation. Each of these alleles was found to be significantly associated with ADHD. Moreover, approximately 55% of the ADHD subjects carried both of these alleles on 1 of their chromosomes, compared to only 8% of normal controls. Genes related to the immune system may be associated with development of the symptoms of ADHD.