attention deficit-hyperactivity disorder, autism spectrum disorders and OCD or obsessive-compulsive symptoms [11]. In particular, 33% (14/43) of 22q11.2 deletion subjects meet criteria for OCD and an even higher proportion report obsessive-compulsive symptoms (83%) [12], suggesting that the 22q11.2 locus harbors genes that could predispose to OCD. Other researchers have also noted increased rates of marked obsessive-compulsive symptoms and OCD among patients with 22q11 deletion syndrome, with rates of OCD of 8% (2/25) [13], 10.7% (3/28) [14], and 14% (2/14) [15]. In contrast to the study by Gothelf and colleagues [12], the latter studies did not search systematically for OCD in their patients, which might explain the lower frequency. The COMT gene, coding for the enzyme catechol-O-methyltransferase, responsible for dopamine and norepinephrine inactivation, is one of the prominent candidate genes for susceptibility to mental disorders located in this interval, and is considered a major candidate gene in OCD [16].
