This study aims to evaluate whether a previously reported association between homozygosity for the 10-repeat allele of the dopamine transporter gene (10/10) and poor response to methylphenidate (MPH) would be replicated in a sample of Brazilian attention deficit/hyperactivity disorder (ADHD) boys. In a blind naturalistic study, 50 male ADHD youths were treated with MPH. Efficacy of the medication was measured by means of the 10-item Conners Abbreviated Rating Scale (ABRS), and the Children's Global Assessment Scale (CGAS). While 75% (15/20) of the youths without 10/10 genotype demonstrated an improvement higher than 50% in the ABRS scores with MPH, only 47% (14/30) of the subjects with 10/10 genotype achieved the same level of improvement with medication (one-tailed P = 0.04). In addition, the group without this genotype had significantly higher increase in the CGAS scores than the other group (one-tailed P < 0.01). Our findings support an association between homozygosity for the 10-repeat allele at dopamine transporter gene locus and poor response to MPH.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.