Archival ReportCatechol-O-Methyltransferase Valine158Methionine Polymorphism Moderates Methylphenidate Effects on Oppositional Symptoms in Boys with Attention-Deficit/Hyperactivity Disorder
Section snippets
Subjects
The sample for this investigation included children and adolescents who were consecutively evaluated for 2 years in the ADHD Outpatient Clinic at the Hospital de Clínicas de Porto Alegre. Inclusion criteria for this investigation were ADHD diagnosis according to DSM-IV criteria, age between 4 and 17 years, European-Brazilian ethnicity as determined by skin color and morphological characteristics, drug-naive for MPH, and prescribed MPH doses of at least .3 mg/kg/day. The diagnoses of ADHD and
Results
The allele frequencies observed were .56 and .44 for Val and Met alleles, respectively. The genotype distributions were consistent with Hardy-Weinberg equilibrium. About 32% of individuals were Val/Val homozygous, 50% were heterozygous, and 18% were Met/Met homozygous.
Table 1 shows demographic and clinical characteristics of patients according to the presence of the Met allele. Genotype/alleles were coded a priori based on functional activity and association with risk of aggressive/antisocial
Discussion
This investigation suggested that ADHD boys with at least one Met allele have a significantly different trajectory of improvement on oppositional symptoms than Val homozygotes when they are treated with MPH. We are unaware of any previous studies investigating the effect of COMT gene specifically in oppositional symptoms in response to methylphenidate treatment.
Although the biological mechanisms to explain our results have not yet been fully determined, we can consider some important points.
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