ABSTRACT
OBJECTIVES: In the present study, we investigate the association between homozygosity of the 4-repeat allele (4/4) at the DRD4 and the response to the treatment with MPH in Korean children with ADHD. METHODS: The present study included 71 children with ADHD (8.231.78 years) from two children's psychiatric clinics in South Korea. All drug-naive children with ADHD were treated with MPH for about 8 weeks. The subjects who showed improvement of over 50% compared with the baseline ARS score after 8 weeks of treatment were termed as the 'good response' group. The subjects who showed an improvement of less than 50% were considered as the 'poor response' group. After genotyping for DRD4 were performed, we investigated correlation between homozygosity for 4-repeat allele at DRD4 and the response to MPH treatment. RESULTS: We found that while 79.5% (31/39) of the subjects with homozygosity of 4-repeat allele at DRD4 showed good response to MPH treatment, 68.8% (22/32) of the subjects without homozygosity of 4-repeat allele at DRD4 showed poor response to MPH treatment according to ARS scores assessed by their parents (chi2=16.762, df=1, p<0.01). We also found that while 61.5% (24/39) of the subjects with homozygosity of4-repeat allele at DRD4 showed good response to MPH treatment, 87.5% (28/32) of the subjects without homozygosity of the 4-repeat allele at DRD4 showed poor response to MPH treatment according to ARS scores assessed by their teachers (chi2=17.698, df=1, p<0.01). CONCLUSION: Our findings support an association between the homozygosity of 4-repeat allele and a good response to MPH in ADHD of Koreans.