The Brazilian contribution to Attention-Deficit/Hyperactivity Disorder molecular genetics in children and adolescents

Secondhand smoke as a risk factor for attention deficit hyperactivity disorder in children

Background: Attention deficit hyperactivity disorder (ADHD) is recognized as a common childhood psychiatric disorder‏ with a worldwide prevalence estimated at 5%. In Egypt, early exposure of children to smoke occurred due to many causes mainly tobacco use. This exposure is linked to a variety of developmental and behavioral consequences for children. This study aimed to investigate the potential association between secondhand smoke (SHS) exposure and ADHD in children and find the association between the level of exposure to SHS and the degree of ADHD symptoms.Method: Case-control study was done by a random selection of children from the outpatient Clinic of Assiut University Hospital of Children. Data were collected by a questionnaire to evaluate home exposure to SHS and blood sampling for serum cotinine measurement as an indicator of exposure to SHS.Results: Of 70 ADHD children, 62 (88.6%) of them reported home exposure to smoke while only 14 of 30 control children (46.7%) reported home exposure to smoke. The serum cotinine level was insignificantly higher in the ADHD group than the control group.Conclusion: In conclusion, there is a significant association between ADHD in the examined sample of children and exposure to SHS. Serum cotinine is a biomarker reflecting current exposure to SHS but it is not a reliable indicator of past and long-term exposure to SHS.

Dopamine D4 Receptor Gene Polymorphism in a Sample of Egyptian Children With Attention-Deficit Hyperactivity Disorder (ADHD)

This study aimed to detect DRD4 receptor gene polymorphisms in attention-deficit hyperactivity disorder (ADHD) children and to correlate their phenotype-genotype. Fifty children with ADHD were diagnosed by Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, criteria and were subjected to Conners Parent Rating Scale. All cases and controls were subjected to history taking, physical examination, IQ assessment, and dopamine receptor D4 (DRD4) exon 3 genotyping. The 7-repeat allele was present only in controls, whereas 2-repeat allele was present in the ADHD children (heterozygous 2-repeat allele in 16% and homozygous in 26% of cases). Eight percent of cases had homozygous 4-repeat allele vs 28% of controls, whereas 10% of cases had heterozygous 4-repeat allele vs 6% of controls, with its predominance in controls. The 2-repeat and 4-repeat alleles have been associated with more inattention, hyperactivity, and impulsivity phenotypes. In conclusion, children with ADHD had a significant presence of the 2-repeat allele and absence of the 7-repeat allele.

Advances in molecular genetic studies of attention deficit hyperactivity disorder in China

SUMMARY

Attention deficit hyperactivity disorder (ADHD) is a common psychiatric condition in children worldwide that typically includes a combination of symptoms of inattention and hyperactivity/impulsivity. Genetic factors are believed to be important in the development and course of ADHD so many candidate genes studies and genome-wide association studies (GWAS) have been conducted in search of the genetic mechanisms that cause or influence the condition. This review provides an overview of gene association and pharmacogenetic studies of ADHD from mainland China and elsewhere that use Han Chinese samples. To date, studies from China and elsewhere remain inconclusive so future studies need to consider alternative analytic techniques and test new biological hypotheses about the relationship of neurotransmission and neurodevelopment to the onset and course of this disabling condition.