Genes de suscetibilidade no transtorno de déficit de atenção e hiperatividade Susceptibility genes in attention/deficit hyperactivity disorder

O transtorno de déficit de atenção e hiperatividade (TDAH) é um dos transtornos mais comuns da infância e adolescência, afetando entre 3% a 6% das crianças em idade escolar. Essa patologia caracteriza-se por sintomas de desatenção, hiperatividade e impulsividade, apresentando ainda uma alta heterogeneidade clínica. Embora as causas precisas do TDAH não estejam esclarecidas, a influência de fatores genéticos é fortemente sugerida pelos estudos epidemiológicos, cujas evidências impulsionaram um grande número de investigações com genes candidatos. Atualmente, apesar da ênfase dada a este tópico, nenhum gene pode ser considerado necessário ou suficiente ao desenvolvimento do TDAH, e a busca de genes que influenciam este processo ainda é o foco de muitas pesquisas. O objetivo desse artigo é, portanto, sumarizar e discutir os principais resultados das pesquisas com genes candidatos no TDAH.<br>Attention-deficit/hyperactivity disorder (ADHD) is one of the most common psychiatric disorders of childhood and adolescence, affecting 3%-6% of school age children. It is characterized by symptoms of inattention, hyperactivity and impulsivity, showing also a high clinical heterogeneity. Although the precise causes of ADHD are unclear, the influence of genetic factors is strongly suggested by epidemiologic studies, that provide evidences for a large number of investigations with candidate genes. Nowadays, despite the great attention driven to this subject, no gene can be considered as necessary or sufficient to the development of ADHD, and the search for genes that affect this process is still the focus of many investigations. Thus, the objective of this paper is to summarize and discuss the main results on the research with possible susceptibility genes for ADHD

No evidence of association between Catechol-O-Methyltransferase (COMT) Val(158)Met genotype and performance on neuropsychological tasks in children with ADHD: a case-control study

Background: Several studies have suggested an association between the functional Val158Met polymorphism in the Catechol-O-Methyltransferase (COMT) gene and neurocognitive performance. Two studies showed that subjects with the low activity Met allele performed better on the Wisconsin Card Sorting Test (WCST) and another study found an effect on processing speed and attention.Methods: We set out to examine the association between the Val158Met polymorphism and performance on neurocognitive tasks including those tapping working memory, attention and speed, impulsiveness and response inhibition in a sample of 124 children with ADHD. Task performance for each genotypic group was compared using analysis of variance.Results: There was no evidence of association with performance on any of the neurocognitive tasks.Conclusions: We conclude that Val158Met COMT genotype is not associated with neurocognitive performance in our sample