caa a22 4500 388096349 CHVBK 20180307125304.0 cr unu---uuuuu 161130e199905 xx s 000 0 eng 10.1017/S109285290001172X doi S109285290001172X pii (NATIONALLICENCE)cambridge-10.1017/S109285290001172X The Genetics of Attention-Deficit/Hyperactivity Disorder [Elektronische Daten] Attention-deficit/hyperactivity disorder (ADHD) has an early childhood onset in the majority of cases. This has a considerable impact on the development of the affected individual, both directly (as a result of the symptoms) and indirectly (through the stresses imposed upon school, learning, socialization, and family life). Several lines of evidence point to a genetic component to ADHD. Family studies show a familial aggregation of ADHD, with a five- to sixfold increase in the incidence of ADHD among first-degree relatives. Twin studies reveal a higher concordance rate for ADHD among monozygotic twins compared with dizygotic twins. To date, molecular genetic research has focused on candidate genes in the dopaminergic system. Genes studied include the D2A1 allele of the dopamine D2 receptor gene, the dopamine transporter gene, and the dopamine D4 receptor gene. One of the major limitations to the study of the genetics of behavioral disorders in children has been the overlap among syndromes, including oppositional defiant disorder, conduct disorder, persistent (adult) ADHD, and bipolar disorder. Future research must address weaknesses in existing studies, including small samples sizes, restricted statistical power, and confounding factors such as comorbid illnesses, clinical heterogeneity with variable symptom severity, and unclear phenotypic boundaries. Copyright © Cambridge University Press 1999 Ram Ranga Schindler Kim M. Bauer Amy Pato Carlos N. Pato Michele T. CNS Spectrums Cambridge University Press 4/5(1999-05), 49-52 1092-8529 4:5<49 1999 4 CNS https://doi.org/10.1017/S109285290001172X text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S109285290001172X text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ram Ranga NATIONALLICENCE 700 1- Schindler Kim M. NATIONALLICENCE 700 1- Bauer Amy NATIONALLICENCE 700 1- Pato Carlos N. NATIONALLICENCE 700 1- Pato Michele T. NATIONALLICENCE 773 0- CNS Spectrums Cambridge University Press 4/5(1999-05), 49-52 1092-8529 4:5<49 1999 4 CNS CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge