Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD .
Speed of processing , set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers .
High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity .
BACKGROUND We review ed systematic ally the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder ( ADHD ) and neuropsychological traits relevant for this disorder .
SNP and haplotype analysis of a novel tryptophan hydroxylase isoform (TPH2) gene provide evidence for association with major depression
Tryptophan hydroxylase ( TPH ) , being the rate-limiting enzyme in the bio synthesis of serotonin plays a major role as c and i date gene in several psychiatric disorders . Recently , a second TPH isoform ( TPH2 ) was identified in mice , which was exclusively present in the brain . In a previous post-mortem study of our own group , we could demonstrate that TPH2 is also expressed in the human brain , but not in peripheral tissues . This is the first report of an association study between polymorphisms in the TPH2 gene and major depression ( MD ) . We performed single-nucleotide polymorphism ( SNP ) , haplotype and linkage disequlibrium studies on 300 depressed patients and 265 healthy controls with 10 SNPs in the TPH2 gene .  Significant association was detected between one SNP ( P=0.0012 , global P=0.0051 ) and MD . Haplotype analysis produced additional support for association ( P<0.0001 , global P=0.0001 ) . Our findings provide evidence for an involvement of genetic variants of the TPH2 gene in the pathogenesis of MD and might be a hint on the repeatedly discussed duality of the serotonergic system . These results may open up new research strategies for the analysis of the observed disturbances in the serotonergic system in patients suffering from several other psychiatric disorders
Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD .
Speed of processing , set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers .
High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity .
BACKGROUND We review ed systematic ally the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder ( ADHD ) and neuropsychological traits relevant for this disorder .