TDT analysis of the data yielded two polymorphisms that were significantly associated with ADHD (rs2770112-Transmitted: 71 Not Transmitted; 48; rs12861247-Transmitted: 43 Not Transmitted: 21), located towards the 5' end of the gene (P < 0.05).
When haplotype TDT analysis of HTR4 was performed, we further found that the C/G haplotype of the 83097 C>T and 83198 A>G polymorphisms (chi(2)=8.783, P=0.003) and the C/G/C haplotype of these and the -36 C>T polymorphism (chi(2)=5.762, P=0.016) were under-transmitted to probands with ADHD.
Our findings suggest a significant association of ADHD with SNP rs498793 (case-control p = .004, odds ratio [OR] 1.6, 95% confidence interval [CI] 1.15-2.23; transmission disequilibrium test [TDT] p = .014, OR 1.69) in the fatty acid desaturase 2 (FADS2) gene.
The negative TDT finding between DAT1 and DRD4 VNTR polymorphisms and ADHD should be interpreted with caution; partly due to lack of power caused by low heterozygosity in the study population.
This association is particularly pronounced among male ADHD probands without any comorbidity (50 trios, HHRR: chi(2) = 5.128, P = 0.024, df = 1; TDT: chi(2) = 4.558, P = 0.033, df = 1), especially the ADHD-I subtype (32 trios, HHRR: chi(2) = 5.792, P = 0.016, df = 1; TDT: chi(2) = 5.333, P = 0.021, df = 1).