BROOKES, K-J., Neale, B. M., Xu, X., Thapar, A., Gill, M., Langley, K., Hawi, Z., Mill, J., Taylor, E. A., Franke, B., Chen, W., Ebstein, R. P., Buitelaar, J. K., Banaschewski, T., Sonuga-Barke, E. J. S., Manor, I., Miranda, A., Oades, R. D., Roeyers, H., Rothenberger, A., Sergeant, J. A., Steinhausen, H-C., Faraone, S. V. & Asherson, P.
Differential dopamine receptor D4 allele association with ADHD dependent of proband season of birth.
American Journal of Medical Genetics Part B, 147B, 94-99 (2008). DOI: 10.1002/ajmg.b.3056299. [Request a copy] View Article

Introduction: Season of birth (SOB) has been associated with ADHD in 2 existing studies. One further study reported an interaction between SOB & genotypes of the DA D4 receptor (DRD4) gene. -- It is important that these findings are further investigated to confirm or refute the findings.

Methods: We Investigated the eason of birth association with ADHD in 4 independent samples collected for molecular genetic studies of ADHD.

Results:
1 - We found a small but significant increase in summer births compared to a large population control dataset. --

2 - We also observed a significant association with the 7-repeat allele of the DRD4 gene vntr polymorphism in exon 3 with probands born in the winter season, with no significant differential transmission of this allele between summer & winter seasons.

3 - Preferential transmission of the 2-repeat allele to ADHD probands occurred in those who were born during the summer season, -- but did not surpass significance for association, even though the difference in transmission between the two seasons was nominally significant. 5/ However, following adjustment for multiple testing of alleles none of the SOB effects remained significant.

Discussion: We conclude that the DRD4 7-repeat allele is associated with ADHD but there is no association or interaction with season of birth for increased risk for ADHD. Our findings suggest that we can refute a possible effect of season of birth for ADHD.

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