Comparing this list with the findings from the other two GWAS, very little overlap is seen (which might be expected, given power limitations of the studies, see below), except for one finding on chromosome 16, which falls into CDH13. As indicated above, this gene was also among the top-findings from both GAIN/IMAGE GWAS studies, as well as many genome-wide studies of addiction related phenotypes, recently reviewed by Uhl et al. (2008a). An additional similarity to be noted is for two TLL genes, TLL1 found among the top-ranks of the analysis based in the categorical ADHD phenotype and showing nominal association in the quantitative analyses by Lasky-Su et al. (see Table V in Lasky-Su et al. 2008b), TLL2 present among the top-30 SNPs in gene regions in the analysis by Lesch et al. Both genes encode metalloproteases that cleave collagen and are expressed in multiple tissues including brain. A specific role in brain development or functioning has not been reported for either of these genes, though. Additional genes modulating the extracellular matrix are found in all three studies, including HAS3 (Lasky-Su
