Under the infinitesimal model, SNPs affecting heritability of OCD (or any trait) should be scattered randomly across chromosomes, so that heritability per chromosome should track with chromosome length. This is observed in our study (Figure 2) and there is a significant correlation between heritability per chromosome and length (r = 0.55, p-value = 0.008). Chromosome 13 had the lowest heritability, significantly lower than what would be expected under the uniform distribution model.
