SLC6A4 and idiopathic pulmonary arterial hypertension: While studies on SERT allele distributions (LL, LS, SS) in PAH patients compared with the general population have shown no significant differences [40], a meta‐analysis suggests that the LL genotype in the SERT L/S polymorphism may increase the risk of developing IPAH, as individuals with this genotype are at higher risk than those with the SS genotype [41].