Loudness dependence of auditory evoked potentials is not associated with polymorphisms or haplotypes in the serotonin transporter gene in a community-based sample of German healthy volunteers

Three previous studies found an association between the loudness dependence (LD) of the auditory evoked potential N1/P2 component, an indicator of central serotonergic neurotransmission, and a functional variation in the promoter region of the 5-hydroxytryptamine transporter (5-HTT) gene (rs4795541 Ins/Del). The results of these three studies were contradictory and possibly biased by the recruitment methods used. We therefore aimed to re-investigate this association (rs4795541) using a community-based sample randomly selected from the general population and to extend the analysis to four further putative variations in this gene (rs3783594, rs3794808, rs140701, rs6354). In this carefully recruited sample, genotypes or haplotypes under investigation were not associated with LD. We speculate that the LD endophenotype depends more on genetic variations in components of the serotonergic system controlling release than on those controlling the uptake mechanism.