The etiology of multisomatoform disorder (MSD) is largely unknown, but an influence of genetic factors is likely. Since pain is a major component of MSD and dopamine as well as serotonin are involved in pain pathways, genes of the dopaminergic and serotonergic system are promising candidate genes and we assumed that polymorphisms could be associated with MSD. One hundred forty-nine patients with MSD and 149 age- and gender-matched healthy controls participated in this study. DNA from all participants was genotyped for 22 single nucleotide polymorphisms (SNPs) within genes of the dopaminergic and serotonergic system by polymerase chain reaction, a restriction enzyme analysis, and pyrosequencing. The distribution of SNP alleles, genotypes, and haplotypes was compared between patients and controls. Neither an allelic nor a genotypic association was found for any individual SNP, but testing for a haplotypic association revealed that a haplotype of the serotonergic genes HT(1B) and HT(1D) indicated a lower risk. However, this statistically insignificant protective effect became highly significant on the background of two DAT1 haplotypes. Interestingly, if these two DAT1 haplotypes are analyzed without considering the serotonergic genes as confounders, they are significantly associated with an enhanced risk. Taking into account observations from recent publications, this apparent contradiction might be explained with the complex interaction of the dopaminergic and serotonergic systems. To conclude, our results reveal an involvement of polymorphisms in dopaminergic and serotonergic genes in the etiology of MSD in patients of German descent, but their exact role in MSD requires further investigation.

The etiology of multisomatoform disorder (MSD) is largely unknown, but genetic disposition may be one of several risk factors. As pain is a major component of MSD, and polymorphisms in the catechol-O-methyltransferase (COMT) gene are associated with COMT enzymatic activity and pain sensitivity, we assumed that COMT polymorphisms could be associated with MSD. One hundred and forty-nine patients with MSD and 149 age- and sex-matched healthy controls participated in this study. The inclusion criteria for MSD were in accordance with the structured clinical interview of the diagnostic and statistical manual of mental disorders IV. DNA from MSD patients and controls was genotyped for six single-nucleotide polymorphisms (SNPs) within the COMT locus by polymerase chain reaction and restriction enzyme analysis. The distribution of COMT SNP alleles, genotypes, and haplotypes was compared between patients and controls. None of the investigated SNPs, including the functionally relevant common SNP in codon 158 (Val158Met), showed a statistically significant allelic, genotypic, or haplotypic association with MSD. We conclude that COMT polymorphisms on their own do not seem to play a relevant role as major genetic risk factors for MSD.