BACKGROUND:A recent study reported strong evidence for the involvement of a region on human chromosome 1 and genetic susceptibility to anorexia nervosa (AN). A more detailed analysis of this region has suggested 2 genes that may account for this susceptibility. These data suggest that polymorphisms in both the serotonin 1D (HTR1D) and opioid delta 1 (OPRD1) receptor genes show a significant association with restricting AN (RAN). METHODS:In the current study, we have conducted an independent association study on 226 females meeting DSM-IV criteria for AN and 678 matched volunteers. RESULTS:We genotyped 4 SNPs in HTR1D and 6 SNPs in OPRD1. 3 SNPs were found to be associated with both RAN and binge-purge AN (BPAN) within the gene for OPRD1. We also found evidence of association between 2 polymorphisms within HTR1D and RAN. CONCLUSIONS:These data support the hypothesis that polymorphisms within this region form a component of the genetic basis to susceptibility to RAN. However, further work is required to understand the processes that may be mediated by these genes.