Purpose: A low-activity variant of a polymorphism in the transcriptional control region of the serotonin (serotonin, 5-HT) transporter transporter (5-HTTLPR) has been correlated with neuroticism or avoidance in only a few studies but not all. The authors analyzed the effect of 5-HTTLPR on PDs. METHODS: Patients with PDs (N=320) and healthy volunteers (N=281) were surveyed using the Revised NEO Personality Questionnaire and the 3-D Personality Questionnaire. For all subjects the genotype of 5-HTTLPR was determined. RESULTS: No differences in the genotype distribution of 5-HTTLPR were seen between group C and group B PDs and controls. In contrast, among patients with a clade C diagnosis, those carrying the 5-HTTLPR low-activity short-arm allele showed higher neuroticism scores than non-carriers. CONCLUSION: These results suggest that overall 5-HTTLPR is not associated with anxiety-related traits; different clinical subgroups may have different genetic effects and/or gene-environment interactions.