The role of the DRD2 C957T polymorphism in neuroticism in persons who stutter and healthy controls.

The present study investigates for the first time the influence of the DRD2 C957T polymorphism on personality in persons who stutter. In a recent study, the CC genotype of this single nucleotide polymorphism has been associated with stuttering, which could not be replicated in a follow-up study. Here, we demonstrate, in N=105 persons who stutter, that carriers of the CC and the CT genotype significantly have the highest neuroticism scores. This shows that the inclusion of personality measures in the investigation of the biological underpinnings of stuttering represents an important new avenue. In healthy control persons, a sex by C+/- allele interaction effect could be demonstrated. Female but not male carriers of the C+ variant report the highest neuroticism scores. Because neuroticism has been reported to be associated with stuttering before, the present data support the idea that this personality trait acts as an endophenotype for stuttering, contributing towards bridging the gap from gene variation to the complex pathology. This idea is supported by an additional path model showing that the polymorphism DRD2 C957T influences the self-reported severity of stuttering mainly by its influence on neuroticism (independent of the variable sex).