Although stuttering has long been acknowledged as a familial disorder, the nature of a genetic component remains unclear. Most previous data used in genetic studies were obtained primarily from adults who stutter and may be biased in several respects. The purpose of this investigation was to quantify the frequency of stuttering in relatives of preschool-age children who stutter, and who were first seen close to the onset of the disorder. Detailed pedigrees (family trees), including first-, second-, and third-degree relatives, were obtained from parents of 69 children who stuttered. We found, as have previous studies, that more male than female relatives ever stuttered, but that female subjects who stuttered had more female relatives who ever stuttered than did male subjects. In order to identify the genetic model most consistent with the observed patterns of stuttering transmission, we conducted segregation analyses. Results from these analyses suggest that transmission of a single major genetic locus increasing the liability to stuttering best accounts for the transmission of stuttering in families of preschool-age children who stutter.
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