THE GENETIC-BASIS OF PERSISTENCE AND RECOVERY IN STUTTERING

Although past research has provided evidence of a genetic component to the transmission of susceptibility to stuttering, the relationship be tween the genetic component to stuttering and persistence and recovery in the disorder has remained unclear. In an attempt to characterize t his relationship, the immediate and extended families of 66 stuttering children were investigated to determine frequencies of cases of persi stent and recovered stuttering. Pedigree analysis and segregation anal ysis were used to examine patterns of transmission. The following ques tions were investigated: 1. Is there a sex effect in recovery From stu ttering? Here, we sought to test the hypothesis that Females are more likely to recover than males, leading to the change in sex ratio from approximately 2:1 males to females close to onset of the disorder, to 4 or 5:1 in adulthood. 2. Is persistence/recovery in stuttering transm itted in families? If recovery/persistence appears to be transmitted, (a) are recovered and persistent stuttering independent disorders?; (b ) is recovery a genetically milder form of persistent stuttering?; or (c) is persistence/recovery transmitted independent of the primary sus ceptibility to stuttering? Results indicated sharply different sex rat ios of persistent versus recovered stutterers in that recovery among f emales is more frequent than among males. It was found that recovery o r persistence is indeed transmitted, and Further, that recovery does n ot appear to be a generically milder form of stuttering, nor do the tw o types of stuttering appear to be genetically independent disorders. Data are most consistent with the hypothesis that persistent and recov ered stuttering possess a common genetic etiology, and that persistenc e is, in part, due to additional genetic factors. Segregation analyses supported these conclusions and provided statistical evidence For bot h a single major locus and polygenic component for persistent and reco vered stuttering.