Genetics of stuttering: a critical review.

The fact that stuttering runs in families has been documented over a long period and has led to speculations and research about the role of a genetic component to this disorder. Although the genetic factor cannot be proved by familial aggregation and twin studies alone, such research has continued to provide support for a relationship between stuttering and genetics. The purposes of this article are to review and critique the research in this area. The article first assesses research methodologies that have been employed in familial studies of stuttering. It proceeds to review and critique incidence, twin, and aggregation studies. In addition, it includes sections on subgroups, genetic models of stuttering, and implications for future research as well as for clinical work. With a focus on improved methodology and recent findings, a current perspective on our knowledge of the genetic component to stuttering is provided. Among other conclusions, the article emphasizes that failure to consider epidemiologic factors has probably biased previous results regarding the genetics of stuttering. New preliminary data also appear to provide evidence that spontaneous recovery and chronicity are influenced by genetic factors. Generally, however, the review of incidence and twin studies, as well as of evidence for the various inheritance models, confirms previous conclusions about the interaction between genetic and environmental factors in stuttering.