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To the Editor:—
Pedigree or family studies of stuttering have shown increased risks among relatives, but they have not distinguished between the importance of genetic and shared environmental influences. Twin studies that are free of ascertainment bias can distinguish between these causes, but previous twin studies on clinical samples have properly not sought to distinguish. We report data from a large nonclinical sample of twins that are consistent with a model in which 71% of the variance in liability to stuttering was attributed to additive genetic variance. An alternative model positing familial aggregation due to individual and shared family environment did not fit the data.Stuttering is a developmental disorder of speech motor control not related to neurosis or emotional disorder in either the parent or child.1 Ideopathic stuttering begins between ages 2 and 12 years, is more common in males (sex ratio, 2.4:1), and is familial.2,3 Two
Genetic Factors in Stuttering Confirmed. Arch Gen Psychiatry. 1991;48(11):1034-1035. doi:10.1001/archpsyc.1991.01810350074012