Bivariate Genetic Analyses of Stuttering and Nonfluency in a Large Sample of 5-Year-Old Twins PurposeBehavioral genetic studies of speech fluency have focused on participants who present with clinical stuttering. Knowledge about genetic influences on the development and regulation of normal speech fluency is limited. The primary aims of this study were to identify the heritability of stuttering and high nonfluency and to assess the ... Article
Article  |   June 01, 2010
Bivariate Genetic Analyses of Stuttering and Nonfluency in a Large Sample of 5-Year-Old Twins
 
Author Affiliations & Notes
  • Catharina Eugenie Maria van Beijsterveldt
    VU University, Amsterdam, the Netherlands
  • Susan Felsenfeld
    Southern Connecticut State University, New Haven and Yale University, New Haven, CT
  • Dorret Irene Boomsma
    VU University, Amsterdam, the Netherlands
  • Contact author: Catharina Eugenie Maria Beijsterveldt, VU University, Department of Biological Psychology, Van der Boechorststraat 1, 1081 BT Amsterdam, the Netherlands. E-mail: toos@psy.vu.nl.
Article Information
Speech, Voice & Prosodic Disorders / Fluency Disorders / Special Populations / Genetic & Congenital Disorders / Speech, Voice & Prosody / Speech
Article   |   June 01, 2010
Bivariate Genetic Analyses of Stuttering and Nonfluency in a Large Sample of 5-Year-Old Twins
Journal of Speech, Language, and Hearing Research, June 2010, Vol. 53, 609-619. doi:10.1044/1092-4388(2009/08-0202)
History: Received September 30, 2008 , Accepted September 28, 2009
 
Journal of Speech, Language, and Hearing Research, June 2010, Vol. 53, 609-619. doi:10.1044/1092-4388(2009/08-0202)
History: Received September 30, 2008; Accepted September 28, 2009
Web of Science® Times Cited: 13

PurposeBehavioral genetic studies of speech fluency have focused on participants who present with clinical stuttering. Knowledge about genetic influences on the development and regulation of normal speech fluency is limited. The primary aims of this study were to identify the heritability of stuttering and high nonfluency and to assess the relative contribution of genetic and environmental factors to the correlation between these 2 fluency phenotypes.

MethodInformation on 6 specific speech fluency behaviors was obtained by maternal report for over 10,500 5-year-old Dutch twin pairs.

ResultsGenetic analyses revealed that both fluency phenotypes were moderately heritable, with heritability estimates of 42% and 45% for probable stuttering and high nonfluency, respectively. Shared environmental factors were also significant, explaining 44% of the individual differences in probable stuttering and 32% in nonfluency. For both phenotypes, the magnitude of the genetic and environmental influences did not differ between boys and girls. The overlap between the 2 traits was substantial (tetrachoric correlation was .72). A bivariate genetic analysis showed that this overlap was due to both overlapping genetic and environmental influences.

ConclusionsThese findings provide a foundation to justify further studies in normal fluency control, a scientific area that has received little cross-disciplinary attention.

Acknowledgments
We would like to thank all parents of the twins in this study for their participation. We gratefully acknowledge support from the Netherlands Organization for Scientific Research (Twin-family database for behavior genetics and genomics studies [I-MagW 480-04-004] and Spinozapremie [NWO/SPI 56-464-14192]).
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