The Illinois International Stuttering Research Program

Genetics and Stuttering

To date, no single cause of stuttering has been identified. We do know with increasing certainty, however, that susceptibility to stuttering is genetically transmitted. The notion of genetic involvement originated from both clinical observations and survey findings that the disorder runs in families. Although such evidence is not sufficient for drawing scientific conclusions, later twin and family aggregation studies strengthened the evidence for genetic components to stuttering.

The Illinois International Stuttering Research Program has been extensively involved in the effort to unearth the genetics of stuttering, making major contributions to this domain. Several research directions have been followed:

1. Aggregation studies. These focus on the detailed distribution patterns of stuttering in familial trees (pedigrees), taking into account family size, class of relatives, and gender. Statistical methods such as segregation analyses have been used to find out whether there is a good match between the familial distribution of stuttering and several established genetic models. Our research has also been expanded to identify genetic differences between those who persist in stuttering and those who exhibited early natural recovery.
2. Genetic bases for subtypes. This group of studies is focused on investigation of genetic bases for possible subtypes of stuttering, as reflected in varying phenotypic characteristics such as age of onset of stuttering, disfluency patterns, speech and language skills, motor skills, and temperament.
3. Biological genetics. The main objective at this level of genetic research has been to conduct Linkage Analysis aimed at identifying the general locations of possible genes on each of the 23 chromosomes. To this end, DNA is extracted from blood samples of individual who stutter and members of their families. So far, blood samples have been from the United States, Israel, and Sweden. After DNA is extracted, full genotype analyses are conducted to identify already known (marker) genes on each chromosome. When a marker gene is co-inherited with stuttering beyond chance, it means that the gene(s) contributing to stuttering are on the same chromosome, close to the marker gene.

Send questions and comments to:
Dr. Nicoline Ambrose
Stuttering Research Program
The Department of Speech and Hearing Science
901 S. Sixth St.
Champaign, IL 61820
Phone:217-333-2230