Stuttering is an abnormality in speech that affects the rhythm of speech. People who
stutter know what they wish to say, but at the time are unable to say it because of
involuntary repetition, unnecessary lengthening (prolongation), or early stopping
(cessation). This study is designed to increase understanding of the genetic factors that
may relate to stuttering.
Deoxyribonucleic acid (DNA) is a protein found in the nucleus of all cells. It is
responsible for carrying the genetic information of the organism. DNA provides the
directions for making all of the substances in the human body. DNA can be linked together
in small segments called genes. Genes can contain information about anything related to an
In order for researchers to determine what genes are directly related to stuttering they
must conduct several types of studies.
Linkage studies, are studies of families that have a lot of members who stutter from several
generations. The linkage studies will be completed using adult individuals who are
diagnosed as persons who stutter and persons who have never stuttered, from one or more
families with large numbers of family members who have stuttered over several generations.
Candidate gene studies, look closely at genes suspected to be related to stuttering in
patients who may or may not have a significant family history of stuttering.
By conducting these studies, researchers hope to learn more about genes related to
stuttering and ultimately find out what causes stuttering.
Genetic studies in developmental stuttering are important for their potential in ultimately
determining pathophysiological basis of this disorder. This study will combine two
approaches to examine genetic aspects of stuttering, linkage in families, and candidate gene
analysis. Linkage studies will be completed using adult individuals who are diagnosed as
persons who stutter and those who can be judged as never having stuttered from one or more
families with large numbers of affected individuals within several generations. Candidate
gene analyses will also be carried out in adults who stutter to determine if the frequency
of polymorphisms for certain neurotransmitter receptors and enzymes differ from control
populations. In addition, given the heterogeneity of the population of adults who stutter,
other phenotypic probes such as motor skills, language skills, neuropsychological abilities
and psychological responses to stuttering will also be assessed in order to identify
subgroups in which the phenotype expression of the gene may differ.
Subjects must be over the age of 5 and under the age of 90.
Subjects must be in general good health, without evidence of chronic medical illness.
Onset of stuttering in affected individuals must have occurred in childhood (between 3 and
10 years of age), unrelated to psychological or neurological trauma.
Subjects will not be tested for the presence of HIV antibodies. Persons with positive HIV
antibodies will not be excluded, unless they are taking medication which may change their
performance on tasks used for phenotypic assignment.
Subjects will be screened for history of psychiatric illness, such as depression, anxiety
or obsessive-compulsive disorders according to DSM-IV criteria. A history of these
disorders will not disqualify any subject from participation, but will be noted as a
variable in phenotypic assignment.