Study investigating the causes of stuttering

New Zealand is participating in an international study that is searching for the genes that cause stuttering.

Researchers are recruiting 1000 New Zealanders who stutter for the largest study of its kind into stuttering that aims to help develop treatments that target the speech disorder's cause, rather than just its symptoms.

Experts from New Zealand, Australia, the UK, US and The Netherlands are recruiting people aged seven and older who stutter, or have a history of stuttering, for the Genetics of Stuttering Study.

The Walter and Eliza Hall Institute of Medical Research (WEHI), Murdoch Children's Research Institute, QIMR Berghofer Medical Research Institute, Griffith University and the University of Melbourne are coordinating the global project.

The University of Otago in Wellington will oversee the New Zealand arm of the study, with support from the Stuttering Treatment and Research Trust in Auckland.

University of Otago Professor Lynette Sadleir said study participants would contribute to a global effort to understand the genetics of stuttering. This could lead to better treatment and potential prevention of the speech disorder, which affects one in 100 New Zealand adults.

"Learning more about the genetic and neurobiological basis of speech and language disorders will help us identify who may be at risk and allow us to develop more targeted treatments," Professor Sadleir said.

Chief study investigator Professor Melanie Bahlo, from WEHI and the University of Melbourne, said stuttering typically emerged in children between two and four years of age, after they had begun to speak.

"Globally, around four per cent of children experience a phase during which they prolong words or get stuck trying to talk," she said.

"Studies show that eight per cent of three-year-olds and 11 per cent of four-year-olds stutter."

Murdoch Children's and University of Melbourne Professor Angela Morgan said although the exact cause of stuttering was unknown, genetics had been found to play a role and researchers had identified four genes that may be linked to stuttering.

"Globally, one per cent of adults stutter and nearly 70 per cent of people who stutter report a family history of the disorder. But even for people who do not have a family history, genetics can still be playing a role," Professor Morgan said.

"Gender is one of the strongest predisposing factors for stuttering. Boys are two to five times more likely to stutter than girls, and are also less likely to recover without therapy.

"Many treatments for speech and language disorders focus on symptoms only, without targeting the underlying cause of the problem. We hope this research will help us better understand the underlying genetic causes of stuttering so we can develop more targeted treatments for people with this speech disorder."

To take part in the trial, volunteers need to complete a 10-minute online survey. Those who meet the study inclusion criteria will be asked to provide a saliva sample for DNA analysis. People who stutter, both with and without a family history, are encouraged to take part.

Participants will be kept informed with fortnightly updates via the study website ( and can follow the Facebook group ( or Twitter ( account for updates.

A parent or guardian must complete the online survey for study participants aged under 16 years.

To sign up for the study, visit the study website (, or for more details email

*The content of this communication is the sole responsibility of MCRI and does not reflect the views of the Australian National Health and Medical Research Council.

Available for interview:

  • Professor Lynette Sadleir, Paediatric Neurologist at the University of Otago in Wellington
  • Janelle Irvine, Executive Director and Clinical Leader – Speech Language Therapy at the Stuttering Treatment and Research Trust
  • Professor Angela Morgan, Murdoch Children's Research Institute
  • Professor Melanie Bahlo, The Walter and Eliza Hall Institute of Medical Research
  • A family with three children who have a stutter (contact Janelle Irvine for details)

Media Contacts:

Bridie Byrne
MCRI communications specialist
+613 9936 6211 / 0427 836 176

Cheryl Norrie
Communications adviser, University of Otago, Wellington
+64 21 249 6787
[email protected]

Professor Lynette Sadleir
University of Otago, Wellington
+ 64 21 997 808
[email protected]

Janelle Irvine
Stuttering Treatment and Research Trust
+64 9 579 6775 / 27 332 8629
[email protected]


The study is funded by an Australian National Health and Medical Research Council grant (APP1160893).