Scientific Studies

person holding a book open

Our work is based on the principles of evidence-based practice. This means that clinical decision making integrates the best available research evidence with clinician judgment and the client's particular needs and values. Each client's response to treatment is continuously tracked, and changes are made as needed.

The effectiveness of the programs offered at ISTAR have been scientifically evaluated, both with older children and adults, and with young children.

Older children, teens + adults

We have conducted several studies to scientifically evaluate the results of therapy with older children, teens and adults. These studies have shown that immediately after therapy almost all clients showed pronounced improvements in fluency, confidence and self-perceptions. When we continued to follow the clients up to 5 years after therapy, taking careful measurements of their speech and attitudes, we found that the majority maintained significant levels of improvement. Of those who did not maintain, some returned to pre-treatment levels of stuttering while others retained some improvement.

The following reports and studies of ISTAR's programs have been published in peer reviewed scientific journals. If you would like reprints of these publications, please contact us at

  • Langevin, M., Kully, D., Teshima, S., Hagler, P., & Prasad, N. N. G. (2010). Five-year longitudinal treatment outcomes of the ISTAR Comprehensive Stuttering Program. Journal of Fluency Disorders, 35, 123-140.
  • Teshima, S., Langevin, M., Hagler, P., & Kully, D. (2010). Post-treatment speech naturalness of Comprehensive Stuttering Program clients and differences in ratings among listener groups. Journal of Fluency Disorders, 35, 44-58.
  • Kully, D., Langevin M., & Lomheim, H. (2007). Intensive treatment of stuttering in adolescents and adults. In E. G. Conture & R. F. Curlee (Eds.), Stuttering and related disorders of fluency, 3rd Edition (pp. 213-232). New York: Thieme.
  • Langevin, M., Kully, D. A., & Ross-Harold, B. (2007). The Comprehensive Stuttering Program for School-age Children with strategies for managing teasing and bullying. In E. G. Conture & R. F. Curlee (Eds.), Stuttering and related disorders of fluency, 3rd Edition (pp. 131-149). New York: Thieme.
  • Huinck, W. J., Langevin, M., Kully, D., Graamans, K., Peters, H. F. M., & Hulstijn, W. (2006). The relationship between the pre-treatment clinical profile and treatment outcome in an integrated stuttering program. Journal of Fluency Disorders, 31, 43-63.
  • Langevin, M., Huinck, W., Kully, D., Peters, H. F. M., Lomheim, H., & Tellers, M. (2006). A cross-cultural, long-term outcome evaluation of the ISTAR Comprehensive Stuttering Program across Dutch and Canadian adults who stutter. Journal of Fluency Disorders, 31, 229-256.
  • Langevin, M., & Kully, D. (2004). Longitudinal treatment outcome: Four case studies. In A. Packman, A. Meltzer, & H. F. M. Peters (Eds.), Theory, research and therapy in fluency disorders, Proceedings of the Fourth World Congress on Fluency Disorders (pp. 195-203). Montreal, Canada: Nijmegen University Press.
  • Kully, D. & Langevin, M. (1999). Intensive treatment for stuttering adolescents. In R. F. Curlee (Ed.), Stuttering and Related Disorders of Fluency. (2nd ed.) pp139-159. Thieme: New York.
  • Langevin, M. & Boberg, E. (1996). Results of intensive stuttering therapy with adults who clutter and stutter. Journal of Fluency Disorders, 21, 315-327.
  • Boberg, E., & Kully, D. (1994). Long term results of an intensive treatment program for adults and adolescents who stutter. Journal of Speech and Hearing Research, 37, 1050-1059.
  • Langevin, M., & Boberg, E. (1993). Results of an intensive stuttering therapy program. Journal of Speech-Language Pathology and Audiology, 17,158-166.
  • Kully, D. & Boberg, E. (1991). Therapy for school-aged children. In W.H. Perkins (Ed.), Seminars in Speech and Language, 12 (4), 291-300.

For a complete list of books, book chapters and articles, see publications.

Young children

When appropriate treatment is provided early, stuttering is often reduced to minimal or very mild levels. Many parents report that their children enjoy the treatment and become more talkative and outgoing.

At ISTAR, treatment for preschoolers often begins with the Lidcombe Program. Developed in Australia, the program has been comprehensively tested and shown to be effective in the long term. In cases when the Lidcombe Program is not the optimal approach, we design treatment programs based on research and our own experience working with preschool children who stutter.

Following is a selection of studies on the effectiveness of the Lidcombe Program:

  • Jones, M., Onslow, M., Packman, A., Williams, S., Ormond, T., Schwarz, T., & Gebski, V. (2005). A randomized controlled trial of the Lidcombe Programme of early stuttering intervention. British Medical Journal. (doi:10.1136/bmj.38520.451840.E0) (published Aug. 11, 2005).
  • Lincoln, M. A., & Onslow, M. (1997). Long-term outcome of early intervention for stuttering. American Journal of Speech-Language Pathology, 6, 51-58.
  • Lincoln, M., Onslow, M., Lewis, C., & Wilson, L. (1996). A clinical trial of an operant treatment for school-age children who stutter. American Journal of Speech-Language Pathology, 5, 73-85.
  • Lincoln, M. A., Onslow, M., & Reed, V. (1997). Social validity of the treatment outcomes of an early intervention program for stuttering. American Journal of Speech-Language Pathology, 6, 77-84.