Thumb sucking is a common and completely normal behaviour in babies and young children. It often helps children soothe themselves, feel secure, or settle to sleep.
Many parents wonder whether thumb sucking could affect their child’s speech development. While thumb sucking doesn’t directly cause a speech delay, prolonged thumb sucking may influence oral development, which can sometimes affect how speech sounds are produced.
Understanding when thumb sucking is typical—and when it may be time to seek support—can help you make informed decisions for your child’s communication and overall development.
The short answer
Thumb sucking does not directly cause a speech delay. However, if it continues frequently beyond the toddler years, it may contribute to changes in oral and dental development that can influence the way some speech sounds are produced.
If your child is difficult to understand, has persistent speech sound errors, or you are concerned about their communication, a speech pathology assessment can help identify the underlying cause.
Why do children suck their thumbs?
Thumb sucking is a natural reflex that begins before birth.
Many children suck their thumb to:
- Self-soothe
- Feel safe and secure
- Settle to sleep
- Relax when tired or overwhelmed
- Comfort themselves during unfamiliar situations
For most babies and toddlers, thumb sucking is a normal part of development.
Can thumb sucking affect speech?
Thumb sucking itself is not considered a cause of speech or language delay.
However, prolonged or frequent thumb sucking may affect:
- The position of the tongue
- The development of the jaw
- The alignment of the teeth
- The shape of the roof of the mouth (palate)
These changes may make it more difficult for some children to produce certain speech sounds clearly.
Not every child who sucks their thumb will develop speech difficulties, and many children stop naturally without experiencing any long-term effects.
Which speech sounds can be affected?
If prolonged thumb sucking contributes to changes in oral development, some children may have difficulty producing sounds that require precise tongue placement.
These may include:
- S
- Z
- SH
- CH
- J
- TH
Some children may develop a lisp, where air escapes over the tongue during speech, making sounds such as S or Z sound different.
A speech pathologist can determine whether speech sound errors are age-appropriate or whether therapy may be helpful.
Can thumb sucking affect teeth?
Yes.
Prolonged thumb sucking, particularly beyond the preschool years, may contribute to:
- An open bite
- A crossbite
- Teeth moving forwards
- Changes to the shape of the palate
These changes are more likely when thumb sucking is frequent, intense, and continues over a long period.
Your dentist can assess your child’s oral development and advise whether treatment is needed.
When should my child stop sucking their thumb?
Many children naturally stop thumb sucking between 2 and 4 years of age.
If thumb sucking continues beyond this age, families may wish to begin gently encouraging alternative ways to self-soothe.
The earlier the habit reduces, the lower the likelihood of long-term effects on oral and dental development.
Tips to help your child stop thumb sucking
Breaking the habit takes time, and a gentle, supportive approach is usually most successful.
You can try:
- Identifying when your child is most likely to suck their thumb (for example, when tired or bored).
- Offering cuddles, comfort toys or books instead.
- Praising your child when they choose not to suck their thumb.
- Keeping little hands busy with play or craft activities.
- Avoiding punishment or criticism, as this can increase anxiety and make the habit harder to break.
Most children gradually stop with encouragement and support.
When should I see a speech pathologist?
Consider seeking advice if your child:
- Is difficult for unfamiliar people to understand.
- Has persistent speech sound errors.
- Has a noticeable lisp beyond the age when it would typically resolve.
- Becomes frustrated when communicating.
- You are concerned about how thumb sucking may be affecting their speech.
Early assessment can provide reassurance and practical strategies tailored to your child’s individual needs.
How Unified Speech Pathology can help
At Unified Speech Pathology, we assess every child as an individual. If your child has speech sound difficulties, we look at their communication skills, oral motor function and speech development to understand the factors contributing to their speech.
Our evidence-based therapy is tailored to each child’s strengths and goals, and we work closely with families to support clear, confident communication in everyday life.
Frequently Asked Questions
Will thumb sucking cause a speech delay?
No. Thumb sucking is not considered a direct cause of speech or language delay. However, prolonged thumb sucking may influence oral development, which can affect speech sound production in some children.
Can thumb sucking cause a lisp?
In some cases, prolonged thumb sucking may contribute to changes in tongue position or dental alignment that are associated with a lisp. A speech pathologist can assess whether your child’s speech is developing as expected.
Should I stop my toddler from sucking their thumb?
Thumb sucking is a normal self-soothing behaviour in young children. Many children stop naturally. If the habit continues beyond the preschool years or you’re concerned about your child’s teeth or speech, speak with your dentist or a speech pathologist.
Do I need a referral?
No. Speech pathologists are first-contact practitioners, so you can book an assessment without a referral. If you’re eligible for Medicare or NDIS funding, our team can also discuss the funding options available.
References
- Speech Pathology Australia. (n.d.). Communication Milestones. Retrieved from https://www.speechpathologyaustralia.org.au
- Australian Dental Association. (n.d.). Thumb sucking and dummy habits in children. Retrieved from https://www.ada.org.au
- Raising Children Network. (n.d.). Thumb sucking: children. Australian Government supported parenting resource. Retrieved from https://raisingchildren.net.au
- Australian Government Department of Health, Disability and Ageing. (n.d.). Child development and early childhood health. Retrieved from https://www.health.gov.au
- McLeod, S., & Baker, E. (2017). Children’s Speech: An Evidence-Based Approach to Assessment and Intervention. Pearson Australia.
Disclaimer: This article is intended for general educational purposes only and should not replace individual advice from a qualified speech pathologist, dentist or other healthcare professional. If you have concerns about your child’s speech, oral development or thumb sucking habits, seek professional advice.
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