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  • Q&A with Australian Health Practitioners

    Could thumb sucking cause a lisp speech impediment?

    My son is two years old and sucks his thumb. When he says words like ‘Wiggles’ with an ‘S’, it sounds like he has a lisp. Could this be because of his age, he is just started talking, or because of the thumb sucking and is it permanent? Very worried as i dont want him to have a lisp and cant stop the thumb sucking!
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  • 6


    Rachel Tosh

    Speech Pathologist

    Rachel is a speech pathologist specialising in speech, language, literacy and feeding therapy with more than 10 years of experience. Her aim is to help … View Profile

    Thumb sucking has been associated with speech difficulties in some studies but the exact nature of the relationship is still unclear (eg does thumb sucking cause speech problems or are children at risk of speech problems more likely to be thumb suckers).  Certainly in my clinical experience I have seen a number of children who are/were thumb suckers and have a lisp. It depends on the type of lisp he is showing.

    There are two primary types of lisp. The first is what they call and interdental lisp which is basically making a “th” sound instead of the “s” sound so that the word ‘sun’ sounds like ‘thun’. This type of lisp is not concerning for a two year old. The other type of lisp called a lateral lisp is when the air is released over the sides of the tongue instead of through the centre of the tongue (lateral means side/s). This type of lisp sounds distorted and slushy. You can make the same sound yourself to get an idea of what it sounds like by trying to make a “s” sound with the tip of your tongue stuck up behind your top teeth. This type of lisp is never normal in a child and it is strongly advisable to seek advice from a speech pathologist as soon as possible.

    With any child who sucks their thumb or a pacifier it is really important to ensure they don't have anything in their mouth while they are talking. This encourages the development of more normal speech patterns rather than trying to produce speech sounds around an obstruction in their mouth. Encourage your child to withdraw his thumb while he is talking and explain that mummy wants to know what he is saying but it is too hard when he has his thumb in his mouth. It can also be useful to look for potential triggers for thumb sucking behaviours (eg they are often associated with a comfort toy) and try to reduce them (eg by restricting the holding of the toy to bedtime). Hope this information helps.

  • 4


    Sharon Moore

    Speech Pathologist

    I am a Speech Pathologist with 30 years clinical experience, working over the years with a wide range of clients with communication and swallowing disorders. … View Profile

    Thumbsucking is an oral habit that can cause an anterior open bite (space between the upper and lower teeth even with back teeth closed). This creates a space that the tongue likes to ‘sit in’ and move into and if thumbsucking persists, can effect bony growth particularly in the upper jaw: also encouraging undesirable chewing and swallowing habits. It is also related to ‘lisp’ production in speech and can be the cause of a simple lisp perpetuating past the time it would normally resolve on its own. My first recommendation would be to look in detail at the underlying causes/reasons for the thumbsucking, then manage from there. Any Speech Pathologist trained in Oral Myology   can help you work specifically on the thumbsucking. 

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