The Negative Impact of Thumb Sucking on Speech Development

Although thumb sucking might be considered a natural stage that babies and young children go through and a perfect round the clock soothing aid, thumb sucking may impact on your child’s oral development, including their speech, if it becomes a habit in the long-term. In 2009 a joint study carried out by researchers in the US and Chile found that children who sucked their thumb for a significant length of time during the day or past the age of three were three times more likely to develop speech problems than children who did not suck their thumb. This is contrary to what had previously been thought that as long as children stopped thumb sucking by the age of six, when they typically get their adult teeth, there should be no interference with normal speech development.

How thumb sucking affects speech

Thumb sucking can impact on the development of speech in a number of ways. Sucking a thumb – or another digit for that matter –means that babies have fewer opportunities to babble and get less practice at forming different shapes with their mouths, which can interfere with the development of the oral motor skills needed for speech. Not only this, but with age, in sucking their thumb children have less chance to talk and interact with the world around them, so have fewer opportunities to practice their language skills, including vocabulary and the structure of sentences. Thumb sucking, as with the use of a pacifier, may increase the likelihood of a middle ear infection and if these occur repeatedly they are a major cause of delays in speech sound. Speech is less likely to be clear when children suck their thumb, as they have something in their mouth while talking, hindering their mouth and tongue from making the necessary movements. The repeated action of putting their thumb inside their mouth means that a child’s tongue is pushed backwards, causing it to be bunched up at the back of their mouth.

With time, this has a negative impact on tongue position and its movement, even at times when the thumb isn’t in their mouth. This encourages a child’s tongue to move forward and protrude between their teeth during speech, which can interfere with sound production. In this instance, lisping is more likely, with children struggling to produce S and Z sounds; they also may have difficulty in lifting their tongue to produce L and R sounds. As with a pacifier if children suck their thumb after the age of three years, doing so can push their teeth out of alignment, which can lead to disordered speech sounds. Not only can this happen, but the development of the jaw bone can also be affected by thumb sucking, which in itself can impact of speech.

The solution

If a speech and language assessment shows that a child is not pronouncing speech sounds as they should be at their age, a speech therapist can work with them to help with the particular speech sounds that they have trouble with. It is also possible that the speech therapist may show affected children some oral motor therapy exercises to help improve their tongue strength and position, allowing the problems that thumb sucking has caused for the tongue muscles to be resolved. However, like everything prevention is better than cure, so it is better to nip the thumb sucking in the bud to prevent it causing any speech problems in the first place; certainly make sure your child is not sucking their thumb by their third birthday, as after this stage it is more likely to be detrimental towards their speech..