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What is a lisp?

October 10, 2023

A lisp is a type of speech sound disorder characterized by the mispronunciation of sibilant sounds, which are consonant sounds produced by directing a stream of air over the tongue and through a groove in the teeth. The main sibilant sounds in English are:

  • S
  • Z
  • Sh
  • Zh
  • Ch
  • J

Children with a lisp will mispronounce these sounds in one of two ways:

Interdental lisp

With an interdental lisp, the tip of the tongue protrudes between the front teeth during speech. This causes ‘s’ sounds to be pronounced ‘th’ so ‘sun’ becomes ‘thun’. [1]

Lateral lisp

In a lateral lisp, air escapes over the sides of the tongue so ‘s’ sounds become ‘sl’ sounds. ‘Sun’ becomes ‘slun’. A lateral lisp may affect ‘s’, ‘z’, ‘sh’, ‘ch’, and ‘j’ sounds. [2]


There are several possible causes of a lisp:

  • Normal speech development – Many toddlers will naturally go through a stage of lisping as they learn to coordinate the complex mouth movements required for speech. This usually resolves on its own by age 3-4. [1]
  • Dental issues – Gaps between teeth, missing teeth, or misaligned teeth can cause a lisp. Braces may temporarily cause lisping too. [1]
  • Oral structure – Some children may have a tongue-tie or small jaw that makes proper tongue placement difficult. [2]
  • Neurological issues – Conditions like cerebral palsy, hearing impairment, or cleft palate can contribute to speech difficulties. [3]
  • Behavioural habits – Thumb sucking or tongue thrusting can encourage fronted tongue placement. [2]

If the lisp persists past age 3-4 with no dental or structural cause, it is likely a speech sound disorder that requires speech therapy. [1]


A persistent lisp can lead to:

  • Difficulty communicating clearly[3]
  • Frustration, shyness, or embarrassment[4]
  • Teasing from peers[4]
  • Lower self-esteem[4]

This may cause some children to avoid speaking. Early treatment is recommended to prevent any negative social or emotional consequences. [3]


Speech therapy is the main treatment for lisping. A speech-language pathologist will work with the child on:

  • Tongue, lip, and jaw exercises to improve coordination[1]
  • Correct tongue placement for sibilants[2]
  • Practice words, phrases, sentences with target sounds[3]
  • Generalizing sounds to everyday speech[3]

With consistent speech therapy, most children can overcome a lisp. Treatment is easier the earlier it starts. Early intervention for speech issues is recommended whenever possible. [4]


A lisp is a common speech disorder affecting sibilant sounds like ‘s’ and ‘z’. It can be caused by normal development, dental issues, oral structure, or neurological conditions. Persistent lisping should be evaluated by a speech-language pathologist. With consistent speech therapy, a lisp can usually be resolved successfully. Early treatment leads to the best outcomes.


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