What Causes a Lisp in Children and Adults?

A lisp is a speech sound disorder that most often affects S and Z sounds. Most lisps involve pushing your tongue forward when saying S or letting air escape from the sides of your tongue. This makes S sound like TH or slushy.

Many lisps have no single identifiable cause. Some lisping comes from the way you first learned the sound. Others relate to the shape of your tongue and teeth, hearing, or dental work.

In a 2012 national survey, about 1 in 14 US children ages 3-17 had a voice, speech, or language disorder in the past year.¹ Understanding the types of lisps will help you decide whether to wait it out or see a speech-language pathologist (SLP).

What Causes a Lisp?

Many speech sound disorders have no known cause, but physical, hearing, and nerve/muscle problems can make S and Z harder to say.

Learning S and Z the Wrong Way

Often there is no physical reason for a speech sound disorder. Children may have learned to say S by putting their tongue too far forward, and the habit stuck.

Tongue Tie and Tongue Thrust

With tongue tie, or ankyloglossia, a tight band under the tongue limits how high it lifts. A consensus statement from ear, nose and throat specialists says it doesn’t usually affect speech.³ Evidence that releasing it helps speech is limited, so see an SLP first.

Tongue thrust is when you push your tongue against your front teeth or let it stick out between them when you swallow or rest. It often goes along with a frontal lisp and an open bite. Myofunctional therapy can help tongue thrust, but it won’t replace speech therapy for the S sound.

How the Teeth and Jaws Line Up

Your front teeth help shape airflow when saying S and Z. If your bite and jaw aren’t aligned properly, that can change where your tongue sits and how air flows. Some dental issues linked to lisps include:

• Open bite (your front teeth don’t meet)
• Overjet (your upper front teeth stick out)
• Gaps between your front teeth
• Missing front teeth

Long-Term Pacifier or Thumb Use

Pacifier use and thumb sucking over several years has been linked to open bite and forward tilting of the front teeth. The American Academy of Pediatric Dentistry recommends that both habits stop by age 3.⁵ However, evidence that pacifier use leads to speech issues is limited.

Hearing Loss and Developmental Conditions

Conditions that can come with a lisp include:

• Hearing loss, or fluid in the ears from repeated infections
• Cleft palate (an opening in the roof of your mouth)
• Childhood Apraxia of Speech (a brain disorder that makes it hard to plan mouth movements)

These don’t explain every lisp, but when one is present, it changes how an SLP evaluates and treats it.

Are Lisps Genetic?

Speech sound disorders tend to run in families, so if your parents or siblings have speech or language issues, you are more likely to as well.

The Four Types of Lisps

Lisps are named by where your tongue sits and where the air escapes.

Frontal Lisp

Also known as an “interdental lisp,” this lisp is common in young children, and many grow out of it. The tip of the tongue pushes forward between the front teeth when saying S and Z, making it sound like TH, so “zoo” would sound like “thoo.”

Dental Lisp

With a dental lisp, the tongue tip presses against the front teeth rather than behind them. S sounds muffled, much like a frontal lisp, but the tongue stays hidden.

Lateral Lisp

Air escapes over the sides of your tongue when saying S, making it sound wet and slushy. Z, SH, CH, and J sounds are often affected as well.

Palatal Lisp

The middle of the tongue touches the roof of the mouth (your palate) when saying S and Z. They often sound muffled or like “hy.”

Do Children Outgrow a Lisp?

Many children outgrow a frontal or dental lisp. At ages 4 to 5, children say most sounds correctly but may still be working on a few, such as S, Z, SH, CH and TH.⁷

However, lateral lisps are not a normal part of speech development and usually require speech therapy to correct. If your child has a lateral or palatal lisp, have it evaluated as soon as you notice it.

What Causes a Lisp in Adults?

Most people who lisp have had it since they were children. A new lisp can follow a change in your mouth. Possible causes include:

• Orthodontic appliances: braces, retainers or palate expanders. Lingual braces, which sit behind the teeth, may be more likely to cause a lisp.
• Dental work: new dentures, or a crown, veneer or bridge on your front teeth.

Speech changes from braces, retainers or palate expanders often go away after a few weeks. However, your S sounds may stay a bit off for more than 3 months.⁸

See a doctor soon for new or worsening speech changes with no clear dental cause.

If your speech is suddenly slurred or difficult to understand, call 911 right away. Don’t assume this is just a lisp, because it may be a sign of a stroke. Even if it’s the only symptom, don’t wait to see if it goes away.

A droopy face or a lopsided smile is another stroke symptom.

How Speech Therapy Treats a Lisp

An SLP will look in your mouth, listen to you talk and may test your hearing. Speech therapy can help young children say sounds more clearly, though the evidence is stronger for some approaches than others.¹⁰

Speech therapy for lisps usually has five stages, plus practice at home:

1. Hearing the difference: Telling a normal S from a lisped S
2. Placing the tongue: Finding the right spot with a mirror and hand cues
3. Words: Practicing S at the start, middle and end of words
4. Phrases and sentences: Practicing until the sound is reliable
5. Conversation: Using the sound in everyday talk

Non-Speech Exercises Lack Strong Evidence

Some people advertise “exercises” to fix a lisp, such as tongue “push-ups,” blowing or sucking through a straw. A Cochrane review found no strong evidence that these non-speech exercises helped improve lisps, even when added to speech therapy.¹¹

Coping With a Lisp

Lisping doesn’t cause any physical problems, but a lisp that lasts is linked to low self-esteem and a higher risk of bullying. These steps can help:

• Start therapy: Speech therapists work with people of all ages. Over time, therapy can help you feel more confident.
• Get support: Ask a counselor or therapist to help your child deal with teasing.
• Set boundaries: Ask people not to imitate your speech or joke about your lisp.

When to See a Speech-Language Pathologist or Dentist

See an SLP for a lisp that started in childhood. Your child’s school or pediatrician can arrange an evaluation. For new or worsening speech changes with no clear dental cause, see a doctor first, and call 911 if they come on suddenly.

A dentist or orthodontist helps when the teeth, bite, a tongue tie or a dental appliance is part of the cause. Sometimes an orthodontist treats an open bite before the SLP works on the lisp.

Call 911 for Sudden Speech Changes

Call 911 right away if speech suddenly becomes slurred or hard to understand, even if it’s the only sign.⁹ Also call for any of these sudden signs:

• Drooping, numbness or weakness on one side of the face
• Numbness or weakness in an arm or leg, especially on one side
• Confusion or trouble understanding speech
• Trouble seeing, trouble walking, dizziness or loss of balance
• A severe headache with no known cause

Don’t drive to the hospital or have someone drive you, because an ambulance crew can start care on the way.

Signs It’s Time for a Speech Evaluation

By ages 4 to 5, most children say most consonants correctly and are easy to understand.¹² See an SLP if:

• Your child still lisps around age 5
• It sounds wet, slushy or muffled, which suggests a lateral or palatal lisp, at any age
• Speech is hard to understand, or other sounds are affected
• Your child is upset, avoids talking or gets teased
• You have concerns about your child’s hearing
• You’re an adult who wants to change a lifelong lisp

Reasons to See a Dentist or Orthodontist

Book a dental visit if:

• A lisp from braces, a retainer, dentures or other dental work isn’t improving
• The front teeth don’t meet, stick out or have a wide gap
• The tongue looks tied down or won’t lift well
• A thumb or pacifier habit continues past age 3

To find a certified SLP, search ASHA’s ProFind directory.