Why kids suck their thumbs (and why “just stop” often isn’t enough)

If that sounds like your house, you’re not doing anything wrong. And neither is your child.

I’m Joanne, a myofunctional therapist. Parents often reach out to me about thumb sucking, so I want to explain a little bit about why it happens and what I look at in therapy. The short version: there’s usually a reason the thumb goes in, and it often starts with the tongue.

Four things a healthy mouth does

I always start with four things every human being should be doing, day and night, just to be healthy:

1. Breathing through the nose.
2. Lips together, resting closed.
3. Tongue up, resting on the roof of the mouth, from the tip all the way to the back, with no gap.
4. Swallowing correctly.

For thumb sucking, the one to look at is number three: where the tongue rests.

Why the tongue’s resting spot matters

When the tongue rests up, it touches the roof of the mouth, including a small bump on the gum just behind the two front teeth, called the incisive papilla. That contact is thought to stimulate the vagus nerve, a nerve that helps the body calm down.

Our bodies switch between two modes all day long. One is “rest and digest”: the calm mode we need for eating and sleeping. The other is “fight or flight”: the alert mode for exercise or getting away from danger. A tongue resting up may help the body settle into that calm mode.

Two common reasons the tongue sits low

In my work, I most often see two reasons the tongue doesn’t rest up.

1. The nose isn’t working well for breathing. That could be allergies, large adenoids (tissue at the back of the nose) or large tonsils, a crooked septum (the wall between the two sides of the nose) from an injury or from birth, or something else. The body is smart. If the nose can’t do the job, the mouth opens so you can breathe. Once the lips part, the tongue tends to drop.

When the tongue stays low for a long time, its muscles don’t get used the way they’re meant to. The body starts borrowing other muscles instead: the jaw, the neck, the face.

2. A tongue tie. Everyone has a small piece of tissue under the tongue that connects it to the floor of the mouth. When that tissue is tight or short, the tongue can’t move freely, and it may not be able to reach the roof of the mouth.

So where does the thumb come in?

Here’s the part I most want parents to hear.

When the tongue is low, it isn’t touching the roof of the mouth. So it may not be giving the body that calming signal. But the body still wants to feel safe and settled. So the thumb may go in and press where the tongue would normally rest. In a way, the thumb ends up doing the tongue’s job.

Sucking is one of the first ways babies learn to calm themselves, and studies in babies show it can help them settle. It feels good, and it feels calming, which is why the thumb keeps going back in. Over time, that becomes a habit.

That’s why I say: it’s not your child’s fault. Their body is looking for a calm, safe feeling, and the thumb is the way it has found.

Why “just stop” doesn’t work on its own

This is why telling a child to stop usually isn’t enough. If the reason underneath is still there, the body keeps reaching for the same comfort.

So in therapy, I look for that reason first. Is the nose working? Is your child able to breathe through it? Is there a tongue restriction? Those are two of the things I check, among others.

What myofunctional therapy works on

Once we understand what’s going on, therapy focuses on helping the tongue do its job. The tongue isn’t one muscle. It’s made of eight different muscles, with a set on each side, and each one needs to work. We practice moving the tongue:

• side to side
• lifting up
• curling the sides and the tip
• pushing the middle up and lowering the back
• all without moving the jaw, neck, cheeks, or sometimes even the entire head

The goal is a tongue with the strength and coordination to rest on the roof of the mouth, day and night. If those muscles can’t do the work, it’s very hard for the tongue to stay up while your child sleeps.

A big part of therapy is awareness. Can your child feel the tip of their tongue? The middle? The back? The whole tongue needs to rest up, not just the tip. So we work on unwinding the old habits, building that feeling, and practicing until resting the tongue up starts to feel normal.

Sometimes other providers help too

There are other things that can be involved, too. If breathing through the nose is hard, your child may need to see an ENT (an ear, nose and throat doctor). If there isn’t enough room in the jaw for the tongue to rest, a dentist or orthodontist can help with that part.

If the tissue under the tongue is tight and keeps the tongue from moving freely, a release provider (someone who releases tongue ties) may need to be part of your team.