Thumb Sucking Theories

Let me start with this: non-nutritive sucking is a normal part of oral development in infants.

Although many people think that prolonged thumb sucking is just a bad habit, it’s important to consider the other theories behind why it happens.

Here are some of the theories I’ve heard:

  • It simply feels good. Thumb sucking is an analgesic and can provide pain relief.

  • Thumb suckers use the thumb to seal the lips, so they can breathe through the nose.

  • The thumb can be used to prop the mouth open at night to open the airway, pulling the lower jaw and tongue forward.

  • Thumb sucking triggers deeper stages of sleep.

  • Thumb sucking stimulates the palate, which is important for sensory, facial, and cognitive development. (It’s thought that in cases of a tongue tie or little to no breast feeding, the palate is not receiving as much stimulation).

  • Thumb sucking is a habit that persists because of the failure to progress from sucking to chewing in the process of normal motor development.

What do most of these theories have in common? Sleep and breathing. Keep that in the back of your mind for a moment; we’re going to come back to it.

Finger sucking has been associated with dental malocclusions, like the anterior open bite (increased vertical space between upper and lower teeth) and posterior cross bite (cusps of teeth do not come together/overlap properly because of a narrower upper jaw). You can also see a retrognathic profile (pushed back lower jaw) in these individuals. Because sucking habits can cause the upper jaw to become smaller and the lower jaw to be pushed back, the habit can actually create a smaller airway.

Generally speaking, there are four things that contribute to the severity of the malocclusion:

  1. Duration

  2. Frequency

  3. Intensity

  4. Number & positioning of the fingers in the mouth


I find it interesting that (assuming that these theories are accurate), thumb sucking can be used to “open the airway,” but at the same time, the forces from thumb sucking can actually narrow the airway.

It’s a cycle.


If you’re ready to break the cycle, contact us for a fun, affordable, appliance-free habit cessation program.

And as a bonus, we’re not only trained in habit cessation, we’re also trained in general oral function, the promotion of nasal breathing 24/7, and screening for tethered oral tissues (i.e. a tongue tie) and sleep disordered breathing. We can make referrals to appropriate providers, if needed.



Image courtesy of Zohara Nguyen

Image courtesy of Zohara Nguyen