Thumb sucking is a natural, reflexive behavior that helps infants soothe themselves and learn how to accept nourishment.

The majority of newborns demonstrate thumb, finger, or toe sucking behaviors within hours after birth. Many even sucked their thumbs in utero.

Thumb sucking is common among babies, toddlers, and young children. Many kids who suck their thumbs stop doing so without intervention once they reach school age.

Others respond to mild forms of intervention from their parents.

No specific data exists that indicates how often thumb sucking continues into the teen and adult years. However, anecdotal evidence suggests that there are many adults who suck their thumbs — perhaps as many as 1 in 10.

While most childhood thumb suckers stop on their own, a percentage seem to continue in private for decades. For some, thumb sucking may even be a lifelong habit.

The reasons for this aren’t completely understood. It could be this behavior provides comfort and reduces anxiety for those who do it.

While relatively benign, thumb sucking isn’t without side effects, particularly to dental health.

Adults who suck their thumbs may find that it reduces anxiety and stress, helping them to calm down.

It’s possible that some adults who suck their thumbs experienced trauma during childhood and turned to the behavior to calm themselves down during that time. In some instances, the behavior may simply stick, making for an easy-to-access stress reliever.

Thumb sucking may also become a habit that’s almost involuntary, used to relieve boredom in addition to stress.

There is anecdotal evidence indicating that some people with trichotillomania, a condition earmarked by an irresistible urge to pull out scalp, eyebrow, or body hair, also thumb suck.

Age regression is a condition in which a person displays behaviors more typical of people who are younger than them. Thumb sucking is sometimes associated with this condition.

Thumb sucking doesn’t have many adverse effects in children with baby teeth. However, once permanent teeth come in, thumb sucking may cause problems with tooth alignment.

In adults, problems with bite and oral health may worsen unless they are addressed, either by getting braces or by stopping the behavior.

The side effects of thumb sucking may be more pronounced if you suck your thumb vigorously or often.

Thumb sucking in adults can cause several other side effects:

Misaligned teeth (dental malocclusion)

Thumb sucking can create problems with the proper alignment of teeth, causing conditions such as an overbite to occur.

The upper and lower teeth may also begin to slant outward. This is known as an anterior open bite.

In some instances, the lower incisor teeth may begin to tip toward the tongue.

During vigorous thumb sucking, the cheek muscles flex. This may work to alter jaw shape and cause crossbite, another type of tooth misalignment. Changes to jaw shape can also affect facial appearance.

Changes to the roof of the mouth

Thumb sucking can cause the roof of the mouth to indent and become concave. The roof of the mouth may also become more sensitive to touch and sensation.

Oral infection

Without vigilant hand washing, thumb sucking may introduce dirt and bacteria into the mouth, potentially causing an infection in a tooth or in the gums.

Problems with the thumb

Vigorous or long-term thumb sucking can change the shape of the thumb, making it thinner or elongated.

It can also dry out the skin of the thumb, causing it to crack, bleed, or become infected.

Long-term thumb sucking can also cause callouses to form on the thumb.

Difficulties with speech

The dental problems caused by thumb sucking can result in speech problems, such as lisping.

For some adults who suck their thumbs, stress reduction and alleviation of symptoms stemming from anxiety may be a significant benefit. No other benefits have been identified in either research or anecdotally.

Some adults have reported that they were able to stop sucking their thumbs by making a decision to do so and sticking to it. This may not work for everyone, especially if the behavior has become a long-term or subconscious habit.

Home remedies

If possible, try to identify the triggers in your life that prompt you to suck your thumb. Anticipating when the behavior occurs may help you reduce it by giving you time to substitute stress-relieving techniques, such as deep breathing, meditation, and exercise.

Strategies such as covering your thumb with fabric or with a foul-tasting substance may work.

Keeping your hands busy with a fidget toy or a stress ball may help you to get past the urge.

Other things to try include popping a mint or stick of gum into your mouth when you feel the desire to suck your thumb.

Behavioral therapy

Seeing a mental health professional can provide you with other tools and coping mechanisms. Behavioral therapy has been well documented as discouraging negative activities.

There is no specific data on adult thumb sucking, but it may be more common than people realize.

Like childhood thumb sucking, adult thumb sucking may cause or worsen problems with bite and speech.

If you’re looking to stop thumb sucking, consider talking to your doctor. They may have additional suggestions for helping you quit the habit.