Why Infants Suck Their Thumbs

Dr. Greene's Answer

When Jacques Cousteau first took cameras under water, he opened up an enchanted new world for us to see. When ultrasounds were first turned toward the wombs of pregnant women, an even more marvelous world appeared. Sights that had been hidden for ages were now open to our view, and one of the first things we saw was that babies suck their tiny thumbs even before they are born.

Infants are hard-wired to need and enjoy sucking as a separate experience from feeding. In some infants this need is more pronounced than in others. Infants tend to exhibit the sucking behavior most when they are tired, bored, or in need of comfort. Some babies who do not suck their thumbs can be comforted, stimulated, or put to sleep through pacifier use. This is often more acceptable to parents since they can control the use of pacifiers. The problem with pacifiers is that young babies cannot find them when they fall out of their mouths, which happens quite frequently. Babies who use pacifiers are dependent on an adult who must understand their needs and respond to them. Children who suck their thumbs are able to begin at an early age to meet their own need for sucking. These children fall asleep more easily, are able to put themselves back to sleep at night more easily, and sleep through the night much earlier than infants who do not suck their thumbs.

Many parents are worried that their children won’t stop thumb sucking at the appropriate age. The great majority of children stop thumb sucking spontaneously as they get caught up in learning new skills and no longer need to be stimulated or comforted by sucking. A study by Dr. T. Berry Brazelton indicates that as many as 94% have finished with sucking their thumbs by their first birthdays.

According to the American Dental Association, thumb sucking does not cause permanent problems with the teeth or jaw line, unless it is continued beyond four to five years of age. Many studies have looked at the number of children who continue to suck their thumbs at this time. As it turns out, somewhere between 85% to 99% of children have finished thumb sucking spontaneously before this period (the numbers vary depending on the study). Many parents are concerned that thumb sucking at a late age is a sign of emotional immaturity or lack of self-confidence. When investigators looked at this group for common traits, they found that late thumb suckers had one thing in common that distinguished them from other children — a prolonged history of a strong battle with thumb sucking at an earlier age. It is striking that many well-meaning parents have actually encouraged this behavior by trying to forcibly take the thumb out of their children’s mouths.

For children in the first year of life, sucking to fall asleep or for comfort is self-limiting and wonderful. If they are sucking their thumbs simply because they are bored or are “zoned out,” it is a good idea to distract them by handing them something interesting to hold on to, without even mentioning their thumbs. Until your son is old enough to reason with, any pressure applied against thumb sucking will only turn a natural developmental phase into an ingrained habit.

If your child has not spontaneously stopped thumb sucking by the time he is talking, there are ways to actively encourage him to stop. Right now, however, you do not need to be concerned about your child’s natural way of getting the stimulation and comfort he needs in an independent and healthy way. If you find that the sight of his thumb sucking bothers you, you might want to offer him a pacifier to use until his sucking need diminishes at around 9 months.