At what age do children usually start sucking their thumb? Why do they do it? Why is it such a common habit? by Dr. Laurie Mazzuca, Child and Adolescent Psychologist Thumbsucking is a natural, healthy habit that actually begins in the womb! The same sucking reflex (The Babkin reflex) that allows an infant to nurse […]

At what age do children usually start sucking their thumb? Why do they do it? Why is it such a common habit?

by Dr. Laurie Mazzuca, Child and Adolescent Psychologist
Thumbsucking is a natural, healthy habit that actually begins in the womb! The same sucking reflex (The Babkin reflex) that allows an infant to nurse from his mother’s breast is what inspires him to suck on just about anything that approaches his mouth. Infants learn a lot about their world through sucking, and the act of sucking helps infants feel secure, warm, and happy. Thumbsucking or using a pacifier is very relaxing for infants and allows them to self-soothe when they are feeling overstimulated or uncomfortable.

What could cause a child who was not previously a thumbsucker to suddenly start?


Thumbsucking is an act of self-comfort. A young child who begins to suck his thumb, or intensifies the thumbsucking as he gets older, is trying to gain control over himself and his own feelings of insecurity or discomfort. If a child who did not suck his thumb or use a pacifier during infancy begins to do so during the toddler years, it is usually a sign that the child is feeling more distress, and is trying to cope with that distress. For example, it is not uncommon for toddlers to increase their sucking habits after the birth of a younger sibling, or when they begin school. These changes represent both exciting and stressful events for the child, and the thumbsucking is a way for the child to deal with that stress.

Is a pacifier better than thumb-sucking?


There is no right or wrong answer to this question, scientifically speaking. The answer often lies in what, exactly, is the significance of sucking on a finger or a pacifier for the parents. Different cultures, and different families, view thumbsucking or the use of a pacifier differently. Thus, many parents, without realizing, have very strong beliefs or reactions to one of these two behaviors, and this determines whether or not they encourage their infant to suck on a thumb or a pacifier.

If I were forced to answer this question, I would have to think again about the reason why infants and toddlers suck on things…self-soothing. If we think about it this way, we realize that by sucking, the child is trying to soothe or relax himself, and in that case, the finger is the obvious choice, since the finger is always there! Having easy access to a finger allows a child to exert more control over his own feelings without having to depend on an adult for comfort all the time.

However, I usually recommend that, before choosing whether or not to encourage thumb-sucking or sucking on a pacifier, the parents reflect upon which habit seems more appropriate to them. This is such a controversial issue among parents because most parents are afraid that if they allow a child to suck on a thumb or a pacifier, the child won’t be able to stop when he gets older, and they will require intervention to do so. The scientific research just does not support this belief!

Most infants will show some sucking behavior within the first three weeks of life, and in general, it is nothing to worry about. The overwhelming majority of children will stop sucking their thumbs on their own between the ages of two and four years. The research shows that only about 5% of children will continue to suck their thumb after the age of four. Again, since thumbsucking is a relaxing, comforting habit for young children, they usually stop without any help from parents as they grow, mature, and learn other ways to self-soothe. (How many of your colleagues at work suck their thumbs?!)

I think most parents would be surprised to find out that those children that continue to suck their thumbs after four or five years of age have usually had this habit reinforced by parents or other family members. Try to think of it this way: an infant or young toddler will usually suck his thumb in order to relax. When his parent scolds him for doing so, he may stop doing it right away because he also has a very strong desire to please his parents. However, during this interaction, the distress and discomfort of the child continues to grow, so in most cases, the child will start sucking again as soon as the parents aren’t there to catch him or punish him for it. The child then feels an even greater sense of relief and comfort when he starts sucking on his thumb again. In this way, the more parents scold a child or try to prevent him from sucking, the more they are reinforcing this habit.

For this reason, I often ask parents to evaluate their own feelings and beliefs about thumbsucking vs. using a pacifier. If a parent has a more positive reaction to the pacifier than to the thumb, this means that they will be less likely to make negative comments, scold the child, or get upset when he is sucking. In this case, the pacifier would be a better option. However, if a parent is comfortable allowing an infant or toddler to suck his thumb when he needs to self-soothe, there is no scientific reason why the child should use a pacifier instead.

Can this habit lead to some type of disorder?


In general, no. Until children reach the age of four or five, we (child psychologists) do not consider it to be a problem, and young children who suck their thumbs are not different from children who don’t suck with regard to other developmental or psychological problems. However, once children enter school, thumbsucking can cause some social problems. That is, other children, teachers, and adults often react very negatively when an older child continues to suck his thumb, and this can lead to some social difficulties (e.g. teasing) or problems with self-esteem.

I usually recommend that parents don’t make a big deal out of thumbsucking before children reach this age, since statistically, it is most probable that the child will just stop on his own. Even when a child reaches the age of four or five and is still thumbsucking, he will probably stop once he enters school and he sees that other children are not doing it. However, if a child continues to suck his thumb past the age of five, and parents see that it is beginning to cause some social problems or that the child feels bad about himself for doing it, I recommend that they talk with a child psychologist or developmental pediatrician about the issue. In these cases, it is important to figure out why the child has not grown out of this habit in order to create a plan to help the child stop, and a specialist can usually help parents do just that.

Can thumb-sucking cause dental problems?


Actually, research studies show that thumbsucking usually does not cause any damage to teeth formation, as long as the child stops by the time their permanent teeth begin to form. The frequency and intensity with which a child sucks can make a difference; children who suck on their thumb frequently and intensely, with a lot of force, are more likely to show problems in teeth formation if they continue sucking for many years. However, this is not very common. In fact, research studies suggest that thumbsucking does not affect whether or not a child will need braces when he is older (rather, this is probably related to genetics). In addition, research suggests that the many malformations in the upper teeth are caused by tongue thrust and not thumbsucking. (Tongue thrust is a problem that some children have in which the tongue protrudes through the front teeth while swallowing, speaking, or while the tongue is at rest.)

What is the best way to get a child to stop thumb-sucking?

This is a good question. I always tell parents that the best way to reinforce a habit like this in a child is to tell him not to do it! Again, most kids will stop thumbsucking on their own with no intervention (or interference!) from parents. However, if a parent feels very strongly about stopping this habit, it is better to praise the child for NOT sucking, instead of scolding him or punishing him when they are doing it.
In addition, when an older toddler or child doesn’t seem to be growing out of the habit, it is more convenient for parents to ask themselves what may be going on with the child. Is he anxious? Stressed? Have there been a lot of changes recently? If the answer is yes, it is actually more important to focus on resolving the issues that are causing the child to feel stressed instead of the thumb-sucking.

Should a child be rewarded for not sucking his/her thumb?


Well, again, for infants and young toddlers, it is better not to interfere with this habit, since the majority of kids will stop thumbsucking before they are four years old.
However, if a child reaches four or five and is still sucking on a thumb or pacifier, it is a good idea for parents to talk with the child about the habit. A child who does not want to stop sucking is probably not going to, no matter how many rewards you give him. Before beginning a process to stop thumbsucking, it is important for a child to agree that he wants to try to stop. If a child is collaborating with the parents during the process, it can actually be quite easy to stop thumbsucking. There are some easy behavioral strategies that parents and kids can use to stop thumbsucking once and for all. However, if a parent tries to force a child to stop, it can create a real power struggle between parent and child, and since the child is in control of his finger, parents usually lose this battle! I recommend that parents consult with a child psychologist or specialist before starting this process; with just a little bit of help and advice, it can be much easier than parents think.

Sinews Mulitlingual Therapy Institute

Do you want to get more tips for parents? Check out more at our blog