It's a hard habit to break, but it can be done. We're talking about the dreaded thumbsucking. Parents - take heart. Eventually, the time is going to come, probably just not soon enough. Research shows that 30 percent of preschool children still suck their thumbs, although most outgrow it by the age of 5. The habit becomes more serious once children get their permanent teeth, which is usually between the ages of 4 and 6.{relatedarticles}Thumbsucking can contribute to a number of problems including poor tongue placement, speech impediments, overbites, swallowing issues and more. Here are some ways that might help break the habit before it becomes too serious. Stop pressuring your child to quit - this only makes him do it more. Open communication with your child to find out why he is sucking his thumb - are there insecurity issues that need to be addressed?