Sucking of the hand, fingers, or thumb has been observed in utero as early as 29 weeks of gestation and is a nearly universal phenomenon in healthy newborns. Hand or digit sucking is usually harmless, but if it persists, can be associated with a number of problematic sequelae.
The most frequent sequelae of persistent digit sucking are social. Children who suck their thumbs are often nagged and reprimanded by their parents and other adults, which may lead to family conflict and/or unhappiness or insecurity in the child. In a 1993 study, Friman showed 1st grade children pictures of their peers who were thumb sucking and pictures of the same peers when they were not thumb sucking. The children rated their peers who were sucking their thumbs as less intelligent, less happy, less attractive, less likable, and less fun, as well as less desirable as a friend or playmate. The next most frequent sequelae of persistent digit sucking are dental problems such as anterior open bite, decreased alveolar bone growth, mucosal trauma, and even altered growth of the facial bones.
Treatment of thumb sucking is rarely indicated in children younger than age 4 years. In older children, if the sucking occurs infrequently (only at night) or is a transient response to a stressor, then treatment is also rarely indicated. Treatment may be indicated if the sucking causes dental problems, digit malformation, tissue damage, distress to the child, or excessive family conflict.
Treatment for hand/digit sucking usually involves some combination of reinforcement for not sucking (e.g., praise, tangible rewards), application of aversive taste to the nail/skin (e.g., Stop-Zit from Purepac Pharmaceutical Co.), or physical barriers to sucking (e.g., gloves, hand socks, thumb splints.) Firman and Leibowitz (1990) combined a reward system with aversive taste treatment and achieved cessation of thumb sucking in 12/22 children within 3 months and 20/22 within one year.
When necessary, intraoral dental appliances can be effective treatments. Such appliances provide a reminder not to suck and interfere with the seal that sucking creates. When a fixed maxillary appliance is placed the clinician may find a desired cessation of a digital habit because the appliance has unbalanced the pattern of satisfaction from sucking.
