Colic in infants is common, occurring in about 1 out of 10 babies. First-born infants seem to be affected with colic more often than later children. It usually begins within 10 days to 3 weeks after birth, and lasts until 3 to 4 months of age, at which time it generally disappears on its own.

In spite of apparent abdominal pain, colicky infants eat well and gain weight normally. The crying episodes may tend to occur around the same time each day, but a few infants will cry almost constantly.

The specific causes of infant colic are not known, but the following factors may play a role:

• air swallowed during the process of crying, feeding or sucking on hands or fingers
• overfeeding with large amounts of formula or breast milk
• family tension and parental anxiety
• intestinal allergies to cow's milk
• esophageal reflux

Recent research suggests that colic may be related to refluxesophagitis, which is a condition that occurs when the esophagus becomes irritated by acid backed up from the stomach into the esophagus. A clue to this would be an infant who arches backward during crying spells, and spells that typically occur within an hour of the last feed.

Other studies suggest that colic has nothing to do with stomach pain after all, but instead reflects the baby's inability to console itself when dealing with all the stimuli present in its new world. It is thought that such babies lag behind a few weeks developmentally. These studies also concluded that this has no bearing on the baby's intelligence or future development and is just as irrelevant to a baby's future as whether he or she starts walking a few weeks earlier or later than others.