Colic

Although most babies identified as colic cases probably have nothing wrong with them, organic disorders, including food intolerances, can give rise to crying in occasional cases. The best evidence-based estimate is that organic diseases as a whole are responsible for no more than 10 percent of cases where unexplained crying in one- to three-month-old infants is the presenting complaint (Gormally 2001).

There is growing evidence that intolerance of certain foods, especially cow's milk protein, can cause crying in some young babies. The mechanism is not certain, but it appears to be possible for the proteins to be passed via breast-feeding as well as bottle-fed milk or formula. However, reviews by a research pediatrician (Gormally 2001) and pediatric gastroenterologist (Treem 2001) have both concluded that food intolerance of this sort is rare. William Treem estimates that about 2 percent of infants overall are allergic to cow's milk protein, while only 1 in 10 infants taken to clinicians with problem crying have food intolerance. Only around 5 percent of infants diagnosed as having colic have gastroesophageal reflux (gastric acid refluxed into the esophagus). Treem also emphasizes that infants with feed-intolerance or gastrointestinal disorders can often be easily identified, by symptoms such as vomiting and diarrhea, blood in their stools, or a strong family history of atopy, asthma, or eczema.

A second possible cause of colic sometimes proposed is inadequate parenting. As noted above, it remains possible that Western approaches to baby-care as a whole may contribute to infant crying, although there is insufficient evidence to establish if this is the case. In principle, too, parental neglect can cause a baby to cry. However, recent evidence has made clear that many—probably most—Western babies who cry a lot do so in spite of highly sensitive and responsive parental care. Indeed, their parents have usually made extraordinary efforts to resolve the crying. The implication is that there is something about these babies that makes them cry despite care that does not cause crying in most babies.

The search for what this might be has focused on the so-called neurobehavioral shift believed to occur at around two months of age, whereby control over behavior moves from subcortical brain systems to the cerebral cortex. Evidence of this shift can be seen in the disappearance of newborn infant reflexes, such as the grasping reflex, and in the emergence of social smiling and more sophisticated perceptual and cognitive abilities. During this transition period, neurological regulation of behavior is believed to be poor, leading infants to be more or less overreactive, or poor at damping-down their crying once they have started (that is, at self-soothing). Several studies have found evidence that infants who cry a lot are highly reactive when undressed and challenged by handling and standard tests (e.g., White et al. 2000). The goal now is to understand the neurological and developmental processes involved, so that the reasons for the differences in reactivity between babies becomes clear. By understanding the types of stimulation which most provoke reactive behavior, it may also be possible to assist parents in how to minimize it.