Infant Crying, Colic, and Gastrointestinal Discomfort in Early Childhood: A Review of the Evidence and Most Plausible Mechanisms

y the time their child is 4 months old, up to 20% of parentshave reported colicky symptoms in their infants. Is infantcolic a disorder? Is it related to the intestine, as the term colicimplies? Is any treatment other than reassurance of families regard-ing the transient nature of these symptoms indicated? In short, arewe stepping in an evidence-based arena or are we dealing with ‘‘gutfeelings’’? This supplement on infant crying, colic, and gastrointestinal(GI) disturbances in early childhood provides theoretical andclinical observations on this and other intriguing functional GItopics. The supplement provides the scientific and clinical evidencethat should guide current clinical practice and serve future studiesthat will enable better understanding and appropriate managementby physicians and families alike.Burns and Thapar review the embryonic and postnatal eventsrelated to the enteric nervous system (ENS), which is the regulatorof gut secretion, blood flow, sensation, and coordinated motility (1). They provide evidence that a significant amount of modification ofthe ENS occurs not only during the fetal period but also postnatally;thus the ENS can be altered in a number of ways: stress, infections,and changes in nutrition.Indrio et al focus on the non-nutritive pathophysiology ofcolic, looking at the relation of colic to gastroesophageal reflux(GER), GI motility disorders, the role of gut hormones, andintestinal microflora (2). Their review raises the old debate ofwhether colic is a functional disorder (eg, troubling GER or‘‘immature’’ motility) or should be regarded as a normal develop-mental occurrence. The authors correctly conclude that ‘‘littleevidence supports a substantial role of GER or GERD in themajority of infants with colic,’’ and observations for the role ofhormones such as ghrelin and motilin as well as the positive effectshown for probiotic supplementation should be studied further.Indrio and colleagues also elaborate on the role of probioticsin the management of infant colic and provide recent and excitingdata on the clinical benefit of the administration of probiotics intreating functional disorders and organic diseases (3). This reviewexplores the hypothesis that there is a window of time when the gutmicrobiota may affect the structure and the function of the brain.The review by Di Lorenzo on early life events brings uselegantly to the ‘‘vulnerable child,’’ summarizing what is knownabout factors that predispose an infant to become colicky (4). Muchof the available data refers to the possible link among infectious,inflammatory, and psychological noxious events that may causechanges in enteric nerve reactivity, as well as immune responses oralterations in intestinal microbiota composition that can then lead tofunctional GI disorders later in life. For example, there is evidencethat early pain experiences are associated with altered painresponses later in infancy. Although the genetic background cannotbe changed and the stressful events may be unavoidable, identifyingthe child at risk may provide an opportunity for interventions thatwill attenuate or prevent later functional disorders.Ha-Vinh Leuchter et al discuss the possibility that the peakshape of the crying behavior found in colicky as opposed to non-colicky babies, the circadian rhythm of the crying, and the obser-vation that these babies are not soothed by ordinary sensorystimulation reflect a difference in central nervous system function-ing (eg, differences in circadian rhythm maturation, differentresponse to stimuli) rather than GI dysfunction (5). Heine summarizes available data on the relation betweencow’s-milk allergy and infant colic (6). He notes that in breast-fedinfants, elimination of cow’s milk and other food proteins from thematernal diet was associated with a greater reduction in crying orfussiness duration, and that the treatment of formula-fed infantswith extensively hydrolysed formula was associated with reducedcrying in several clinical trials. The use of lactose-free formulaeprovides inconsistent results, however. A limited trial of an