Recurrent crying and other forms of distress in young children are often attributed to gastrointestinal (GI) disturbance and consequent discomfort and pain (1–3). In particular, a special term, infant colic, has been coined to reflect this explanation of distress in young infants (2,4–6). Historically, this view can be traced back to what is thought to be the first English language paediatric textbook, Thomas Phaire's “Boke of Chyldren” (7), which listed “Colyke and Rumblyng in the Guttes” as a common childhood ailment. More recently, the English paediatrician Illingworth published reviews that referred to “3-month colic” as crying that was probably caused by “a localised obstruction to the passage of gas in the colon” (5) and as “pain that is obviously intestinal in origin” (3). Other writers from diverse cultures have offered a similar view (8–13).
Although this gut pain explanation of prolonged crying in young children has been popular, it is not self-evident that it is correct. For instance, it is possible that a bout of fierce and prolonged crying could give rise to flatulence, rather than the other way around. The primary question to be examined here is whether this view is supported by a convincing body of evidence, and whether child age needs to be taken into account. The impetus for this review stems from progress made in this research area during the last few years and from the emergence of alternate explanations of recurrent distress in the early months of infancy. The second aim is to consider the implications of the evidence as a whole for clinical practice and future research.
This supplement brings together researchers with expertise in GI function and child psychological and behavioural measurement. It does not adhere fully to the requirements for a systematic review, such as those published by the Cochrane Library (14). This reflects the fledgling nature of this research area and dearth of applicable evidence from blinded randomised controlled trials and meta-analyses. Instead, each component article takes the quality of the evidence into account, gives prominence to evidence from studies with adequate controls replicated by separate research groups, and distinguishes between promising and proven findings. The articles address ≥1 of 4 key questions:
1. What is known about the contribution of GI disturbance to infant/child crying, distress and discomfort behaviours?
2. What is known about other causes of these behaviours?
3. Parents, not young children, complain to clinicians about these phenomena. To what extent do parental individual and cultural characteristics influence parents’ complaints?
4. What are the implications of the evidence for recommendations about clinical management and further research?
Other functional GI disorders in the same age group and the role of early life events in predisposing to the development of childhood functional disorders also are discussed.
DEFINITIONAL AND MEASUREMENT ISSUES
The view that crying, distress or discomfort is caused by GI disturbance involves two inferences: that the observed crying or other distress behaviours are the result of pain or discomfort and that the pain or discomfort is caused by GI disturbance. Each of these steps involves the definitional and measurement challenges of measuring infant distress or discomfort and measuring GI disturbance and symptoms.
Measuring Infant Distress or Discomfort
Infant self-report of pain/discomfort is impossible by definition; self-reports of young children are of importance, but are inadequate on their own. Infant pain or discomfort behaviours can be measured objectively (eg, using acoustic analysis of cry vocalizations, systematic observation of facial expression or body movement). Infant distress behaviours also can be measured by trained observers using behaviour logs (diaries) or rating scales, supported by evidence of validity. For instance, standardised pain scales have been developed for this purpose. Physiological measures, such as heart rate, can be used to provide objective support for the behaviour measures.
Measures of child distress also can be obtained from parent-kept behaviour diaries and rating scales. These methods are more subjective, but evidence of reliability and validity can be used to understand and substantiate them.
Clinical studies, in particular, tend to be based on poorly understood parental concerns and complaints. Parental characteristics such as experience and depression, as well as cultural beliefs and norms, may affect these reports. Two sets of clinical criteria, the Wessel “rule of threes” and the Rome III diagnostic criteria, have been developed by researchers to distinguish clinical cases in a uniform way. The rule of threes defines a fussy/colicky infant as “one who, otherwise healthy and well-fed, had paroxysms of irritability, fussing or crying lasting for a total of more than three hours a day and occurring more than three days in any one week” (15). The Rome III Diagnostic Criteria for Infant Colic were developed to identify this type of functional GI disorder in the neonatal/ toddler period (2). These criteria require all of the following: paroxysms of irritability, fussing, or crying that start and stop without obvious cause; episodes lasting ≥3 hours/day and occurring at least 3 days/week for at least 1 week; and absence of failure to thrive. These 2 sets of criteria are similar in focusing on the amount of crying and its sudden and unexplained onset and in requiring evidence of good health. They raise measurement challenges, which are considered in the individual articles in this supplement.
Measuring GI Disturbance and Symptoms
The implication that a child's distress, pain, or discomfort is caused by a GI disturbance can be supported by 5 main types of evidence:
1. Observational studies, which document differences in GI anatomy, function, or symptoms between children with and without distress or discomfort behaviours.
2. Developmental studies, which explain how differences in GI anatomy or function develop.
3. Studies of mechanism or process, which explain how a GI disorder produces discomfort or pain.
4. Treatment studies, particularly those using double-blind randomised controlled trials, which demonstrate that interventions that modify GI function reduce children's distress or discomfort.
5. Effectiveness studies, which establish that interventions that work in controlled conditions generalise to routine health services settings and are acceptable to parents and children. Cost-effectiveness studies can assess treatment value.
No single study can meet all of these requirements, so the purpose of the articles to follow is to evaluate the strength of the evidence and the implications for research and practice, when these methodological conditions are taken into account.
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