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The reported occurrence rates of infantile colic vary from 10% to 40%. 1-4 Many reviews only use data from selected populations. 3-8 Differences may reflect differences in definitions, methods of data gathering, and study design.
In epidemiological and more clinically oriented studies, infantile colic has been defined in different ways but prolonged crying is an almost constant feature. However, studies define normal and prolonged crying differently. The most commonly accepted is the "rule of 3": crying during at least three hours per day on at least three days of at least three weeks. The first two features originated from a description by Wessel and colleagues. 9 The third is often not established because of problems in documenting the condition. Other time criteria that have been used are: severe crying for several hours per day, 10 crying for more than two hours per day, 11 and overall duration of more than three hours per day. 12 Studies not using an indication of crying time define infantile colic as unexplained crying, 13 crying seen as a problem, 14 or crying with which parents felt they could no longer cope and for which they sought help. 15 Other sources of variability are the presence of symptoms possibly of gastrointestinal origin (a high pitched pain cry, 1 flatulence, and difficulties with the passage of stools 16 ) and the emphasis on consolability. 1 Apart from these differences, studies generally agree that infants with colic are healthy, thriving, and below 6 months of age. The foregoing could be congruent with two underlying concepts. Firstly, infantile colic is conceived as one distinct entity with prolonged crying as the main symptom and several optional additional features. Secondly, infantile colic is conceived as a collection of different entities, each defined separately.
Different methods have been used to establish the diagnosis, including audiotape recordings, 17 parental diaries, 18 the Crying Patterns Questionnaire (CPQ), 19 non-specified questionnaires, and interviews, personal or by telephone. Crying has been classified in various ways, such as amount of crying in hours per day or answers to a broad question on whether the baby cried a lot. Moreover, some studies assessed crying prospectively with an inception early in life, whereas others used a retrospective data gathering method, sometimes up to...