Prevalence and correlations of infant gastrointestinal symptoms in the first 6 months of life. Prevalence of flatulence (a), stomach cramps (b), and crying hours (c) of infants from 2 weeks to 6 months (n = 40); >1h/d: infants who cried more than 1 h/d; <1h/d: infants who cried less than 1 h/d. (d) Spearman pairwise correlation map of infant gastrointestinal symptoms during the first 3 months of life (n = 150). The color gradient denotes Spearman R value. Colic criteria 1: paroxysms of irritability, fussing, or crying that start and stop without obvious cause; Colic criteria 2: episodes lasting 3 or more hours per day and occurring at least 3 days per week for at least 1 week; Colic: infants diagnosed by Rome III criteria (see Methods).