Infant colic--a baby's migraine?

All babies cry. Colicky babies cry more. Infant colic, or excessive crying in an otherwise healthy and well-fed infant, affects approximately 5–19% of babies (1). Infant crying peaks at age 5–6 weeks (corrected for gestational age at birth) and generally decreases by age 3–4 months. Colic is an amplified version of this developmental crying pattern (2,3). While the name ‘‘colic’’ implies a gastrointestinal etiology, direct evidence for this localization is lacking. In the historic 1954 paper by Wessel et al., the syndrome was described as ‘‘Paroxysmal fussing in infancy, sometimes called colic’’(4). ‘‘Paroxysmal fussing’’ may be a more apt descriptive term as all that is clear is that the infants are in distress. While definitions of infant colic vary (5), Wessel’s criteria are commonly used and are the criteria used in the International Classification of Headache Disorders, third edition beta (ICHD-III beta) (appendix): crying for at least three hours a day, at least three days a week, for at least three weeks (or one week for modified Wessel’s criteria) (4,6,7). Despite much research, the cause of infant colic remains poorly understood. Often colic is assumed to be related to feeding—something in the milk, the mother’s diet, the formula or intestinal gas. However, several randomized, placebo-controlled trials have not found gastrointestinal-based treatments to be effective (8–10). Moreover, young infants feed every couple of hours around the clock, yet colicky crying tends to happen more in the evening (2,3). It is important that we ultimately determine the cause of infant colic, as inconsolable and excessive crying causes caregiver frustration and is associated with shaken baby syndrome—a form of child abuse with significant neurologic morbidity and mortality (3,11,12). One percent of parents of 1-month-olds admit to having shaken their baby at least once to try to stop crying, and 2.2% have tried shaking, slapping or smothering. By age 6 months, 5.6% have tried one of these dangerous techniques (11). An association between infant colic and migraine has been reported in several retrospective case-control studies (13–15). In a cross-sectional study, mothers with migraine were more than twice as likely to have an infant with colic, pointing to the possible genetic relationship between infant colic and migraine (6). A recent meta-analysis found the odds of migraine were increased if there was a history of infant colic (odds ratio (OR) 5.6 (95% confidence interval (CI) 3.3–9.5)) (16). What the field has been missing—until now—has been a prospective cohort study examining the relationship between infant colic and migraine, as previous studies’ findings could have been explained by recall bias. In the paper by Sillanpaa and Saarinen, published in this edition of Cephalalgia, the authors used the Finnish Family Competence Study—a study that sampled the general population in a region in Finland and enrolled parents expecting their first child in 1986. At 3 months of age, colic status was assessed using a combination of input from parents and an experienced nurse who spoke to the parents about the frequency, severity, and duration of their baby’s crying episodes. When they grew to age 18, the adolescents completed a questionnaire regarding migraine status using ICHD criteria. Of the 1267 babies originally sampled, migraine outcome data were available in 787 (62%). The proportion with a history of colic did not differ in those who were lost to follow-up. The main finding was that having a history of infant colic predicted development of migraine without aura (relative risk (RR) 2.7 (95% CI 1.5–4.7)), but not migraine with aura. While Wessel’s criteria for colic were not used, this is only a modest limitation as crying duration is often estimated by parents in colic studies. The finding of an association between infant colic and migraine without aura, but not migraine with aura, is interesting and speaks to likely differences in underlying genetics. Migraine is a highly inherited disorder in that the majority of migraineurs have a