Experts say the results should change the way parents and pediatricians view colic, considering it not a problem but part of normal infant development.
"Parents should be informed that, in the overwhelming majority of cases colic does remit by 3 months of age, with little if any residual impact," says Tammy J. Clifford, director of epidemiology at the CHEO Research Institute's Chalmers Research Group in Ottawa and lead author of the new study.
Clifford says the findings also rebut earlier theories that maternal anxiety spurs colicky behavior in babies by putting an emotional distance between mother and child. Instead, she says, the stressful crying may temporarily raise a mother's anxiety levels, but by the time babies reach 6 months old that effect has almost always vanished.
Even so, she adds, colic is no laughing matter.
"While it may be a part of normal infant development, it needs to be taken seriously, particularly if families are already at heightened levels of stress," she says. Excessive crying is often cited as the trigger for abuse, such as shaken baby syndrome.
"Parents should not feel guilty about needing to seek some respite from their colicky infant and caregivers, family members and health-care professionals should be aware of the signs of extreme stress and understand the toll it can take," Clifford says.
The researchers report their findings in the December issue of Archives of Pediatrics and Adolescent Medicine.
Colic is the term for prolonged bouts of crying or fussiness, typically three hours or more three days a week. The mysterious condition affects between 5 percent and 28 percent of newborns, with the wide swing attributable to vagaries in the definition of colic, how it was measured in earlier studies, and how those studies were conducted.
Colic has no cure, and its causes are unknown -- contrary to what many parents may think, it's almost never related to abdominal distress. However, some styles of holding and comforting colicky babies may help.
Clifford and her colleagues followed 547 pairs of mothers and infants, including 131 who had colic at 6 weeks of age. Three months later, only 18, or 13.7 percent, still had the condition, although 17 other babies now had crying behavior consistent with colic.
Babies whose colic eased by 3 months were more likely to be girls than boys. Their mothers were more likely to have had anesthesia or painkillers during delivery, to have worked away from home during pregnancy, and to have drank caffeine or alcohol after giving birth.
Clifford's group also followed the mothers to see if levels of anxiety and depression depended on whether their baby had colic. They questioned the women about their emotional health a week after they gave birth, before colic set in, and then again six months later, or roughly three months after it usually ends.
Although women with colicky babies saw their anxiety and depression ebb a little more slowly than the other women, the difference wasn't significant. "Put another way, on the basis of the scores on these anxiety and depression scales, you wouldn't be able to tell which moms had colicky babies and which moms did not," she says.
How fathers react to colicky kids is "an important line of future research," Clifford adds.
Dr. Ronald Barr, a McGill University pediatrician who has studied colic, says doctors and parents need to change the way they think about the condition. Since it's most likely a phase of normal infant development, parents shouldn't feel that if their baby is inconsolable they're doing something wrong, he says.
"You can modify the amount of crying and reduce it some, but you probably can't reduce it altogether no matter what you do," says Barr, author of an editorial accompanying the journal article.
The most important thing parents can do is a don't: When your baby's crying, absolutely do not shake her. Crying is behind 95 percent of childhood injuries caused by shaking, and the vast majority occur during the months when infants cry most, Barr says.
Some parents fear their colicky infants will become troublesome toddlers, but Barr says no evidence backs that concern. In fact, while the issue's not well-researched, what little data exist suggest that babies with early colic may turn out to be better adjusted than those whose crying sprees appear later in their first year. That, in turn, implies that early and late colic have different physical or emotional origins, he adds.
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