A number of recent studies were not able to conclusively find that probiotic drops soothed babies' colic.
The studies were especially inconclusive for babies who were formula fed, MedPage Today reported.
Only half of the 12 randomized trials that were analyzed found babies with colic cried less when treated with probiotics, according to a meta-analysis, MedPage reported.
Three of the five trials that looked at colic management found breastfed babies were more likely to find relief from probiotics than those on a formula diet.
Out of the two other trials included in the analysis, one found formula fed babies with colic would benefit from the probiotic drops, while the final trial found even breastfed babies did not respond to the treatment.
"Larger and more rigorously designed randomized clinical trials are needed to examine the efficacy of the probiotic Lactobacillus reuteri in the management of breastfed and particularly formula-fed infants with colic and in the prevention of colic in healthy term infants," researchers wrote, MedPage reported.
About 20 percent of infants under the age of three months cry for "no apparent reason."
"It has a negative impact on the mother's mental health, overall family quality of life, and "is the most common proximal risk factor for child abuse," the researchers wrote.
A University of British Columbia study found the "crying curve for babies with shaken baby syndrome parallels that of a normal crying curve" but that instances of the abuse-related syndrome tend to peak four to six weeks after the peak of the crying curve.
Another study found babies who cried excessively in infancy after the age of three months were more likely to exhibit "anxiety, hyperactivity, sleep disorders, and allergies" later in life.
"We do not know what causes colic and not all crying is down to colic. The baby may be crying because they are cold or have a dirty nappy," Janet Fyle, of the Royal College of Midwives said, the BBC reported. "All babies are different.
There were other holes in the trials; infants from varied populations were included in the studies, some trials used infant crying diaries (which could be subject to bias), and the mothers in two of the trials were on a dairy-free diet.
Lana Gagin, MD, a pediatric specialist at Helen DeVos Children's Hospital, Spectrum Health, said breastfeeding is the best defense against colic, MedPage reported.
