Each year, hundreds of thousands of babies and their concerned families suffer from colic - a condition diagnosed simply by intense bouts of excessive crying that last for hours.

The cause remains unknown, and despite several treatment options on the market, there's very little scientific evidence that any of them can actually provide relief.

Now a team of scientists suggest there is something that can help - a new study provides the most comprehensive evidence yet that a probiotic called Lactobacillus reuteri, which is already sold as relief for babies with colic, is actually an effective treatment.

Previous studies had questioned the effectiveness of the probiotic. But the new finding is based on a review of four seperate clinical trials involving 345 infants with colic in total, and this big picture view indicates that, for breastfed babies at least, L. reuteri can work.

The trials, conducted in Italy, Poland, Canada, and Australia, looked at how effective L. reuteri was at reducing crying in babies with colic.

While they all drew different conclusions about its effectiveness, the new review of the raw data from the trials – called an individual participant data meta-analysis (IPDMA) – suggests the probiotic is effective for babies with colic who are exclusively breastfed.

Compared to babies taking a placebo, exclusively breastfed infants in the study who received the probiotic were twice as likely to reduce their crying by 50 per cent after three weeks of treatment.

As for formula-fed babies, the results aren't so certain – primarily because of a lack of data on formula-fed infants in the study, since only one of the four clinical trials included formula-fed infants in addition to breastfed babies.

"We did find evidence that L. reuteri is effective in breastfed babies with colic," says MCRI paediatrician Valerie Sung, who also led the Australian clinical trial incorporated in the meta-analysis.

"The role of L. reuteri in formula-fed babies with colic cannot be determined due to lack of studies."

Because of that limitation, the researchers are stopping short of considering the probiotic an automatic cure for infant colic – although it's a promising avenue of treatment for families who breastfeed their baby.

"Parents who are worried about their baby's crying should still see a doctor to check that there is no underlying medical cause for their baby's crying," Sung told ScienceAlert.

"If parents are still keen to try something for their baby, then this probiotic is the best option for those who are breastfed. It should be given directly to the baby as five drops a day for three weeks."

While the data we have at present can't tell us anything more about the prospects for using L. reuteri for formula-fed infants, for many parents who breastfeed, any confirmation of a working treatment that may help reduce the frequent, intense bouts of unexplained crying their babies go through will be a huge relief.

Because of the lack of scientific evidence out there, new parents with colicky babies have been left to try out often expensive treatments without guidance, and there's no standard advice from doctors on how to make their babies feel better.

"It's heartbreaking to watch your newborn child struggle to settle," new mother Kim explained in a press release on the study.

"You try everything you can to help them as you can see how unhappy they are. If there was something that could provide relief I would definitely try it."

The findings are reported in Pediatrics.