The number of states that have legalized recreational use of cannabis more than doubled in the last five years. A new study finds that between 2017 and 2021, the number of very young children eating edible forms of marijuana spiked dramatically, with many kids ending up in hospitals.

The study, released Tuesday in the journal Pediatrics, found that in 2017, there were just over 200 reported cases of accidental consumption of cannabis edibles by children under six. In 2021, the number shot up to 3,054 – an increase of 1,375%.

In total, there were 7,043 exposures to edible marijuana reported to poison control from 2017 to 2021 in children under six.

The vast majority of the kids found the drug in their own home. While most children suffered mild impacts, 22.7% of exposed children needed hospitalization, and 8% of them – 573 children over the five years of the study – needed critical care.

Marit Tweet, an emergency medicine doctor at SIU Medicine in Springfield, Illinois, is the lead author on the study. Tweet's curiosity on the topic piqued in 2019, when she started a fellowship at the Illinois Poison Control Center.

"The big buzz at that time was that cannabis was going to be legalized for recreational, adult use January 1st, 2020" in Illinois, she said. State marijuana laws have been changing rapidly in the past decade, and the drug is legal for medical use in 37 states and for recreational use in 21 states and Washington, D.C.

Tweet was curious how recreational use had gone in other places, so she looked at studies from other states that had already legalized the drug. One study in Colorado documented that the number of children 10 years and under accidentally exposed to marijuana products rose between 2009 and 2015.

So Tweet wanted to know if this would also happen nationally, as more states legalized the drug. She was most concerned about kids 5-years-old and younger, a particularly vulnerable age for accidental poisoning.

"This age group accounts for about 40% of all calls to poison centers nationally," says Tweet. "They can get into things, and you can't really rationalize with them" about dangers.

Marijuana edibles are made to look like sweets, she adds: "They think it looks like candy, and maybe, they just want to eat it."

Tweet and her colleagues analyzed information from the National Poison Data System, which draws on calls to the 55 regional poison control centers that serve the United States and its territories.

Andrew Monte, an emergency medicine doctor at University of Colorado hospital, urges parents who suspect their child ate an edible to take the child to a doctor right away.

"There are some patients that actually have airway obstruction and need to be in the ICU or put on a ventilator," says Monte, who was not involved in the study.

Monte says he and his colleagues see these cases in their emergency department several times a month. Colorado was the first state to legalize marijuana for recreational use in 2012.

Dr. Nora Volkow, who directs the National Institute on Drug Abuse, says the study's findings are concerning.

"It's not just the issue that there are more poisonings of children consuming cannabis, but those consumptions appear to be more serious," says Volkow.

The study should also draw attention to how marijuana edibles are packaged and marketed, Volkow says.

"If you've ever been curious, go to a dispensary or a store where they sell cannabis products, which of course, me being a curious person, I've done," Volkow says. "And the edibles are extremely appealing, in terms of packaging."

She says parents and caregivers who consume edible cannabis products should store them in child-proof containers and keep them out of the reach of children.