As the realities of legalized marijuana take hold in four states and the District of Columbia, legislators and regulators could learn a lot from the successes (and failures) of the tobacco and alcohol industries in keeping their harmful products out of the hands of children and adolescents.

Though well-funded government anti-smoking campaigns insist tobacco companies are marketing to children, there is almost no concern yet about the much looser regulations on marijuana. But changes will have to be made. Voters in Colorado, Washington, Oregon, Arizona and D.C. have already passed laws legalizing recreational marijuana and a number of other states are actively debating proposals to decriminalize recreational marijuana. When marijuana use is legalized for adults - all of the current laws make it legal only for people over the age of 21 - it normalizes the behavior and can put the drugs more easily into the hands of young people. And young people already have readier access to it than they do cigarettes, since cigarette sales are easy to track and would mean heavy fines and possible jail time for selling to children. 

"The early days of marijuana legalization present a unique window of opportunity to create a regulatory environment that minimizes youth access," says Brendan Saloner, PhD, an assistant professor in the Department of Health Policy and Management at the Bloomberg Schooland senior author of a commentary in Pediatrics. "States should heed lessons learned from tobacco and alcohol regulations, which have proven very difficult to change despite research linking weak monitoring and low prices to underage use. Our number one priority has to be to keep our children safe." 

He and co-authors Colleen Barry, PhD, MPP, and Beth McGinty, PhD, MS, suggest four strategies to prevent marijuana use among minors. 

First, they say, regulators should use tax policy to keep prices high. "Research has shown that young people are particularly price sensitive and tend to reduce cigarette use at higher rates than adults after price increases," says McGinty, also an assistant professor in the Department of Health Policy and Management at the Bloomberg School.

Second, retail availability of marijuana should be tightly regulated, they say. Despite age-limit restrictions, many teens are able to obtain alcohol and tobacco in stores. This could be mitigated by stronger enforcement of existing laws, including more compliance audits and stiffer penalties. States should also regulate locations of marijuana retailers, such as keeping them away from playgrounds and schools, which research has shown can reduce risk of youth use. They also suggest prohibiting stores that sell other products from selling marijuana.

Third, they say, efforts need to be made to prevent the harms of accidental ingestion by children, by regulating the appearance of foods containing marijuana and reducing the amount of THC (marijuana's main mind-altering ingredient) in these foods. It was found that tobacco products that feature candy or fruit flavors encourage experimentation, regular use and addiction among youth, they say. In June 2014, Washington state banned using cartoons, toys and other pictures that appeal to young children on marijuana-infused food products and Colorado regulates child-safe packaging of marijuana products.

"Regulators need to be especially aware of how appealing marijuana-laced candies and cookies look to children and adolescents," says Barry, an associate professor in the Department of Health Policy and Management at the Bloomberg School.

Also, childproof packaging can prevent accidental ingestion, which has been shown to be effective for prescription drugs. Clear labeling of marijuana products can also enhance the ability of adults to identify harmful products.

Finally, they suggest that marketing of products to youths should be restricted. Exposure to alcohol and tobacco advertising is associated with increases in youth use, studies have shown.

Marijuana creates its own set of issues that go beyond what has occurred with tobacco and alcohol. Kids don't grow tobacco or make alcohol in their own homes but marijuana has been grown that way for decades and it is harder to regulate what is going on in people's backyards.