COLORADO SPRINGS, Colo. -

Teens' perception of marijuana will need to be watched closely, now that it's legal in Colorado, according to one expert.

Recreational marijuana became legal in Colorado Wednesday, but only for adults 21 and older. Still, some parents worry about what that means for their children.

"They may end up believing, except for what they know at home, that it is an acceptable substance," parent Jennifer White said.

Jon Cleckler, a licensed practicing clinician and licensed addictions counselor, said his concern is younger teens, preteens and more impulsive teens.

"It might have the effect of having them feel like it's easier to use, easier to access and it might be OK to use, which is a false perception," he said. "Marijuana affects teenagers differently than it affects adults. Teenage brains and childrens' brains are in a period of development."

Cleckler's advice is to use the change in the law as an opportunity to talk to kids about pot use.

"A parent's job is to have real information, is to have a real good discussion with their teenager about use, about what it does, about what we know about it and about the risks," he said.

He also suggests telling them about the personal and legal consequences of using marijuana. He said parents can use this time to hear what the teens have to say.

"They can get the perceptions of their teenager, the teenager will tell them about their friends and what their friends are saying," he said.

Here is a link to a guide about speaking to kids about drug use.