MINNEAPOLIS (WCCO) — New numbers reveal more Americans are using marijuana.

The report, released Wednesday, was done by the Substance Abuse and Mental Health Services Administration, and it shows that marijuana use has increased steadily over the past five years.

The nationwide survey found that 7.3 percent of Americans 12 or older regularly used the drug in 2012. That’s compared to 5.8 percent in the year 2007.

The nationwide survey that was just made public involved 70,000 people, ages 12 and older.

It found that about 9.2 percent of the population in the U.S. uses some type of illicit drug, but marijuana is the most commonly used.

WCCO’s Angela Davis talked to a doctor at Hazelden about the increased use of marijuana and what it means for teenagers in particular.

“Research is clear in saying that when people start using at a young age, they are more likely to develop addiction when they are older,” Dr. Joseph Lee said.

Lee has personally seen the effects of addiction to marijuana. He works with young people between the ages of 12 and 25 at Hazelden’s Plymouth campus.

“When young people believe that a certain substance is less dangerous, they are more likely to use it. It seems pretty obvious. But this is what happened with cigarettes, with methamphetamine. This is what happened with prescription drugs,” Lee said.

He described how marijuana affects a teenager’s body and behavior.

“Marijuana does impair memory. It does affect a child’s intellectual development. We know that young people who start using marijuana at a young age, have IQ points much lower than those kids who don’t smoke, later in life,” Lee said.

Lee says that parents need to be aware of the behavior they’re modeling.

“Other parents need to be more careful, cause there may be a history of addiction in their family or a risk of addiction in their young one, so the way they behave and the way they model behavior needs to change accordingly,” he said.

He encourages parents to talk to their kids about marijuana.

“The conversation you have with your kids needs to be simple and very direct. Don’t talk about your wild days; don’t talk about how you used. Don’t give too many examples. Just say when you are young, we don’t expect you to use these substances,” he said.

The survey comes on the heels of last week’s announcement that the Justice Department will not be challenging states that have legalized the use of marijuana, as long as they’ve taken some steps the keep the drug away from minors.

Colorado and Washington have legalized marijuana, and 20 states have approved marijuana for medical use.

Another interesting finding in the study deals with heroin. It found an 80 percent increase in the number of heroin users since 2007.