This story is part of a partnership between MedPage Today and VICE News.

Teens and adolescents increasingly believe it isn't risky to smoke marijuana occasionally, according to new data from the Substance Abuse and Mental Health Services Administration (SAMHSA).

About 77 percent of teens and adolescents — defined as kids between the ages of 12 and 17 — told surveyors that they perceived "no great risk" from smoking pot once a month, according to the Behavioral Health Barometer, which examines trends in substance use and mental health.

This figure has been steadily increasing since 2010, when 70.4 percent of adolescents said they didn't find using marijuana once a month to be especially risky. In 2002, only 32.4 percent of kids said there was a "great risk" to smoking pot once a month.

"As more states go toward having medical marijuana and having legalized marijuana, that creates a public perception — including among our impressionable youth — that it's safe," Dr. Richard Rosenthal, of Mount Sinai Hospital, who wasn't involved in the report, told VICE News.

"It's actually probably not that dangerous if you think about it pharmacologically in folks that are adults over 25, but among youth, it actually is hazardous," Rosenthal said. "They don't know that it can affect brain development."

Since the brain doesn't finish developing until individuals are in their mid-20s, Rosenthal said using cannabis before then is associated with increased risk of other substance abuse and mental disorders, such as depression.

"I would hazard a guess most youths don't know that," he said.

Using data from the National Survey on Drug Use and Health (NSDUH), SAMHSA researchers found that 7.4 percent of kids ages 12 to 17 said they smoked marijuana in the month prior to being surveyed in 2014 — a 6.7 percent increase since 2008. The figure peaked in 2011 at 7.9 percent, but decreased to 7.2 percent in 2012 and 7.1 percent 2013.

Overall, 9.4 percent of youths — about 2.3 million in total — used some kind of illicit drug in the month prior to being surveyed in 2014.

"As you can see, the numbers are pretty high," said Dr. Peter Martin, director of the Vanderbilt Addiction Center, who also wasn't involved in the study. "I think there's almost a surreal effect in that you look at them and you see how high they are."

Marijuana is still the most commonly used illicit drug among adolescents and teens, but 2.6 percent of survey participants reported using psychotherapeutics, 0.6 percent used inhalants, 0.2 percent used cocaine, and 0.1 percent said they had used heroin.

'Among youth, it actually is hazardous. They don't know that it can affect brain development.'

About 6 percent of adolescents and teens reported binge drinking in the month before the survey, steadily decreasing from 8.9 percent in 2008. Cigarette smoking has decreased as well, with 4.9 percent of surveyed adolescents and teens saying they'd smoked in the month before the survey.

The recent use of pain relievers fell to 4 percent among males and 5.4 percent among females, down from 5.5 percent and 7 percent, respectively.

"There's a nice, general — slow but general — decline," Rosenthal said, attributing the trend to kids starting to understand the dangers of abusing prescription painkillers, a message that the CDC and others have been stressing for years. "That's starting to sink in," he said.

He said the decline may also be the result of combined efforts by state programs, as well as individual doctors and patients, which have taken steps to keep prescription painkillers from getting into the wrong hands.

Other highlights of the report included:

2.8 million adolescents, or 11.4 percent, reported a major depressive episode in the year prior to being surveyed for 2014

Serious thoughts of suicide were highest among 18-to-25-year-olds

Those who were uninsured, below the federal poverty level, and living in non-metropolitan areas were more likely to have serious mental illness than those with insurance, above the poverty level, and in metropolitan areas

Also, of the 9.8 million adults with serious mental illness in the US, only 68.5 percent received treatment or counseling in the year prior to being surveyed. Those who were female and those who were insured were more likely to get treatment.