The year's Monitoring the Future survey, an annual survey conducted by researchers at the University of Michigan, was carried out in classrooms around the country earlier this year, with almost 46,000 students surveyed.
The 2012 survey shows that 6.5 percent of high school seniors smoke marijuana daily, up from 5.1 percent five years ago. Just over 36 percent said they smoked within the previous year.
Locally, Inv. Reagen Clayton with the Carroll County Sheriff's Office said marijuana use is up as well, partially because of the changing perception of its effects.
"There's this social acceptance that's growing out there," Clayton said. "They categorize marijuana as completely harmless."
The survey's perception question showed that 41.7 percent of eighth graders see use as being harmful. That rate is the lowest since the survey began tracking risk perception for the age group in 1991. As teens get older, their perception of risk diminishes. Only 20.6 percent of high school seniors see occasional use as harmful, the lowest since 1983.
Clayton, who was recently re-elected as chairman of the Carroll Meth Awareness Coalition, said it's ironic that while the public perception of marijuana has gone down, the potential harm of the drug has actually increased.
"It's much more potent and has such a higher concentration of THC than it used to," Clayton said. "And those factors are so easily manipulated. It's getting so potent, and yet it's being belittled at the same time."
An earlier survey this year, funded by the National Institute of Health, showed that people who used cannabis heavily in their teens and continued through adulthood showed a significant drop in IQ between the ages of 13 and 38 — an average of eight points for those who met criteria for cannabis dependence.
This finding is consistent with other studies showing a link between prolonged marijuana use and cognitive or neural impairment that Clayton described.
"There are so many misconceptions out there about the drug," Clayton said. "People think it can't hurt them, but it's still a primary, leading gateway drug. I won't say it's No. 1, but it's up there."
The investigator said there was no "A-B-C" order addicts follow from one drug to another, but marijuana, tobacco and alcohol are the three that most commonly lead to harder drugs.
"They keep searching for that bigger high," Clayton said. "And that's what gets them into trouble. People are just uneducated about it — they don't realize that the marijuana of today is not the same as it used to be. Society turning a blind eye doesn't help."
Use of other illicit drugs among teens continued a steady, modest decline. For example, past year illicit drug use (excluding marijuana) was at its lowest level for all three grades. Among the most promising trends for drug enforcers, in the past year the use of Ecstasy among seniors in high school was at 3.8 percent, down from 5.3 percent last year.
For the first time, the survey this year measured teen use of the much-publicized and emerging family of drugs known as "bath salts," containing an amphetamine-like stimulant that is often sold in drug paraphernalia stores. The data showed a relative low use among 12th graders at 1.3 percent. In addition, the survey measured use of the hallucinogenic herb Salvia, finding the past year's use dropped among 12th graders, down to 4.4 percent from last year's 5.9 percent.
Abuse of synthetic marijuana (also known as K-2 or Spice) stayed stable in 2012 at just over 11 percent for the past year among 12th graders. While many of the ingredients in Spice have been banned by the U.S. Drug Enforcement Agency, manufacturers attempt to evade these legal restrictions by substituting different chemicals in their mixtures.
The results showed a continued steady decline in alcohol use, with reported use at its lowest since the survey began measuring rates. More than 29 percent of eighth graders said they have used alcohol in their lifetime, down from 33.1 percent last year, and significantly lower than the peak rate of 55.8 percent in 1994.
Cigarette smoking continues at its lowest levels among the grades test, with dramatic long-term improvement. Among eighth graders, 15.5 percent reported smoking regularly, down from last year's 18.4 percent. This is compared to nearly 50 percent at its peak in 1996.
Overall, 45,449 students from 395 public and private schools participated in this year's Monitoring the Future survey. Since 1991, the survey has measured drug, alcohol and cigarette use and related attitudes in 8hth, 10th and 12th graders.
As for fixing the problem of rising marijuana use, Clayton said the "curiosity" needs to be taken away.
"They have this curiosity that they want to experience that euphoric high," Clayton said. "They see it portrayed in their favorite movies and TV shows, and they want to reenact it. Unfortunately, that leads to harsher drugs on down the road."