Cigarettes are a natural nemesis for parents of teenagers. But perhaps parents should be more worried about marijuana.

A recent annual report by the National Institute on Drug Abuse at the University of Michigan says pot smoking went up for 2010 over the previous year in all three grades surveyed: eighth, 10th and 12th.

And then there's this: More high school seniors smoked marijuana (21.4 percent) during the last 30 days than smoked cigarettes (19.2 percent).

The institute says marijuana affects learning, judgment and motor skills at a time when young brains are still developing and are most at risk.

Worse yet, about one in six people who start using marijuana as adolescents tend to become addicted.

A team of social scientists at the institute conducts the research with the help of research grants from one of the National Institutes of Health.

Massive survey

More than 46,000 students in eighth, 10th and 12th grades from 396 public and private schools around the country participated in the study.

But marijuana use isn't the only cause for concern:

- Significant increases in the use of the drug Ecstasy, apparently because of a recent decline in the belief that the drug is dangerous.

- Non-medical use of prescription drugs - such as Vicodin and OxyContin - remains high.

The study does have some bright spots.

For instance, binge drinking continues to decline. Among high school seniors, 23.2 percent reported having five or more drinks in a row over the last two weeks.

Less binge drinking

That's down from 25.2 percent in 2009 and far from the high mark of 31.5 percent in 1998. The use of flavored alcoholic drinks among the age groups is also down.

The big challenge is to reverse the attitudes about the harm and effects of illicit drug use, particularly marijuana.

The public debate over medical marijuana and its value for adults might be affecting youth concerns about the use of marijuana, researchers suggested.

Regardless, parents, churches, youth groups - along with federal, state and local officials - need to do all they can to alert teens about the seriousness of drug abuse along with its dangers.

The points can't be overstressed.

If studies have shown anything, it's that the anti-drug message must be reinforced constantly. The groups of youths who need to hear it are ever changing while the threats never end.