Marijuana use by 8th, 10th and 12th grade students increased in 2010, with more American teenagers now using marijuana than cigarettes for the second year in a row, according to numbers released today by the National Institute of Drug Abuse and the University of Michigan as part of the annual Monitoring the Future survey. In 2010, 21.4 percent of high school seniors used marijuana in the last 30 days, while 19.2 had used cigarettes. “It’s really no surprise that more American teenagers are using…