Harvard brain biologist Bertha Madras has described marijuana as the most dangerous drug in the United States, not only because of its impacts on health, but because what people think they know about it is wrong. Marijuana seems ubiquitous in our society today. So, what should we know?

Americans have radically changed their habits on recreational drugs. Today, 22 percent of Americans currently use marijuana, 20 percent regularly drink alcohol, and 11 percent use tobacco, according to a Marist Poll on “Weed and the American Family.”