Marijuana is the most common illicit drug used in the U.S., although the federal government classifies it as a Schedule I substance. This means it has no medicinal uses and carries a high risk for abuse.
Studies show that when young people are heavy users, IQ loss often results. Smoking weed also carries the same risk as cigarette smoking: constant coughing, lung irritation, susceptibility to lung infections and cancer [source: National Institute on Drug Abuse ].
However, people have long clamored for the government to allow marijuana to be used for medicinal purposes, citing its help in treating seizures, medication-induced nausea and chronic pain from injuries. But physicians ignored these pleas, insisting the drug was far too dangerous.
Since 1996, some 20 states have passed laws allowing marijuana's use for medicinal purposes, and medical professionals are witnessing its often-positive results. As a result, many physicians are changing their minds about legalization. Dr. Sanjay Gupta and Dr. Mehmet Oz are two prominent physicians who say they now support medical marijuana [source: Baca]. Gupta, for one, said in 2013 that he should have considered some of the "remarkable research" coming from smaller labs in foreign countries, plus the scores of patients testifying to how much medical marijuana helped their symptoms before making his decision. And in a 2014 survey, 56 percent of physicians said medical marijuana should be legalized nationwide [source: Rappold].