Marijuana is the most commonly used illegal substance in the U.S. and its use is growing. Marijuana use among all adult age groups, both sexes, and pregnant women is going up. At the same time, the perception of how harmful marijuana use can be is declining. Increasingly, young people today do not consider marijuana use a risky behavior. But there are real risks for people who use marijuana, especially youth and young adults, and women who are pregnant or nursing. Today’s marijuana is stronger than ever before. People can and do become addicted to marijuana.