Marijuana has a chemical in it called tetrahydrocannabinol, better known as THC. A lot of other chemicals are found in marijuana, too—about 400 of them, some of which are carcinogenic.42
Pot affects a user’s judgment, motor coordination, and short-term memory. Weed can cause increased heart rate and make some users extremely anxious or paranoid. Smoking marijuana also causes some changes in the brain similar to those caused by long-term use of cocaine and heroin.43
Research found that students with an average grade of “D” or below were more than four times as likely to have used marijuana in the past year as students who reported an average grade of “A.”44 Students who have smoked marijuana within the past year are more than twice as likely to have cut class than those who did not smoke, while health problems associated with using marijuana can keep students from attending school due to illness.45
Regular marijuana users often have shortened attention spans, decreased energy and ambition, poor judgment, high distractibility, and impaired ability to communicate and relate to others. Young people who use marijuana weekly have double the risk of depression later in life.46
Find out more about the myths about smoking weed.