Abuse of marijuana is at an all-time high among young people. According to the most recent Monitoring the Future Survey from the National Institute on Drug Abuse, 39 percent of college students use marijuana—the highest levels of use among college students in the past three decades. Furthermore, 36 percent of high school seniors use marijuana, similar to past years, and 6 percent report daily use.
Marijuana abuse, also known as marijuana use disorder, results in marijuana dependence, meaning the person experiences withdrawal symptoms when not using the drug. This occurs when the brain adapts to ongoing use of marijuana by reducing production of its own endocannabinoid neurotransmitters. Marijuana abuse progresses to addiction when users cannot stop abusing the drug even though it is interfering with their daily life.
Marijuana side effects include changes in mood, impaired memory, cognitive difficulties (thinking and problem-solving), respiratory problems (coughing, lung infections, etc.), increased heart rate, hallucinations and paranoia, depression and anxiety, and suicidal thoughts in teens. Moreover, decreased IQ can be a long-term impact of abusing marijuana. One study showed that people who started smoking marijuana heavily in their teens and continued to use it lost an average of eight IQ points between the ages of 13 and 38.
Signs of teen marijuana dependence include irritability, moodiness, difficulty sleeping, decreased appetite, cravings, restlessness, and various forms of physical discomfort. Recent research suggests that 30 percent of those who use marijuana may have some degree of marijuana use disorder. Moreover, scientists have found that people who begin using marijuana before the age of 18 are four to seven times more likely to develop a marijuana use disorder than adults.
Sources: Monitoring the Future Survey, National Institute on Drug Abuse