Weed use that begins as a teenager can lead to a drop of up to 8 IQ points. The younger you are when you begin smoking weed, the greater your IQ plummets. Memory loss, cognition, and decision-making are also impacted. We all know weed isn't deadly. But the decisions you make as a teenager will follow you into adulthood, and will impact your quality of life.

Here’s how science says that happens:

The main chemical in weed that affects the brain is delta-9-tetrahydrocannabinol (THC). When weed is smoked, THC quickly passes from the lungs into the bloodstream, which carries it to organs throughout the body, including the brain. As it enters the brain, THC attaches to cells, or neurons, with specific kinds of receptors called cannabinoid receptors. Normally, these receptors are activated by chemicals that occur naturally in the body. They are part of a communication network in the brain called the endocannabinoid system. This system is important in normal brain development and function.

The functions that these brain areas control are the ones most affected by weed:

• Learning and memory. Disrupting its normal functioning can lead to problems studying, learning new things, and recalling recent events.
• Coordination. THC affects the cerebellum, the area of our brain that controls balance and coordination. These effects can influence performance in such activities as sports, driving, and video games.
• Judgment. Using weed can cause you to do things you might not do when you are not under the influence of drugs.

Within a few minutes after inhaling, a person’s heart rate speeds up, the bronchial passages (the pipes that let air in and out of your lungs) relax and become enlarged, and blood vessels in the eyes expand, making the eyes look red. While these and other effects seem harmless, they can take a toll on the body.

• Increased heart rate. When someone uses weed, their heart rate—normally 70 to 80 beats per minute—may increase by 20 to 50 beats per minute or, in some cases, even double. The increased heart rate forces the heart to work extra hard to keep up.
• Respiratory (lung and breathing) problems. Smoke from weed irritates the lungs, causing breathing and lung problems among regular users similar to those experienced by people who smoke tobacco—like a daily cough and a greater risk for lung infections such as pneumonia.
• Increased risk for mental health problems. Weed use has been linked with depression and anxiety, as well as suicidal thoughts among adolescents. In addition, research has suggested that in people with a genetic risk for developing schizophrenia, smoking weed during adolescence may increase the risk for developing psychosis and developing it at an earlier age.

The effects of weed on the brain and body can have a serious impact on a person’s life.

• Reduced school performance. Students who smoke weed tend to get lower grades and are more likely to drop out of high school than those who do not use weed. The effects of weed on attention, memory, and learning can last for days or weeks. These effects have a negative impact on learning and motivation. People who use weed regularly for a long time are less satisfied with their lives and have more problems with friends and family compared to people who do not use weed.

Yes, weed is addictive. A user may feel the urge to smoke weed again and again to re-create the “high.” Repeated use could lead to addiction—which means the person has trouble controlling their drug use and often cannot stop even though they want to.

About 1 in 6 teens who use it every day become addicted to weed. What causes one person to become addicted to weed and another not to depends on many factors—including their family history (genetics), the age they start using, whether they also use other drugs, their family and friend relationships, and whether they take part in positive activities like school or sports (environment).

People who use weed may also feel withdrawal when they stop using the drug. Withdrawal symptoms may include:

• Irritability
• Sleeplessness
• Lack of appetite, which can lead to weight loss
• Anxiety
• Drug cravings

These effects can last for several days to a few weeks after drug use is stopped. Relapse (returning to the drug after you’ve quit) is common during this period because people also crave the drug to relieve these symptoms.

No. There is no evidence of overdose deaths from weed use. However, people can and do injure themselves and die because of weed's effects on judgment, perception, and coordination, for example, when driving under the influence of the drug.

If you or a friend are in crisis and need to speak with someone now, please call:

National Suicide Prevention Lifeline at 1-800-273-TALK (they don't just talk about suicide—they cover a lot of issues and will help put you in touch with someone close by).

If you need information on treatment and where you can find it, you can call:

Santa Clara Valley Behavioral Health Department: 408-272-6594