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What Is It?

Marijuana is a mixture of the dried and shredded leaves, stems, seeds, and flowers of the cannabis sativa plant. The mixture can be green, brown, or gray.

A bunch of leaves seem harmless, right? But think again. Marijuana has a chemical in it called delta-9-tetrahydrocannabinol, better known as THC. A lot of other chemicals are found in marijuana, too—about 400 of them, many of which could affect on your health. But THC is the main psychoactive ingredient. [1] In fact, marijuana’s strength or potency is related to the amount of THC it contains. The THC content of marijuana has been increasing since the 1970s. For the year 2007, estimates from confiscated marijuana indicated about 8 percent THC on average.

What Are the Common Street Names?

There are many slang terms for marijuana that vary from city to city and from neighborhood to neighborhood. Some common names are: “pot,” “grass,” “herb,” “weed,” “Mary Jane,” “reefer,” “skunk,” “boom,” “gangster,” “kif,” “chronic,” and “ganja.” [2]

How Is It Used?

Marijuana is used in many ways. The most common method is smoking loose marijuana rolled into a cigarette called a “joint” or “nail.” Some users brew it as tea or mix it with food. Others smoke “blunts”-cigars hollowed out and filled with the drug. And sometimes marijuana is smoked through a water pipe called a “bong.” [2]

How Many Teens Use Marijuana?

Some people make the excuse that “everybody's doing it” when they start using marijuana. Well, they need to check the facts, because that’s not true. In 2007, 36 percent of 12th-graders had used marijuana within the past year. Visit http://www.drugabuse.gov/DrugPages/Marijuana.html for the latest information.

What Are the Common Effects?

For some people, smoking marijuana makes them feel good. Within minutes of inhaling, a user begins to feel “high,” or filled with pleasant sensations. THC triggers brain cells to release the chemical dopamine. Dopamine creates good feelings—for a short time. [3]

Imagine this: You're in a ball game, playing out in left field. An easy fly ball comes your way, and you’re psyched. When that ball lands in your glove your team will win, and you’ll be a hero. But, you’re a little off. The ball grazes your glove and hits dirt. So much for your dreams of glory.

Such loss of coordination can be caused by smoking marijuana. And that’s just one of its many negative effects. Marijuana affects memory, judgment, and perception. Under the influence of marijuana, you could fail to remember things you just learned, watch your grade point average drop, or crash a car. Some people may suffer sudden feelings of anxiety and have paranoid thoughts—which is more likely to happen when higher doses are used or when it is taken orally. The problem is that it’s difficult to tell what the effects of marijuana will be for any given person at any time, because they vary based on the person, their drug history, how much marijuana is taken, and its potency. Effects can also be unpredictable when other drugs are mixed with marijuana.

Also, since marijuana can affect judgment and decision making, using it can lead to risky sexual behavior, resulting in exposure to sexually transmitted diseases, like HIV, the virus that causes AIDS.

What Are the Short-Term Effects of Marijuana Use?

The short-term effects of marijuana include:

• problems with memory and learning
• distorted perception
• difficulty thinking and solving problems
• impaired coordination
• increased heart rate

THC Impacts Brain Functioning

THC is up to no good in the brain. THC finds brain cells, or neurons, with specific kinds of receptors called cannabinoid receptors, to which it binds. [3]

Certain parts of the brain have high concentrations of cannabinoid receptors. These areas are the hippocampus, the cerebellum, the basal ganglia, and the cerebral cortex. [3] The functions that these brain areas control are the ones most affected by marijuana.

For example, THC interferes with learning and memory—that is because the hippocampus—a part of the brain with a funny name and a big job—plays a critical role in certain types of learning. Disrupting its normal functioning can lead to problems studying, learning new things, and recalling recent events. The difficulty can be a lot more serious than forgetting if you took out the trash this morning, which happens to everyone once in a while.

Do these effects persist? We don’t know for sure in humans, but studies in rats show that exposure to THC for a long period of time can damage neurons in the hippocampus. So, is it really worth the risk? [3]

Smoking Marijuana Can Make Driving Dangerous

The cerebellum is the section of our brain that does most of the work on balance and coordination. When THC affects the cerebellum’s function, it makes scoring a goal in soccer or hitting a home run pretty tough. THC also affects the basal ganglia, another part of the brain that’s involved in movement control.

These THC effects can cause disaster on the highway. Research shows that drivers on marijuana have slow reaction times, impaired judgment, and problems responding to signals and sounds on the road. Studies conducted in a number of localities have found that approximately 4 to 14 percent of drivers who sustained injury or death in traffic accidents tested positive for delta-9-tetrahydrocannabinol (THC), the active ingredient in marijuana.

Marijuana Use Increases Heart Rate

Within a few minutes after inhaling marijuana smoke, an individual's heart begins beating more rapidly, the bronchial passages relax and become enlarged, and blood vessels in the eyes expand, making the eyes look red. The heart rate, normally 70 to 80 beats per minute, may increase by 20 to 50 beats per minute or, in some cases, even double. This effect can be greater if other drugs are taken with marijuana.

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