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Marijuana: Facts Parents Need to Know

What is marijuana? Are there different kinds?

Marijuana is a green, brown, or gray mixture of dried, shredded leaves, stems, seeds, and flowers of the hemp plant (Cannabis sativa). Cannabis is a term that refers to marijuana and other drugs made from the same plant. Strong forms of cannabis include sinsemilla, hashish ("hash" for short), and hash oil. There are many different slang terms for marijuana and, as with other drugs, they change quickly and vary from region to region. But no matter its form or label, all cannabis products contain the psychoactive (mind-altering) chemical delta-9-tetrahydrocannabinol (THC). They also contain more than 400 other chemicals.

How do people use marijuana?

People who use marijuana may roll loose marijuana leaves into a cigarette (called a joint) or smoke it in a pipe or a water pipe, often referred to as a bong. Some people mix marijuana into foods (often called "edibles") or use it to brew a tea. Another method is to slice open a cigar and replace some or all of the tobacco with marijuana, creating what is known as a blunt. To avoid inhaling smoke, more people are vaping—using vaporizers that allow the person to inhale vapor and not smoke. Another popular method on the rise is smoking or vaping THC-rich resins extracted from the marijuana plant, a practice called dabbing. Some popular e-cigarette devices can be used to vape marijuana or extracts.

How many teens use marijuana?

NIDA's annual Monitoring the Future survey reports that among students from 8th, 10th, and 12th grades, marijuana use has remained stable over the past few years. For the three grades combined, about 24 percent of students reported past-year use in 2015. About 7 percent of 8th graders reported current (past-month) use. Among 10th graders, 15 percent reported current use, and current use for 12th graders was 21 percent.1

Researchers have found that the use of marijuana and other drugs usually peaks in the late teens and early twenties, then declines in later years. Therefore, marijuana use among young people remains a natural concern for parents and is the focus of continuing research, particularly regarding its impact on brain development, which continues into a person’s early twenties. Some studies suggest that the effects of heavy use that begins as a teen can be long lasting, even many years after use discontinues.

How does marijuana work?

When people smoke marijuana, they feel its effects almost immediately. THC (marijuana's psychoactive ingredient) rapidly reaches every organ in the body, including the brain, and attaches to specific receptors on nerve cells. Activation of these receptors in the brain affects pleasure, memory, thinking, concentration, movement, coordination, appetite, pain, and sensory and time perception. THC is chemically similar to chemicals that the body produces naturally, called endocannabinoids, and marijuana disrupts the normal function of these chemicals. Because of this system’s wide-ranging influence over many critical functions, it's not surprising that marijuana can have multiple effects—not just on the brain, but on a person’s general health. Some of these effects last only as long as marijuana is in the body while others may build up over time to cause longer-lasting problems, including addiction. The effects of smoked marijuana can last from 1 to 3 hours. If consumed in foods, the effects come on slower and may not last as long. However, because edibles containing marijuana are often unlabeled or poorly labeled, teens can use too much waiting for the "high" and end up in the emergency room with side effects.

About 45 percent of teens have used marijuana before they graduate from high school.1

What are marijuana's short-term effects?

The short-term effects of marijuana can include:

Euphoria (high). THC activates the reward system in a similar way to other drugs of abuse, resulting in the release of the chemical dopamine.

Memory impairment. THC alters how information is processed in the hippocampus and frontal cortex, brain areas involved in memory and concentration.

Negative mental reactions in some. These include anxiety, fear, distrust, or panic, particularly in people new to the drug or those taking it in a strange setting; some may even experience psychosis.

Physical changes. People who use marijuana may have red or bloodshot eyes, increased appetite ("the munchies"), increased heart rate, and sleep issues.

What determines how marijuana affects an individual?

Like any other drug, marijuana’s effects on a person depends on a number of factors, including the person’s previous experience with the drug or other drugs, biology (e.g., genes), gender, how the drug is taken, and the drug’s potency (its strength). 

How important is marijuana potency?

Potency—determined by the amount of THC contained in the marijuana—has received much attention lately because it's been increasing steadily in the past few decades. These findings are based on analyses of marijuana samples seized by law enforcement.

So what does this actually mean? For someone new to the drug, it may mean exposure to higher concentrations of THC, with a greater chance of a negative or unpredictable reaction. In fact, increases in potency may account for the rise in emergency room visits involving marijuana use. For those more experienced with marijuana, it may mean a greater risk for addiction if they are exposing themselves to high doses on a regular basis. However, the full range of consequences linked with marijuana’s higher potency is not well understood. It is unknown how much people who use marijuana adjust for the increase in potency by using less.

Marijuana can be addictive. People who begin using marijuana before age 18 are 4 to 7 times more likely than adults to develop problem use.8

Does using marijuana lead to other drug use?

Long-term studies of high school students' patterns of drug use show that most young people who use other drugs have first tried marijuana, alcohol, or tobacco. For example, young people who have used marijuana are at greater risk of using cocaine than those who have not. We also know from animal studies that rats given repeated doses of THC show heightened behavioral responses and altered brain activation not only when further exposed to THC, but also when exposed to other drugs such as morphine.9 Researchers are now looking at the possibility that exposure to marijuana as a teen may cause changes in the brain that make a person more likely to get addicted to marijuana or other drugs, such as alcohol, opioids, or cocaine.

It is important to point out, however, that research has not fully explained any of these observations, which are complex and likely to involve a combination of biological, social, and psychological factors. In addition, most people who use marijuana do not go on to use "harder" drugs.

Does smoking marijuana cause lung cancer?

Studies have not found an increased risk of lung cancer in marijuana smokers compared with nonsmokers. However, marijuana smoke does irritate the lungs and increases the likelihood of other breathing problems. Repeated exposure to marijuana smoke can lead to daily cough, more frequent chest colds, and a greater risk of lung infections. Moreover, many people who smoke marijuana also smoke cigarettes, which do cause cancer, and quitting tobacco can be harder if the person uses marijuana as well.

Can marijuana produce withdrawal symptoms when someone quits?

Yes. Many people who use the drug long term and then stop have symptoms that are similar to those of nicotine withdrawal—irritability, sleep problems, anxiety, and craving—which may prompt relapse (a return to drug use). Withdrawal symptoms are generally mild and peak a few days after use has stopped. They gradually disappear within about 2 weeks. While these symptoms do not pose an immediate threat to health, they can make it hard for someone to stop using the drug.

How harmful is K2/Spice (or "synthetic marijuana")?

Spice, which is sometimes also called K2, herbal incense, or "fake weed," consists of shredded dried plant material that has been sprayed with chemicals designed to act on the same brain cell receptors as THC, but are often much more powerful and unpredictable. Spice products are labeled "not fit for human consumption," and many are now illegal. But their manufacturers are constantly creating new chemical compounds to sidestep legal restrictions. Their effects, like the ingredients, often vary, but emergency rooms report large numbers of young people appearing with rapid heart rates, vomiting, and negative mental responses including hallucinations after using these substances.

Are there treatments for people addicted to marijuana?

Behavioral therapies are available and are similar to those used for treating other substance addictions. These include motivational enhancement to develop people's own motivation to stay in treatment; cognitive behavioral therapies to teach strategies for avoiding drug use and its triggers and for effectively managing stress; and motivational incentives, which provide vouchers or small cash rewards for staying drug free.

However, there are currently no medications approved by the U.S. Food and Drug Administration (FDA) for treating marijuana addiction, although promising research is under way to find medications to treat withdrawal symptoms and ease craving and other effects of marijuana.

What are other risks related to marijuana that my child should know?

Many parents and teens may not have thought about some of these risks:

  • As with most drugs, marijuana use interferes with judgment, which can lead to risky behaviors. For example, the person may drive under the influence or ride with someone else who is intoxicated and get into a car crash, or engage in risky sexual behavior and contract a sexually transmitted disease.
  • In addition to psychosis, regular marijuana use has been linked with increased risk for several mental problems, including depression, anxiety, suicidal thoughts, and personality disturbances. One of the potential effects is amotivational syndrome—a diminished or lost drive to engage in formerly rewarding activities. Whether this syndrome is a disorder unto itself or is a subtype of depression associated with marijuana use remains controversial. Furthermore, whether marijuana causes these problems or is a response to them is still unknown. More research is needed to confirm and better understand these links.
  • Marijuana use during pregnancy may harm the developing fetus. Research suggests that marijuana use during pregnancy may be linked to subtle neurological changes and, later in childhood, to reduced problem-solving skills, memory, and attention. However, the fact that pregnant women who use marijuana are also more likely to smoke cigarettes or drink alcohol makes it difficult to determine exactly how much of these effects are due to marijuana. In addition, some research suggests that after pregnancy, THC passes into the breast milk of nursing mothers in moderate amounts. Researchers don't yet know how this affects the baby's developing brain.

Is marijuana medicine?

There has been much debate about the possible medical use of marijuana for certain conditions. A growing number of states have legalized marijuana for medical use, but the FDA, which assesses the safety and effectiveness of medications, hasn't approved marijuana as a medicine. There haven't been enough large-scale studies (clinical trials) showing that the benefits of the whole plant outweigh its risks in the patients it's meant to treat. To be approved, medicines need to have well-defined and measurable ingredients that are consistent from one dose (such as a pill or injection) to the next. In addition to THC, the marijuana leaf contains more than 400 other chemical compounds, which may have different effects in the body and which vary from plant to plant. This makes it difficult to consider its use as a medicine even if some of marijuana’s specific ingredients may offer benefits.

However, THC itself is an FDA-approved medication. Two medicines in pill form (dronabinol [synthetic THC] and nabilone [a synthetic chemical similar to THC]) are available to treat nausea during cancer chemotherapy and boost appetite in people with AIDS. Scientists continue to investigate the medicinal properties of THC and other cannabinoids to better evaluate and harness their ability to help patients suffering from a broad range of conditions.

How can I tell if my child has been using marijuana?

Parents should be aware of changes in their child's behavior, such as not brushing hair or teeth, skipping showers, mood changes, and loss of relationships with family members and friends. In addition, changes in grades, skipping classes or missing school, loss of interest in sports or other favorite activities, a change in peer group, changes in eating or sleeping habits, and getting in trouble in school or with the law could all be related to drug use—or may indicate other problems. See the list of specific warning signs for marijuana use below.

If your child is using marijuana, he or she might:

  • seem unusually giggly and/or uncoordinated
  • have very red, bloodshot eyes or use eye drops often
  • have a hard time remembering things that just happened
  • have drugs or drug paraphernalia—drug-related items including pipes and rolling papers—possibly claiming they belong to a friend if confronted
  • have strangely smelling clothes or bedroom
  • use incense and other deodorizers
  • wear clothing or jewelry or have posters that promote drug use
  • have unexplained lack of money or extra cash on hand

This page was last updated June 2016

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NIDA (2016). Marijuana: Facts Parents Need to Know. Retrieved , from https://www.drugabuse.gov/publications/marijuana-facts-parents-need-to-know

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