You may have heard it called pot, weed, grass, ganja, or skunk, but marijuana by any other name is still a drug that affects the brain.
- October 27, 2014
As more communities allow medical marijuana, or decriminalize illicit marijuana, veterinarians are seeing an alarming trend. More and more dogs are arriving in emergency animal hospitals with marijuana toxicosis, or marijuana poisoning.
A recent study in Colorado showed that 4 times as many dogs were treated for marijuana poisoning in 2010 than in 2005. Sadly, two dogs identified in that study died. Similarly, from 2008 to 2013, the Pet Poison Helpline—a poison control hotline for animals—has seen a 200% increase in calls related to pets eating marijuana.
Most times, dogs ingest marijuana accidentally by eating a marijuana “edibles,” such as cookies or brownies, or getting into their owner’s supply. However, there are some instances where people deliberately give marijuana to their dogs or blow marijuana smoke in their faces to “get them high.” Maybe that sounds funny to people that are high, but it is very dangerous for their dog.
While it is rare that a dog will die from marijuana poisoning, serious medical issues such as injury or dehydration can occur. Marijuana can cause dogs to become disoriented and lose coordination, leading to missteps and falls, even to the point they can’t drink water from their bowl. Symptoms of marijuana poisoning in dogs include anxiety, panting, lethargy, impaired balance (staggering or being unable to walk), drooling, vomiting, diarrhea, trembling, or extreme responses to noises, movements, or other stimulus.
So, the next time you see one of those “dogs high on weed” videos on YouTube, give it a thumbs down. And be sure to keep your furry friends away from marijuana. Even if you believe in free choice when it comes to marijuana, you can agree that animals aren’t being given a choice when marijuana is carelessly left out for them to eat or when owners expose them for kicks. Even unintentional exposure from secondhand smoke can be harmful.
While the debate continues about the usefulness of medical marijuana, some veterinarian groups are looking at using compounds found in the marijuana plant for animals. However, those compounds would be carefully tested and monitored by medical professionals and have no relationship to careless exposure to helpless pets.
Tell us in comments: What would you do if you knew someone was exposing their dog or other pets to marijuana?
- November 03, 2014
Not many people would say with a straight face that drugs like heroin or methamphetamine are good for you, let alone they could help you be more successful in life. But there are lots of people who think marijuana is different from other drugs. For example, we’ve already talked in this blog about the idea that it may have medical uses. The jury is still out.
Some users even say marijuana’s mind-altering effect—the “high”—is also beneficial. They claim using the drug chills them out, expands their mind, and makes them more creative. Since the 1960s, marijuana has had a mystique as an aid to the artistic life.
What does science say?
Many studies over the years have found that marijuana indeed makes users perceive themselves as having more creative thoughts and ideas—which would help explain why so many artists and musicians tout its benefits.
But perception isn’t always the same as reality—and we know that marijuana alters perceptions. In fact, the research on cannabis and creativity suggests that even if users feel more creative, it’s actually an illusion. People may even be less creative after using it.
For example, a new study of almost 60 cannabis users in The Netherlands looked at the effects of the drug on a measure of creativity called divergent thinking—which means the ability to brainstorm, think flexibly, and come up with original solutions to problems. After inhaling a high or low dose of vaporized cannabis or a vapor with the same odor and taste but no THC (the chemical that causes the high), the participants took a test that asked them to come up with as many creative uses for two common items (like a pen or a shoe) as they could.
The results surprised even the researchers: Low doses of cannabis did not have any effect on the participants’ ability to think creatively, compared to not taking cannabis. And high doses actually lowered their creativity—by a lot.
It seems that feeling creative and being creative really aren’t the same thing.
Yet it is also true that your expectations about a drug do matter. Different studies have shown that people who are unknowingly given a placebo instead of a drug (or alcohol) will act or perform in ways that correspond to how they expect the drug to affect them.
Marijuana on Your Mind
One study, for example, found that regular marijuana users who ate biscuits containing marijuana were less creative than a control group who didn’t eat any biscuits, and that both of those groups were less creative than a group who ate biscuits they thought contained marijuana but were actually a placebo.
It goes to show that your mind, including your beliefs about drugs, have a lot more power than you think. You don’t have to take the drug to get the effect you expect—in fact it works best if you don’t!
What do you think? Do you know people who take marijuana (or other drugs) to help them be more creative? Do you think it helps or hurts them? Let us know in comments.
- November 10, 2014
Question: If you look at the candy in the check-out aisle in your local store, an average chocolate bar is 1 serving, and an average bag of candy-covered chocolates (which has about 30 candies) is also 1 serving.
What is the average serving of a marijuana edible chocolate bar or bag of a candy that has been infused with THC—the active ingredient in marijuana?
Answer: There is no average serving.
Yes, it was a trick question. But that’s kind of what marijuana edibles are…tricky. At least for a person who doesn’t use marijuana regularly.
For example, in Colorado, a single serving of an edible marijuana food product purchased for adult recreational use (as opposed to medicinal use) can’t have more than 10 milligrams of THC in it. BUT, there can be up to ten servings in the product or package. That means a single bag of marijuana candy, a marijuana chocolate bar, a marijuana brownie, or any other marijuana edible might contain as much as 100 milligrams of THC.
Smoking marijuana delivers to the user about 5 mg of THC in one puff. So if you ate all ten gummies in a bag of marijuana candy—each one a single 10 mg “serving”—it would be like taking 20 hits of a marijuana cigarette at one time! Because it takes longer to feel the effects of the THC when you eat an edible compared to smoking marijuana—up to an hour or two, this happens a lot. People end up eating more than the recommended serving because they don’t “feel” it right away.
But really, it also goes against how most people eat candy. When was the last time you just had one candy from a bag?
Beverages containing cannabis can be even more confusing. For example, one product contains 7.5 servings in a bottle that is about the same size as a can of soda. Does that mean that you are supposed to take only one sip? A sip and a half?
Manufacturers may say it’s a great drink to share, but do you really want to share a bottle with 7.5 friends? That’s a little too much sharing, if you ask us. (And how do you find half a friend?)
We all know that these THC-infused edibles and drinks are illegal for teens to use and buy. But many will find ways to try them. They may find, however, that it isn’t worth long nights coping with overwhelming dizziness, hallucinations, and stomach sickness (common symptoms of overdose)—and for a growing number of unlucky experimenters, trips to the emergency room.
That’s what happened to New York Times reporter Trish Reske’s 21-year-old son, who had to be rushed to the hospital after eating all 6 servings of a marijuana chocolate bar. Not a great way to spend an evening.
Tell us in comments: What should manufacturers do to make marijuana edibles safer?Tags:Marijuana
- November 17, 2014
Do you know how long it took for tobacco smoking rates to significantly drop after researchers first linked smoking cigarettes to cancer? 40 years.
In the 1920s, when the link to cancer was discovered, smoking was normal---in fact, ads for cigarettes even featured doctors saying it relieved stress! For years, people smoked in their homes and offices, in restaurants and stores, on planes and on trains. Wherever they went…they smoked. In 1957, the nation’s top doctor—the U.S. Surgeon General—warned that cigarette smoking could cause lung cancer. Other government doctors began to speak out. Still, people continued to smoke.
Overtime, laws to protect the public’s health limiting where people could smoke, increases in the cost of cigarettes, and the growing body of evidence that smoking was directly linked to lung cancer helped lead turn the tide. Now, it’s surprising to find people smoking inside—it’s the norm for people to have to go outside.
Today, it is marijuana that people, especially younger people, are beginning to view as ‘okay’ or ‘less dangerous’ or ‘normal.’ It reminds us of tobacco nearly 100 years ago—and not in a good way.
A big difference, though, is for teens —we already know that using marijuana comes with some serious risks. Evidence is strong that smoking marijuana on a regular basis can harm the developing teen brain. And long-term, regular use of marijuana starting in the teen years can impair brain development and lower IQ. In other words, the brain may not reach its full potential.
As more and more states legalize marijuana for adults, it will likely be easier to get (even for teens), and there’s a chance that the number of people who use it will increase. For teens, this could have real and lasting effects. The question is, how long will it take before perception catches up to reality?
Scholastics shares the facts surrounding the great marijuana debate with its recent article, ‘Marijuana: Breaking Down the Buzz’.
Tell us in comments, is marijuana the next tobacco? Do these facts change your perception?
For additional facts about the brain and drugs, visit scholastic.com/headsup.
- November 24, 2014
In concerts, at house parties, even in the hallway of apartment buildings, you may have come into contact and been exposed to secondhand marijuana smoke.
In situations like these, people often worry how breathing someone else’s marijuana smoke affects them. A couple of common questions and the answers may help you see through the fog of this smoky situation.
Can you get high from inhaling secondhand marijuana smoke?
You may have heard the phrase “contact high,” about someone breathing secondhand marijuana smoke and feeling a buzz. There have been studies that show in extreme conditions, with lots of smoke blown directly into your face, you can feel the high and it can even show up in a urine test. But this is not a normal circumstance.
Studies show that very little THC is exhaled back into the air when a smoker exhales. So little, in fact, that if you sat in a room while people exhaled the smoke of four marijuana cigarettes (sometimes called joints) in one hour, you wouldn’t get high. You would have to be trapped in a room breathing the smoke of 16 burning joints before it you started to show signs of being high.
Can you fail a drug test from inhaling secondhand marijuana smoke?
Again, probably not.
Since the amount of THC exhaled by marijuana smokers is so low, it would take a lot of secondhand exposure to fail a drug test.
In a 2010 study, researchers measured the effect of secondhand marijuana smoke on non-marijuana smokers. The non-smokers were placed in a well-ventilated space with people casually smoking marijuana for 3 hours. The researchers then took blood and urine samples from the nonsmokers. They found that THC was present, but the amount was well below the level to needed to fail a drug test. Another study found similar results: Testing positive is rare and limited to the hours directly following exposure.
What are the health effects of inhaling secondhand marijuana smoke?
Researchers are still working to figure this out. We still don’t know how a person is affected if they live with a regular marijuana smoker. We also don’t know how higher amounts of THC in today’s marijuana cigarettes affects secondhand smoke.
A recent study on rats suggests that secondhand marijuana smoke can do as much damage to your heart and blood vessels as secondhand tobacco smoke. But that study has not yet been done on humans.
We also know marijuana smoke contains harmful and cancer-causing chemicals, the same way tobacco smoke does. But we still don’t know how it affects a person’s health in the long run. Lots more research still needs to be done.
Tell us in comments, what would you do if someone was smoking marijuana near you?
- September 08, 2014
This is the first post of a 3-part series on the science of medical marijuana. Check out Part 2: Making Medicine From Marijuana, and Part 3: Medicines or Poisons?—Why Cannabinoids Can Both Help and Hurt You.
Before modern medical science, most medicines were raw herbs or herbal concoctions of one sort or another. They sometimes helped patients, but those benefits weren’t very powerful by today’s standards, and they often had a lot of unpredictable or even dangerous side effects. That’s because all plants contain hundreds or thousands of different chemicals. If you eat or smoke the leaves of any plant, you are putting all those chemicals in your body, and the results can be unpredictable.
Marijuana is no different.
Still, there is growing public support for “medical marijuana,” based on anecdotal evidence (that is, from individual people’s personal experience) that the drug might be useful in treating various diseases, including PTSD (post-traumatic stress disorder), pain, and epilepsy.
Voters in 23 states have now passed laws allowing marijuana to be dispensed to patients, as long as they receive permission from a doctor.
Why Doesn’t the Food and Drug Administration (FDA) Approve “Medical Marijuana”?
Turns out, there’s very little scientific evidence that smoking or eating marijuana is effective and safe for treating any medical issues. Scientific evidence would have to come from carefully controlled research studies.
Since there’s no science to back it up, the FDA has not approved smoked or vaporized marijuana for the treatment of any medical condition.
The FDA only approves medicines when large studies examining lots of patients (called clinical trials) show that the medicines work safely. Without these studies, the FDA can’t promise people that the medications will help them and not harm them.
So why haven’t there been clinical trials on marijuana?
Because marijuana is a raw herb. There are over 500 different chemicals in marijuana, in combinations that vary widely between different strains and even from plant to plant. This causes serious problems trying to use the whole marijuana leaf, or crude extracts like hash oil, as medicine:
- It’s hard to deliver precise, accurate doses of the right chemicals;
- It can harm the lungs if users smoke it; and
- It causes additional effects—like the “high”—that may interfere with the quality of life of patients taking the drug for serious medical conditions.
Plus, when used by teens or children, it could even harm their brains as they develop.
Today, there are almost no approved medicines that are whole herbs. Although it’s not impossible, it would be very unusual if marijuana became an exception.
So how can we discover and use marijuana’s medical benefits without the harms?
Stay tuned for Part 2, to learn how scientists are busy trying to create actual medicines from the chemical ingredients in marijuana.
- December 01, 2014Studies show that marijuana interferes with attention, motivation, memory, and learning. Students who use marijuana regularly tend to get lower grades and are more likely to drop out of high school than those who don’t use. Those who use it regularly may be functioning at a reduced intellectual level most or all of the time.Check out NIDA's new infographic that explains what that means in the classroom, and how that can affect your life.[Click here to view larger version of this infographic or the text-only version]Tags:Marijuana
- September 15, 2014
This is the second post of a 3-part series on the science of medical marijuana. Check out Part 1: What’s Wrong With “Medical Marijuana”? and Part 3: Medicines or Poisons?—Why Cannabinoids Can Both Help and Hurt You.
What people usually mean by “medical marijuana” is use of an unprocessed (raw) plant to treat illness—or herbal medicine, in other words. Unprocessed means the leaves, stems, or seeds are just taken off the plant and used.
Before the 20th century, that’s mostly what medicine was.
But science has made a lot of progress in the last several decades, and generally it hasn’t looked back. It’s because we now have ways of picking out the specific chemicals that are useful from plants and putting just those parts in a pill, without all the unwanted chemicals that might cause side effects or even be toxic.
This is what a lot of scientists are busy doing right now with marijuana—trying to figure out which chemicals in the plant really are useful in treating health problems and then finding ways to deliver them safely and effectively to patients to treat their conditions.
Turning Marijuana into Medicine
At the last count, scientists have found over 500 separate chemicals in the marijuana plant. The main chemical that gives users the “high” is tetrahydrocannabinol, or THC, but there are over 100 other chemicals in marijuana that have a similar molecular structure to THC. This family of chemical compounds is called cannabinoids.
So far, there are two FDA-approved medications containing THC for treating nausea and appetite problems caused by cancer chemotherapy and AIDS. Other drugs with THC in them have been approved already in other countries for treating symptoms of multiple sclerosis (MS) and are now being carefully tested before being approved in the United States.
Another marijuana chemical is cannabidiol, or CBD. News reports have highlighted some families who are living in states where medical marijuana is legal so their children with bad forms of epilepsy can get special high-CBD marijuana extracts to help control seizures.
These extracts probably still contain other, possibly harmful ingredients. But a medicine only containing CBD is now being tested in the United States. If the science finds that CBD really is a good treatment for seizures, eventually patients may be able to take that or another safe, CBD-based medication. This could help people get the safe treatment they need.
Cannabinoids and Other Diseases
Lots of different cannabinoid chemicals are being studied to see whether they have beneficial effects on conditions ranging from addictions and other mental health problems to pain and other serious conditions. Most are still a long way from being studied in humans and going on to become medications.
In Part 3, we’ll look at why chemicals in the marijuana plant could be so helpful even though they may also be harmful. It turns out, marijuana’s not unique in being two-faced!
- September 22, 2014
People who write about the health benefits of marijuana sometimes think it’s ironic that a plant containing compounds that could treat disease (like THC or CBD) is banned by the government for being unsafe. But in fact many effective, FDA-approved medicines are closely related to illegal, harmful drugs and are sometimes even made from the same sources.
That’s because there’s a fine (and sometimes fuzzy) line between chemicals that are good for you and those that can hurt or even kill you. In fact, the Greek word pharmakon, where we get pharmacy, originally meant both “medicine” and “poison.”
Speaking the Body’s Language
The opium poppy is a great example. It’s the source of a drug called morphine, part of a class of drugs called opioids. Morphine is used to make heroin—a very addictive and sometimes deadly drug. But it is also modified and used to make many effective, relatively safe pain relievers prescribed widely by doctors and dentists. In fact, these opioids are our most valuable drugs for pain relief.
Another example is cocaine, from the coca plant. It is part of a class of drugs called stimulants. Cocaine is an especially dangerous, addictive stimulant, but it is closely related to medications used to treat people with attention deficit hyperactivity disorder (ADHD) and other conditions. It is also used sometimes as an anesthetic.
The thing that makes a drug a drug is the ability to speak the body’s language—specifically, to interact with one of the many chemical signaling systems that cells use to talk to each other. Both heroin and cocaine are able to do that, fluently.
Same with marijuana: Its cannabinoid chemicals speak the body’s own endocannabinoid language.
Nerve cells use chemicals called neurotransmitters to send each other messages, and there are several different kinds of neurotransmitters. Similar chemicals in plants or in foods can interact with these neurotransmitter systems because their molecules are very similar to the ones produced naturally in the human body.
Morphine from the poppy plant is able to work in your nervous system because it closely resembles your body’s own natural pain-relieving opioid chemicals—the endorphins that cause a “runner’s high.” (The “endo” in endorphin or endocannabinoid means “from inside”—that is, inside your body.)
Cocaine and related stimulants work with your own neurotransmitter dopamine, which naturally keeps you focused on rewarding activities.
And the THC in marijuana interacts with the endocannabinoid signaling system used by the body’s own cannabinoid chemicals—such as anandamide—in brain circuits that control a wide range of things including pleasure, memory, thinking, concentration, movement, coordination, and even how you perceive time. That’s why THC is able to interfere with these abilities when people smoke marijuana either to get high or to treat a medical condition.
The endocannabinoid system also is involved in things like appetite and pain, which is why THC has been made into an effective medication for helping treat nausea and loss of appetite in AIDS and cancer-chemotherapy patients. And it is why it may, in the future, be prescribed for treating pain as well.
So, there’s nothing special about marijuana: It’s one of many plants that contain substances that can be both beneficial and harmful, depending on how they are used.
- October 06, 2014
Marijuana has long been seen as an “alternative” drug. It was illegal for everyone, and those who used it regularly were seen as “stoners” or “hippies” or “partiers” and were somehow different than “regular” people. There was a stereotype of people who used marijuana and most people didn’t think much about it.
And then came the rise of medical marijuana, and that began to change marijuana’s reputation. It was seen, by some, as medicine, and in some states people were able to get a prescription for it and use it to help them with specific health problems. Marijuana started to change its image. Now, along with the typical marijuana user, there were people who had medical conditions enabling them to get a prescription and use marijuana legally.
But the biggest change in marijuana’s image is what has happened in two states, Colorado and Washington, where marijuana has been made legal for adults to use, with or without a prescription. This change pushed marijuana out of the shadows and into the spotlight.
Marijuana is still not as popular as alcohol or tobacco in those states, but this new identity as a “legal drug” has come with a change in perception that marijuana is safe, and that the reasons it was illegal before no longer exist.
This really worries people who dedicate their lives to the health of the public. That’s especially true when it comes to people who care about teens, whose brains are actively developing and may really be damaged by marijuana use.
Colorado is working to counter the effects of marijuana’s image makeover by constructing human-sized rat cages to raise awareness about the effects of marijuana on young people, getting the point across that using it as a teenager is kind of like doing an experiment on your brain. Thus the campaign’s message: “Don’t be a lab rat” and questions like “Can marijuana really cause schizophrenia in teenagers? Volunteers, anyone?” The cages are displayed in places popular with kids and teens, such as a skate park and the public library.
Tell us in comments: Do you think advertising campaigns can help teens see that marijuana is still dangerous for them to use?
- October 20, 2014
You already know the dangers of using marijuana before driving: Marijuana seriously impairs your motor skills and clouds your perception and judgment, all of which you need to safely operate a car. That’s why it’s illegal to drive high. But lots of people don’t know this … or they know it, but figure it’s okay “just this one time.” Whatever the case, it’s breaking the law, just like driving after drinking alcohol.
Driving under the influence of marijuana is a big problem. A 2007 study by the National Highway Transportation Safety Administration found that 8.7 percent of people driving at night on a weekend had been using marijuana—4 times the percentage of drivers who had had enough alcohol to impair them.
With all of these drugged drivers, police need an easy test to check if people have been using marijuana, like they have for alcohol. Unfortunately, there isn’t one—yet.
A Marijuana Breathalyzer
With alcohol, police can test a driver’s breath and tell if the person has enough in their system to impair their driving—a device called a breathalyzer. This works because alcohol leaves the body quickly. This also means that the breathalyzer only measures alcohol that has been recently used.
Measuring marijuana, however, turns out to be way, way more complicated.
For one thing, marijuana can stick around in a person’s body a lot longer than alcohol. It can be detected in blood tests of heavy users as much as a month after they’ve stopped using it! So in theory, heavy marijuana users could test positive in a blood test for marijuana even if they haven’t used it in a few weeks.
Another tricky thing with marijuana is that, after taking it, frequent users may show a higher amount of THC (marijuana’s active ingredient) in their body fluids than infrequent users do, even if the effect on their driving abilities is similar.
This means there’s a big need for a test that can universally tell when a person has consumed marijuana during the previous few hours, when it can have its biggest impact on driving ability—whether or not he or she uses the drug frequently or just occasionally. It also needs to be easy to use by police and painless for drivers.
Scientists are hard at work on the problem, and last fall a team of researchers at NIDA’s Intramural Research Program had a breakthrough: a first successful test of a marijuana breathalyzer.
Getting High for Science
In their research study, the scientists had a group of frequent marijuana-using adults and a comparison group of occasional marijuana-using adults each smoke a single marijuana cigarette (with an exactly measured dose of THC) and then provide breath samples using a device called SensAbues. Both groups tested positive up to an hour later, and frequent users tested positive 2 hours later.
So far it’s not perfect, and even though the collection device is very portable, the equipment to test the results isn’t, so there are still some hurdles. But it’s one step closer to making the roads safer from drugged drivers.
Tell us what you think in comments: Do you think if the police had a marijuana breath test, it would deter people from using marijuana before driving?
Check out these PSAs from Colorado reminding residents that while recreational use of marijuana is legal—driving under the influence of marijuana is illegal.
Also known as: “weed,” “pot,” “bud,” “grass,” “herb,” “Mary Jane,” “MJ,” “reefer,” “skunk,” “boom,” “gangster,” “kif,” “chronic,” and “ganja”
Marijuana is a mixture of the dried and shredded leaves, stems, seeds, and flowers of Cannabis sativa—the hemp plant. The mixture can be green, brown, or gray. Stronger forms of the drug include sinsemilla (sin-seh-me-yah), hashish (“hash” for short), and hash oil.
Of the approximately 400 chemicals in marijuana, delta-9-tetrahydrocannabinol, known as THC, is responsible for many of the drug’s psychotropic (mind-altering) effects. It’s this chemical that changes how the brain works, distorting how the mind perceives the world.
It is illegal to buy, sell, or carry marijuana under Federal law. The Federal Government considers marijuana a Schedule I substance—having no medicinal uses and high risk for abuse. However, across the United States, marijuana state laws for adult use are changing. As of 2014, 23 states and the District of Columbia have passed laws allowing the use of marijuana as a treatment for certain medical conditions.
In addition, four states and the District of Columbia have legalized marijuana for adult recreational use. Because of concerns over the possible harm to the developing teen brain and the risk of driving under the influence, marijuana use by people under age 21 is prohibited in all states.
Strength and Potency
The amount of THC in marijuana has increased over the past few decades—from an average of about 4 percent for marijuana and 7.5 percent for sinsemilla in the early 1990’s to almost 10 percent for marijuana and 16 percent for sinsemilla in 2013.1 Scientists don’t yet know what this increase in potency means for a person’s health. It could be that users take in higher amounts of THC, or they may adjust how they consume marijuana (like smoke or eat less) to compensate for the greater potency.
The honey-like resin from the marijuana plant has 3 to 5 times more THC than the plant itself. Smoking it (also called “dabbing”) can potentially lead to dangerous levels of intoxication requiring emergency treatment. People have been burned in fires and explosions caused by attempts to extract hash oil using butane (lighter fluid).
Marijuana is commonly smoked using pipes, water pipes called “bongs,” or hand-rolled cigarettes called “joints” or “nails.” It is sometimes also combined with tobacco in partially hollowed-out cigars, known as “blunts.” Recently vaporizers, that use heat without burning to produce a vapor, have increased in popularity. Marijuana can also be brewed as tea or mixed with food, sometimes called edibles.
In addition, concentrated resins containing high doses of marijuana’s active ingredients, including honey-like “hash oil,” waxy “budder,” and hard amber-like “shatter,” are increasingly popular among both recreational and medical users.
The main chemical in marijuana that affects the brain is delta-9-tetrahydrocannabinol (THC). When marijuana 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.
Most of the cannabinoid receptors are found in parts of the brain that influence pleasure, memory, thinking, concentration, sensory and time perception, and coordinated movement. Marijuana triggers an increase in the activity of the endocannabinoid system, which causes the release of dopamine in the brain's reward centers, creating the pleasurable feelings or “high.” Other effects include changes in perceptions and mood, lack of coordination, difficulty with thinking and problem solving, and disrupted learning and memory.
Certain parts of the brain have a lot of cannabinoid receptors. These areas are the hippocampus, the cerebellum, the basal ganglia, and the cerebral cortex. (Learn more about these areas and how THC affects them.) The functions that these brain areas control are the ones most affected by marijuana:
- Learning and memory. The hippocampus 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. A recent study followed people from age 13 to 38 and found that those who used marijuana a lot in their teens had up to an 8 point drop in IQ, even if they quit in adulthood.3,4
- Coordination. THC affects the cerebellum, the area of our brain that controls balance and coordination, and the basal ganglia, another part of the brain that helps control movement. These effects can influence performance in such activities as sports, driving, and video games.
- Judgment. Since THC affects areas of the frontal cortex involved in decision making, using it can cause you to do things you might not do when you are not under the influence of drugs—such as engaging in risky sexual behavior, which can lead to sexually transmitted diseases (STDs) like HIV, the virus that causes AIDS—or getting in a car with someone who’s been drinking or is high on marijuana.
When marijuana is smoked, its effects begin almost immediately and can last from 1 to 3 hours. Decision making, concentration, and memory can suffer for days after use, especially in regular users.2
If marijuana is consumed in foods or beverages, the effects of THC appear later—usually in 30 minutes to 1 hour—but can last over 4 hours.
Learn more about how the brain works and what happens when a person uses drugs.
Yes, marijuana is addictive. A user may feel the urge to smoke marijuana 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.
It is estimated that about 1 in 6 people who start using as a teen, and 25% to 50% percent of those who use it every day, become addicted to marijuana. What causes one person to become addicted to marijuana 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 marijuana may also feel withdrawal when they stop using the drug. Withdrawal symptoms may include:
- Lack of appetite, which can lead to weight loss
- 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.
The changes that take place in the brain when a person uses marijuana can cause serious health problems and affect a person’s daily life.
Effects on Health
Within a few minutes after inhaling marijuana smoke, 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 marijuana, 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. The increased heart rate forces the heart to work extra hard to keep up.
- Respiratory (lung and breathing) problems. Smoke from marijuana 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. While research has not found a strong association between marijuana and lung cancer, many people who smoke marijuana also smoke cigarettes, which do cause cancer. And, some studies have suggested that smoking marijuana could make it harder to quit cigarette smoking.5
- Increased risk for mental health problems. Marijuana 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 marijuana during adolescence may increase the risk for developing psychosis and developing it at an earlier age. Researchers are still learning exactly what the relationship is between these mental health problems and marijuana use.
- Increased risk of problems for an unborn baby. Pregnant women who use marijuana may risk changing the developing brain of the unborn baby. These changes could contribute to problems with attention, memory, and problem solving.
Effects on School and Social Life
The effects of marijuana on the brain and body can have a serious impact on a person’s life.
- Reduced school performance. Students who smoke marijuana tend to get lower grades and are more likely to drop out of high school than their peers who do not use. The effects of marijuana on attention, memory, and learning can last for days or weeks. These effects have a negative impact on learning and motivation. In fact, people who use marijuana 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 marijuana.
- Impaired driving. It is unsafe to drive while under the influence of marijuana. Marijuana affects a number of skills required for safe driving—alertness, concentration, coordination, and reaction time—so it’s not safe to drive high or to ride with someone who’s been smoking. Marijuana makes it hard to judge distances and react to signals and sounds on the road. Marijuana is the most common illegal drug involved in auto fatalities. High school seniors who smoke marijuana are 2 times more likely to receive a traffic ticket and 65% more likely to get into an accident than those who don’t smoke.6 In 2011, among 12th graders, 12.5% reported that within the past 2 weeks they had driven after using marijuana.7 And combining marijuana with drinking even a small amount of alcohol greatly increases driving danger, more than either drug alone. Learn more about what happens when you mix marijuana and driving.
- Potential gateway to other drugs. Most young people who use marijuana do not go on to use other drugs. However, those who use marijuana, alcohol, or tobacco during their teen years are more likely to use other illegal drugs. It isn’t clear why some people do go on to try other drugs, but researchers have a few theories. The human brain continues to develop into the early 20s. Exposure to addictive substances, including marijuana, may cause changes to the developing brain that make other drugs more appealing. Animal research supports this possibility—for example, early exposure to marijuana makes opioid drugs (like Vicodin or heroin) more pleasurable. In addition, someone who uses marijuana is more likely to be in contact with people who use and sell other drugs, increasing the risk for being encouraged or tempted to try them. Finally, people at high risk for using drugs may use marijuana first because it is easy to get (like cigarettes and alcohol).
For more information on the effects of marijuana, see our Marijuana Research Report.
6. U.S. Department of Transportation. National Highway Traffic Safety Administration. Traffic Safety Facts. Drug Involvement of Fatally Injured Drivers. Washington, DC, November 2010. Available at: http://www-nrd.nhtsa.dot.gov/Pubs/811415.pdf.
It is very unlikely for a person to overdose and die from marijuana use. However, people can and do injure themselves and die because of marijuana's effects on judgment, perception, and coordination, for example, when driving under the influence of the drug. Also, people can experience extreme anxiety (panic attacks) or psychotic reactions (where they lose touch with reality and may become paranoid).
Marijuana is the most common illicit drug used in the United States by teens as well as adults. The growing belief by young people that marijuana is a safe drug may be the result of recent public discussions about medical marijuana and the public debate over the drug’s legal status. In addition, some teens believe marijuana cannot be harmful because it is “natural.” But not all natural plants are good for you—take tobacco, for example.
See the most recent statistics on teen drug use from NIDA’s Monitoring the Future study below:
Swipe left or right to scroll.
Monitoring the Future Study: Trends in Prevalence of Marijuana/ Hashish for 8th Graders, 10th Graders, and 12th Graders; 2014 (in percent)* Drug Time Period 8th Graders 10th Graders 12th Graders Marijuana/ Hashish Lifetime 15.60 33.70 44.40 Past Year 11.70 [27.30] 35.10 Past Month 6.50 16.60 21.20 Daily 1.00 [3.40] 5.80
For more statistics on teen drug use, see NIDA’s Monitoring the Future study.
There is no difference between marijuana dispensed to treat a medical condition and marijuana bought on the street for recreational use. The difference is just in how it is used.
The marijuana plant contains chemicals that may be useful for treating a range of illnesses or symptoms. A growing number of states (23 as of August 2014) have legalized the plant’s use for certain medical conditions. Although it is not legal or considered medicine by the Federal Government a few medications made from active chemicals in the plant called cannabinoids have been approved by the U.S. Food and Drug Administration (FDA). One of these cannabinoids, THC, has some medicinal properties in addition to its mind-altering effects. Pill versions of THC have been approved to treat nausea (feeling sick) in cancer patients and to increase appetite in some patients with AIDS.
Another cannabinoid chemical called cannabidiol, which doesn’t have mind-altering effects, is also being studied for its possible uses as medicine. A new medication with a combination of THC and cannabidiol is available in several countries outside the United States as a mouth spray for treating symptoms of multiple sclerosis. There is some early evidence that cannabidiol may be useful in treating seizures in children with severe epilepsy, so a cannabidiol-based drug for that is also now being studied.
It is important to remember that because marijuana is often smoked, it can hurt lung health; these health risks as well as the way it impairs mental functioning may outweigh its value as a medical treatment, especially for people that are not very sick with cancer or other life-threatening diseases. Another problem with smoking or eating marijuana plant material is the ingredients vary a lot from plant to plant, so there is no way to get a precise dose every time or even know what dose you are getting. This is why scientists are busy studying safe ways that THC, cannabidiol, and other chemicals can be extracted from the marijuana plant to create safe medicines.
For more information, see Drug Facts—Is Marijuana Medicine?
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:
- Substance Abuse Treatment Facility Locator at 1-800-662-HELP or visit www.findtreatment.samhsa.gov.
For more information on how to help a friend or loved one, visit our Have a Drug Problem, Need Help? page.
- Commonly Abused Drugs Chart
- DrugFacts: Marijuana
- Marijuana: Facts for Teens
- Marijuana: Facts Parents Need to Know
- Mind Over Matter Teaching Guide and Series: Marijuana
- NIDA Notes Articles: Marijuana
- Research Report Series: Marijuana
Statistics and Trends
Monitoring the Future (University of Michigan):
Substance Abuse and Mental Health Services Administration: