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Marijuana legalization is becoming more and more common—so far, 32 states and Washington DC allow the medical use of marijuana, 13 states have decriminalized (though not fully legalized) it, and a further 10 states and Washington DC have legalized it for recreational use for adults age 21 and up.

It might seem like the legalization of marijuana implies that it’s safe, but we know from a large body of research that it can have negative effects on teens’ developing brains. “The major difference between teens and adults has to do with brain development,” says Dr. Stacy Gruber, director of Marijuana Investigations for Neuroscientific Discovery at McLean Hospital and associate professor of psychiatry at Harvard Medical School in Massachusetts. “In our teen years, we are not fully developed from a neurological perspective and that’s important,” she says.

Using marijuana before your brain is fully developed (which doesn’t happen until your mid-20s) can have harmful effects on your brain that can last your entire life (especially if you use it regularly, Dr. Gruber says). According to the CDC, regular marijuana use at a young age could lead to problems with memory, learning, and problem solving.

Experts are still debating the pros and cons of legalizing marijuana for adults, but for teens, Dr. Gruber advises paying attention to the risks. “Keep in mind, you just get the one brain—make sure you’re doing things to take care of it and protect it.”

Here’s what the experts have to say about both sides of the marijuana legalization debate.

Taxation and racial discrimination

Proponents of legalizing marijuana for recreational use (at age 21 and up) often cite the potential for a big economic boost—if marijuana were legal, it could be regulated and taxed, says Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws (NORML). Between January 2014, when marijuana was first legalized in Colorado, and July 2017, the state made half a billion dollars in cannabis-related revenue.

Legalizing marijuana could also help reduce racial discrimination in the criminal justice system. A 2013 report by the American Civil Liberties Union found that “on average, a black person is 3.73 times more likely to be arrested for marijuana possession than a white person, even though blacks and whites use marijuana at similar rates.”

Other issues surrounding legalizing marijuana are more hotly debated.

smoke in car

The issue: Drugged driving

The case against legalization

“Marijuana use impairs a person’s reaction time, their ability to stay in their lane, and their judgement of distance,” says Dr. Kevin Sabet, president of anti-marijuana advocacy group Smart Approaches to Marijuana (SAM). “Legalization is making our roads—already dangerous due to substances currently legal—even more dangerous.”

The case for legalization

Driving under the influence, whether that’s of marijuana or another substance like alcohol, is already illegal, says Armentano. “Laws legalizing and regulating the adult use of cannabis in private do not change this fact.” In other words, driving under the influence of any substance is extremely dangerous and should always be avoided—there’s no debate about that.

What the research says

A 2018 report by the Insurance Institute for Highway Safety found that car accidents had increased by six percent in four states that had legalized marijuana for recreational use. More research is needed to determine whether marijuana legalization has to do with this increase.

The issue: Problems for students

The case against legalization

A 2014 study published in Lancet found that teens who smoke pot daily are more than 60 percent less likely to finish high school. The study also found significant relationships between marijuana use and suicide attempts, addiction, and other illegal drug use.

The case for legalization

Legalizing marijuana might make it easier to address some of these issues, says Armentano. Regulating the sale of marijuana means governments could regulate the process by which it’s produced and sold safely to adults, he says, better restricting sales to minors at the same time. That, “coupled with a legal environment that fosters open, honest dialogue between parents and children about cannabis’s potential harms, best reduces the risks,” he says.

Remember: Even in states where it’s legal, you have to be 21 to use marijuana. Before you make any decisions about marijuana, it’s important to seriously consider the potential risks (just like you would with alcohol).

The issue: Other drug use

The case against legalization

Some research suggests marijuana use might specifically be linked to the opioid crisis. Cannabis use is associated with an increased risk of “nonmedical prescription opioid use,” according to a 2018 study published in the American Journal of Psychiatry. “At a time when our country is literally in the midst of an addiction epidemic, the last thing we need to be doing is normalizing the use of another addictive substance,” Dr. Sabet says.

The case for legalization

Cannabis isn’t harmless, Armentano acknowledges. “We as a society shouldn’t turn a blind eye to problematic use,” he says, adding that the best strategy is to regulate marijuana’s use and educate people about the risks.


The possible health effects of regular marijuana use are still being researched and debated. Some risks have been fairly well documented, including:

Cough and chest infections

Regular marijuana smoking is associated with coughing and phlegm, bronchitis, and an increased likelihood of having respiratory infections.

Heart and lung problems in some users

Marijuana use initially increases a person’s heart rate and blood pressure. In most healthy users, the cardiovascular effects are not associated with serious health problems. However, marijuana use is riskier for people with preexisting heart conditions.

Mental health issues

Marijuana use has been linked to several mental health issues and even psychiatric disorders, according to the National Institute on Drug Abuse. Studies have linked cannabis to depression, anxiety, and even schizophrenia—the latter of which can be made worse by smoking pot.

Read more about how marijuana can affect your health here.

Potential health benefits

Researchers’ interest in marijuana goes far beyond using it for pain relief. Marijuana interacts with human cells in diverse ways, offering the potential for a range of medical uses. Scientists are interested in the potential effects of marijuana on glaucoma (an eye condition that can cause blindness), some cancers, autoimmune disease, inflammation, pain, seizures, gastrointestinal disorders, drug addiction, anxiety, and post-traumatic stress disorder, among other health conditions. In fact, last year, the Food and Drug Administration (FDA) made history by approving the first drug derived from cannabidiol (CBD), a chemical component in marijuana, to treat certain forms of epilepsy.

Beware the hype

Pressure to legalize medical marijuana has resulted in advocates exaggerating the health benefits. Marijuana has medical potential, but it is not a miracle drug. “A more balanced, science-based approach is desperately needed,” says the Society for Science-Based Medicine, which critically evaluates medical treatments and claims.

And remember, just because marijuana can be used for medical reasons doesn’t mean all use is safe. “Recreational use and medical use of cannabis is very different,” Dr. Gruber says. “Just like we shouldn’t take other people’s medicine, cannabis has different effects in different people.”

Researchers studying how marijuana affects people’s health, behavior, and development have to wrestle with a lot of complicating factors. These factors can lead to mixed results and cause them to question how accurate and relevant these research findings are. They include:

The effects of the drug are variable

The effects of marijuana depend on how the drug is used, how much is used and how often, who’s using it, and in what circumstances.

It’s hard to know what’s causing what

It can be difficult to filter out the effects of marijuana use from the effects of other substances (e.g., other drugs and alcohol), mental and emotional health issues, and other factors.

Study participants may not be typical users

Studies may rely too heavily on users who are seeking treatment or whose struggles may be worse than average. This can introduce bias.

Older studies may be losing relevance

Most research has involved marijuana of lower potency than is generally used today, so the findings might underestimate the effects.

Political agendas

The intense politics around marijuana legalization increase the likelihood that evidence will be misinterpreted, misrepresented, and biased.

Researchers’ limited access to the drug

Legal restrictions limit scientists’ access to marijuana. This is a barrier to conducting research studies on marijuana-based medications and other studies.

Why students support or oppose legalization

In Student Health 101 surveys, students have ranked their concerns or hopes relating to marijuana legalization. Many students with opposing views were able to find common ground. Here’s what they said:

Students’ top reasons for supporting legalization:

  1. Medical treatments for disease and pain
  2. Treating drug use as a health issue rather than a criminal issue
  3. Regulating marijuana more safely

Students’ top reasons for opposing legalization:

  1. Risks of driving under the influence
  2. The risks of dependency and addiction
  3. The risk of sending a message to kids and teens that marijuana is safe
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Article sources

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Kevin Sabet, PhD, president, Smart Approaches to Marijuana (SAM), Alexandria, Virginia.

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