11 Things to Know About Pot and Your Health

Do marijuana's benefits outweigh its risks? Here's a look at the pros and cons of the drug.

As more states legalize marijuana, it's important to know the pros and cons of pot—and what effect it might have on your health. The US Drug Enforcement Administration (DEA) lists marijuana and its cannabinoids (biologically active components in marijuana) as Schedule I controlled substances, which means it cannot legally be prescribed, possessed, or sold under federal law. Nor is whole or crude marijuana (including marijuana oil or hemp oil) approved by the US Food and Drug Administration (FDA) for any medical use. But the use of marijuana to treat some medical conditions is legal under state laws in many states.

With its increasing use, Health looked at recent research and spoke with several experts to learn about the risks and benefits of marijuana to your health.

It May Help (or Aggravate) Anxiety and PTSD

Cannabis smokers often report that they use the drug to relax or to relieve emotional stress. A 2017 study published in Drug and Alcohol Dependence found that a very low dose of THC (the main psychoactive compound in marijuana that makes people feel "high") helped people feel less nervous about a public-speaking task.

But it may not be that simple: That dose was equivalent to only a few puffs on a marijuana cigarette, said the study authors. They also found that slightly higher amounts of TCH—anything that would produce even a mild high—actually made anxiety worse. The research "indicates cannabinoids could be helpful for people with anxiety," lead author Emma Childs, PhD, associate professor of psychiatry at the University of Illinois at Chicago, told Health. But more research is needed, she said, to determine appropriate dosages and delivery methods, and to prevent the opposite effects from happening.

Quantity and experience of the user matter, says the National Institute on Drug Abuse (NIDA). Pleasant experiences with marijuana, such as relaxation and euphoria, are not experienced by all. Some people experience anxiety, fear, distrust, or panic. This is more common when a person takes too much, the marijuana has an unexpectedly high potency, or the person is inexperienced. People who have taken large doses of marijuana may experience an acute psychosis, which includes hallucinations, delusions, and a loss of the sense of personal identity.

It Can Relieve Chronic Pain and Nausea

Pain relief is a common use for medical marijuana. And the National Academies of Sciences concluded there is indeed good evidence to support this practice. Marijuana products also appear to be effective at calming muscle spasms caused by multiple sclerosis and easing nausea and vomiting due to chemotherapy, the report stated.

The National Academies also determined that there is moderate evidence that cannabis or cannabis-derived products may help people who have trouble sleeping due to sleep apnea, fibromyalgia, or chronic pain.

People With EpilepsyMay Benefit

In a 2018 study published in the New England Journal of Medicine, cannabidiol oil—a derivative of marijuana—reduced seizures by 39% in children with Dravet syndrome, a rare form of epilepsy. That was big news for parents who have been using medical marijuana for years, often illegally, to help their kids suffering from this debilitating condition.

The cannabidiol oil used in the study—approved by the FDA in 2018 and marketed as Epidiolex—won't make people high, because it doesn't contain THC. Experts say that results may be riskier and more unpredictable with other marijuana products.

It May Be a Safer Alternative to Opioids

A 2016 study in the journal Health Affairs found that there were 1,826 fewer daily doses of painkillers prescribed per year, on average, in states where medical marijuana was legal compared to states it was not. And in a review published in Trends in Neuroscience, researchers concluded that cannabinoids may help people recover from opioid addiction. Human trials have been limited because of marijuana's classification as a Schedule 1 drug—but the authors argue that more studies are urgently needed.

Still, cautions the NIDA, some research suggests that marijuana use is a "gateway drug" or a drug that is likely to precede the use of other licit and illicit substances and could lead to the development of addiction to other substances. In animal experiments, THC (the mind-altering chemical in marijuana, responsible for most of the intoxicating effects that people seek) showed an ability to "prime" the brain for enhanced responses to other drugs.

It May Have Anti-cancer Effects, but Research Is Limited

According to the American Cancer Society (ACS), some studies have reported that THC and other cannabinoids such as CBD slow growth and/or cause death in certain types of cancer cells growing in lab dishes. Some animal studies also suggest certain cannabinoids may slow growth and reduce spread of some forms of cancer.

Gregory Gerdeman, PhD, assistant professor of biology at Eckerd College, told Time that there have also been anecdotal patient reports and "increasing numbers of legitimate clinical case studies … that all indicate tumor-fighting activities of cannabinoids." It's still unknown, however, whether traditional forms of marijuana would be an effective cancer therapy, or what cancer types it might actually work against.

Risks to Baby When Pregnant

According to a 2019 JAMA Pediatrics article, more pregnant women are using marijuana. There is some evidence of an association between marijuana use during pregnancy and future developmental and hyperactivity disorders in children, says NIDA. Research shows that pregnant women who use marijuana have a 2.3 times greater risk of stillbirth, as per NIDA. The American College of Obstetricians and Gynecologists (ACOG) recommends that obstetrician-gynecologists counsel women against using marijuana while trying to get pregnant, during pregnancy, and while they are breastfeeding, based on the potential of marijuana to negatively impact the developing brain of the fetus. ACOG also states that there's no evidence that marijuana helps morning sickness.

Current parents should also use marijuana with caution. A 2019 study published in Prevention Science found that people tend to cut back on marijuana use once they have kids, but they don't always quit. That's concerning, said lead author and research scientist Marina Epstein, PhD, because parental marijuana use is strongly related to children's use—and children's use is associated with higher rates of health problems.

"Children watch what their parents do," Epstein told Health. "I would encourage parents to be talking to their kids and be clear about expectations for their kids about using or not using marijuana and the amount, especially with their teenagers."

Risk of Heart Attack

According to NIDA, there is evidence that a person's risk of heart attack during the first hour after smoking marijuana is nearly five times his or her usual risk. This increased risk could be because marijuana raises blood pressure (in some cases) and heart rate and reduces the blood's capacity to carry oxygen.

In 2014, a study published in Forensic Science International reported two cases of sudden death that doctors linked to health complications possibly worsened by marijuana use. The authors wrote, "To our knowledge, these are the first cases of fatal cannabis smoking where full postmortem investigations were carried out."

And in 2017, a review published in Nature Reviews Cardiology noted that there had been a tenfold increase in the THC content of marijuana over the previous ten years as well as an increase in widespread availability of highly potent synthetic cannabinoids for recreational use. The authors concluded these factors have led to an increase in the number of severe cardiovascular incidents reported, including myocardial infarction, cardiomyopathy, arrhythmias, stroke, and cardiac arrest.

It's Not Safe To Use Marijuana and Drive

According to NIDA, marijuana can impair judgment, motor coordination, and reaction time. Studies have found a direct relationship between blood THC concentration and impaired driving ability.

In addition, as per NIDA, marijuana is the illicit drug most frequently found in the blood of drivers who have been involved in vehicle crashes, including fatal ones. A 2012 meta-analysis published in Epidemiologic Reviews found that marijuana use by drivers was associated with a significantly increased risk of crash involvement. Specifically, drivers who tested positive for marijuana or self-report using marijuana were more than twice as likely as other drivers to be involved in motor vehicle crashes.

Despite this research, NIDA describes the role played by marijuana in crashes as "unclear" because marijuana can be detected in body fluids for days or even weeks after intoxication and because people frequently combine it with alcohol.

Risks to the Lungs

The U.S. Food and Drug Administration (FDA) issued a warning to consumers to stop using vaping products containing THC amid more than 1,000 reports of lung injuries—including some resulting in deaths—following the use of vaping products.

As NIDA notes, like tobacco smoke, marijuana smoke is an irritant to the throat and lungs. The substance can increase airway inflammation, airway resistance, and lung hyperinflation. And the US DEA notes that marijuana smokers experience serious health problems such as bronchitis, emphysema, and bronchial asthma.

Marijuana also contains levels of volatile chemicals and tar that are similar to tobacco smoke, raising concerns about the risk for cancer and lung disease. However, a 2012 study in Annals of the American Thoracic Society that looked at previous epidemiological studies, found that, although marijuana smoke contains a number of cancer-causing chemicals, the studies do not suggest an increased risk for the development of either lung or upper airway cancer from light or moderate use of the drug. However, the authors described the evidence as "mixed" concerning possible cancer risks of heavy, long-term use of marijuana.

Riskier to Adolescents

With their brains maturing through young adulthood, regular use of marijuana by teens may have negative and long-lasting effects on cognitive development in young people, warns NIDA. Use of marijuana also impairs short-term memory and judgment and distorts perception, which could lead to poor school or work performance. Not to mention a danger when driving while high.

Also, says NIDA, using marijuana during adolescence may lead to more problematic use of marijuana in the future or an increased risk of addiction later in life.

Cannabinoid Hyperemesis Syndrome

Cannabinoid hyperemesis syndrome (CHS) is a condition that causes cyclical nausea, vomiting, and abdominal pain after using cannabis. A 2019 study published in the Annals of Internal Medicine found that, among study participants, 18.4% of people who inhaled cannabis ended up in the emergency room of a Colorado hospital and 8.4% of those who ate edible cannabis and ended up in the emergency room had CHS symptoms.

CHS hasn't been studied extensively, said Joseph Habboushe, MD, who specializes in emergency medicine at NYU Langone. While it's possible to use marijuana for years without experiencing symptoms of CHS, once a person does experience CHS symptoms, the symptoms tend to stick around as long as the person continues using marijuana. Stopping marijuana use is the only known way to permanently alleviate CHS symptoms, but it takes time. "We know that if you stop smoking you get better, but it takes days to weeks," said Dr. Habboushe.

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This post was originally published on June 29, 2017 and has been updated for accuracy.

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