Pros and Cons of Weed—11 Possible Effects on Your Health

As more states legalize marijuana, it's important to know the pros and cons of pot—dope, weed, chronic, grass, and the many other names it is known as—and what effect it might have on your health. With its increasing use, Health looked at recent research and spoke with several experts to learn about the risks and benefits of smoking marijuana on your health.

The U.S. Drug Enforcement Administration (DEA) lists marijuana and its cannabinoids (biologically active components in marijuana) as Schedule I controlled substances. This 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 U.S. Food and Drug Administration (FDA) for medical use. But the use of marijuana to treat some medical conditions is legal under state laws in many states.

It May Help (or Aggravate) Anxiety

Cannabis smokers often report using the drug to relax or relieve emotional stress. A 2017 study published in Drug and Alcohol Dependence found that a very low dose of THC (the primary 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 the 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, Childs said, to determine appropriate dosages and delivery methods and prevent the opposite effects.

Quantity and experience of the user matter, per 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 (there are several different strains of marijuana), or the person is inexperienced.

Additionally, according to NIDA, people who have taken large doses of marijuana may experience acute psychosis. Symptoms of acute psychosis can include hallucinations, delusions, and a loss of the sense of personal identity.

It Can Relieve Chronic Pain and Nausea

Pain relief is a common reason people use medical marijuana. The National Academies of Sciences, Engineering, and Medicine concluded in 2017 that good evidence exists 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 Epilepsy May 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.

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. According to an article published in the British Journal of Clinical Pharmacology in 2022, data on neurodevelopmental effects on the fetus, child, and adolescent brain suggests that THC should not be used in the pediatric (and even young adult) age range.

Marijuana 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 2017 review published in Trends in Neurosciences, researchers concluded that cannabinoids might 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. For instance, per NIDA, one study using long-term data found that adults who reported marijuana use were more likely than adults who did not use marijuana to develop an alcohol use disorder within three years. In animal experiments (studies performed on animals, not humans), 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 cancer cells growing in lab dishes. Some animal studies also suggest certain cannabinoids may slow growth and reduce the spread of some forms of cancer.

In a 2019 review of the scientific literature published in the Journal of the Association of Basic Medical Sciences, researchers found that cannabinoids were able to slow tumor growth in different cancer models (cell culture and animal studies). However, these anticancer effects appear to depend on the cancer type and drug dose.

It Can Pose Risks to the Baby During Pregnancy

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, according to NIDA. For example, research shows that pregnant people who use marijuana have a 2.3 times greater risk of stillbirth, per the NIDA.

The American College of Obstetricians and Gynecologists (ACOG) recommended that obstetrician-gynecologists counsel people against using marijuana while trying to get pregnant, during pregnancy, and while breastfeeding, based on the potential of marijuana to negatively impact the developing brain of the fetus. ACOG also stated that there's no evidence that marijuana helps with 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 don't always quit. The analyses found that children's self-reported marijuana use from age 10 to 21 and alcohol use from age 6 to 21 were related to their parents' lifetime marijuana use. Children of parents with chronic or adolescent-limited marijuana use were most likely to use marijuana or alcohol themselves. Children of chronic marijuana users were also more likely to use cigarettes, report more favorable views on marijuana, or exhibit externalizing behavior and lower grades, as noted by the NIDA.

It May Increase the Risk of Heart Attack

According to the NIDA, there is evidence that a person's risk of a heart attack during the first hour after smoking marijuana is nearly five times their 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 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 the widespread availability of highly potent synthetic cannabinoids for recreational use. The authors concluded these factors have led to a rise in severe cardiovascular incidents reported, including myocardial infarction (heart attack), cardiomyopathy (heart disease affecting the muscles in the heart), arrhythmias (irregular heartbeat), stroke, and cardiac arrest (when the heart stops).

It's Not Safe to Use Marijuana and Drive

According to the 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, 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 2021 meta-analysis published in Frontiers in Psychiatry found that studies consistently indicated a slightly but significantly increased risk of crashes after acute cannabis use. The authors noted that some studies showed a significant correlation between high THC blood concentrations and car crash risk.

Despite this research, the NIDA described 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.

It Can Be Harmful to the Lungs

The U.S. Food and Drug Administration (FDA) warned 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. A 2021 study in the Journal of Adolescent Health confirmed that vaping is more likely to cause lung damage than smoking marijuana with long-term use.

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

Marijuana also contains volatile chemicals and tar similar to tobacco smoke, raising concerns about the risk for cancer and lung disease. A 2016 study published in Advancements in Clinical Research reviewed past studies and concluded that smoking cannabis posed a potential risk for developing lung cancer. However, the association between smoking cannabis and the development of lung cancer was not decisive.

It Is Riskier for Adolescents To Use

With their brains maturing through young adulthood, regular use of marijuana by teens may have harmful, and long-lasting effects on cognitive development in young people warned NIDA. The 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, per 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.

It Can Cause Cannabinoid Hyperemesis Syndrome

Cannabinoid hyperemesis syndrome (CHS), according to the National Library of Medicine, StatPearls, 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 a hospital emergency room 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, an emergency medicine physician associated with Weill Cornell Medicine. 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 alleviate CHS symptoms permanently, but it takes time. "We know that if you stop smoking, you get better, but it takes days to weeks," said Dr. Habboushe.

Summary

If you use marijuana, it's important to understand how it may affect you. Marijuana has been demonstrated to be helpful for some health conditions but is contraindicated in other situations. Furthermore, keep in mind that despite the perception that vaping marijuana is safer than smoking it, vaping is harsher on the lungs.

If you have any concerns about marijuana use and its potential harm, talk to your healthcare professional.