Marijuana is made from the shredded and dried parts of the cannabis plant, including the flowers, seeds, leaves, and stems. It’s also known as pot, weed, hash, and dozens of other names. While many people smoke or vape it, you can also consume marijuana as an ingredient in food, brewed tea, or oils. Different methods of taking the drug may affect your body differently. When you inhale marijuana smoke into your lungs, the drug is quickly released into your bloodstream and makes its way to your brain and other organs. It takes a little longer to feel the effects if you eat or drink marijuana. There is ongoing controversy around the effects of marijuana on the body. People report various physical and psychological effects, from harm and discomfort to pain relief and relaxation.
Marijuana can be used in some states for medical reasons, and in some areas, recreational use is legal as well. No matter how you use marijuana, the drug can cause immediate and long-term effects, such as changes in perception and increased heart rate. Over time, smoking marijuana may cause a chronic cough and other health issues. The effects of marijuana on the body are often immediate. Longer-term effects may depend on how you take it, how much you use, and how often you use it. The exact effects are hard to determine because marijuana has been illegal in the U.S., making studies difficult and expensive to conduct. But in recent years, the medicinal properties of marijuana are gaining public acceptance. As of 2017, 29 states plus the District of Columbia have legalised medical marijuana to some extent. The tetrahydrocannabinol (THC) and another ingredient called cannabidiol (CBD) are the main substances of therapeutic interest. The National Institutes of Health-funded research into the possible medicinal uses of THC and CBD, which is still ongoing. With the potential for increased recreational use, knowing the effects that marijuana can have on your body is as important as ever. Read on to see how it affects each system in your body.
Much like tobacco smoke, marijuana smoke is made up of a variety of toxic chemicals, including ammonia and hydrogen cyanide, which can irritate your bronchial passages and lungs. If you’re a regular smoker, you’re more likely to wheeze, cough, and produce phlegm. You’re also at an increased risk of bronchitis and lung infections. Marijuana may aggravate existing respiratory illnesses, such as asthma and cystic fibrosis. Marijuana smoke contains carcinogens so that it may increase your risk of lung cancer too. However, studies on the subject have had mixed results. According to the National Institute of Drug Abuse (NIDA), there is no conclusive evidence that marijuana smoke causes lung cancer. More research is needed.
THC moves from your lungs into your bloodstream and throughout your body. Within minutes, your heart rate may increase by 20 to 50 beats per minute. That rapid heartbeat can continue for up to three hours. If you have heart disease, this could raise your risk of heart attack. One of the tell-tale signs of recent marijuana use is bloodshot eyes. The eyes look red because marijuana causes blood vessels in the eyes to expand. THC can also lower pressure in the eyes, which can ease symptoms of glaucoma for a few hours. More research is needed to understand the active ingredients in marijuana and whether it’s a good treatment for glaucoma. In the long term, marijuana has a possible positive effect on your circulatory system. Research isn’t conclusive yet, but marijuana may help stop the growth of blood vessels that feed cancerous tumours. Opportunities exist in both cancer treatment and prevention, but more research is needed.
Central nervous system
The effects of marijuana extend throughout the central nervous system (CNS). Marijuana is thought to ease pain and inflammation and help control spasms and seizures. Still, there are some long-term negative effects on the CNS to consider. THC triggers your brain to release large amounts of dopamine, a naturally occurring “feel good” chemical. It’s what gives you a pleasant high. It may heighten your sensory perception and your perception of time. In the hippocampus, THC changes the way you process information, so your judgment may be impaired. The hippocampus is responsible for memory, so it may also be difficult to form new memories when you’re high. Changes also take place in the cerebellum and basal ganglia, brain areas that play roles in movement and balance. Marijuana may alter your balance, coordination, and reflex response. All those changes mean that it’s not safe to drive. Very large doses of marijuana or high concentrations of THC can cause hallucinations or delusions. According to the NIDA, there may be an association between marijuana use and some mental health disorders like depression and anxiety. More research is needed to understand the connection. You may want to avoid marijuana if you have schizophrenia, as it may make symptoms worse. When you come down from the high, you may feel tired or a bit depressed. In some people, marijuana can cause anxiety. About 30 percent of marijuana users develop a marijuana use disorder. Addiction is considered rare, but very real. Symptoms of withdrawal may include irritability, insomnia, and loss of appetite. In people younger than 25 years, whose brains have not yet fully developed, marijuana can have a lasting impact on thinking and memory processes. Using marijuana while pregnant can also affect the brain of your unborn baby. Your child may have trouble with memory, concentration, and problem-solving skills.
Smoking marijuana can cause some stinging or burning in your mouth and throat while you’re inhaling. Marijuana can cause digestive issues when taken orally. For example, oral THC can cause nausea and vomiting because of the way it’s processed in your liver. It may also damage your liver. Conversely, marijuana has also been used to ease symptoms of nausea or upset stomach. An increase in your appetite is common when taking any form of marijuana, leading to what many call “the munchies.” This is considered a benefit for people being treated with chemotherapy for cancer. For others who are looking to lose weight, this effect could be considered a disadvantage.
THC may adversely affect your immune system. Studies involving animals showed that THC might damage the immune system, making you more vulnerable to illnesses. Further research is needed to fully understand the effects.
Credit: Ann Pietrangelo and Kristeen Cherney for HealthLine, 21 July 2017
Medically reviewed by Timothy J. Legg, PhD, PsyD, CRNP, ACRN, CPH.