Medically Reviewed by
Jason Crawford

Article Last Updated on January 17, 2023

Decreasing the levels of drug use has always been a matter of public health, especially when it comes to hard drugs and opiates. However, as new legalization laws are passed and the cannabis plant is legal in more states across the US, cannabis use has increased even more. Recently, New York became the 15th state to legalize cannabis in the US, and more states will probably follow soon.

The popularity of cannabis and the recreational use of marijuana will only continue to increase as a result of legalization laws. Cannabis users are going for their old and tried joints, bongs, and weed brownies, but they’re also vaping, using tinctures, and THC pills. Medical marijuana is also on the rise, and more so after the passing of the 2018 Farm Bill

With so much fuss over the cannabis Sativa and Indica plants, you might wonder how they affect the body, and you wouldn’t be the first. So, let’s go over the effects that THC has on the body, as well as the health effects that come from cannabis use.

The Main Cannabinoids (THC vs CBD)

Out of all the active ingredients in the marijuana plant, the most popular ones are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). We thank the former for the psychoactive effects of cannabis, and the latter for the non-psychoactive, therapeutic, and anti-inflammatory properties. 

However, none of the effects of cannabis would be recognized by the body without the endocannabinoid system (ECS). It’s the system that’s most responsible for the effects of the cannabinoids in our body, and how they affect our metabolism, short-term memory, appetite, and other functions.

The ECS is made up of cannabinoid receptors (CB1 and CB2), endocannabinoids, and enzymes in charge of synthesis and degradation of the endocannabinoids. The receptors are located all over the body and in specific regions in the brain. They’re the ones that need to get stimulated in order for users to experience the effects of cannabis. 

Nowadays, cannabis is known for its medical use for treating conditions like:

  • Chronic pain;
  • Nausea and vomiting as a result of chemotherapy;
  • Multiple Sclerosis (MS);
  • Epilepsy.

In order to know more about the medical benefits of cannabinoids, the National Institute of Health (NIH) is funding more research into possible medicinal uses of THC and CBD.

The Effects of THC on the Body

THC can produce a wide array of effects on the body and the systems it’s made up of.

Respiratory System

Similar to tobacco smoke, marijuana smoke is made up of chemicals like ammonia, hydrogen cyanide, and others that may irritate the bronchial passages. Regular cannabis users are more likely to cough, produce phlegm, and have an increased risk of lung infections and bronchitis. 

More research is needed on the subject of marijuana smoke causing lung cancer. On the one hand, the National Institute on Drug Abuse (NIDA) claims that there’s no conclusive evidence with regards to marijuana smoke causing cancer, but on the other hand, marijuana smoke contains carcinogens that may increase the risk of lung cancer.

Circulatory System

Once you smoke, ingest, or apply cannabis to your skin, THC will ultimately end up in the bloodstream. After it starts circulating around the body via the bloodstream, it may increase your heart rate, and for patients who have heart disease, it may end up causing a heart attack.

On the other hand, THC in the body can lower eye pressure, and with the help of the active ingredients, it may ease the symptoms of glaucoma for a couple of hours, though more research needs to be done on the subject.

Long-term cannabis use may help reduce cancerous tumors by stopping the growth of blood vessels that feed the tumors. This is a fairly new area of research, and more study is needed in order for healthcare physicians to be able to recommend cannabis as a treatment option for cancer.

Central Nervous System

The effects of marijuana are probably most extensive when it comes to the central nervous system (CNS). THC is known to ease chronic pain, inflammation, and control seizures. It’s also responsible for the psychoactive effects that cannabis has on users who feel euphoria, relaxation, and heightened senses. The presence of THC in the body affects the “feel good” neurotransmitters in the body like norepinephrine and dopamine which is the reason behind the feelings of euphoria mentioned above.

This cannabinoid affects the hippocampus, responsible for memory, so it’s rather hard to form new memories while under the influence of weed. Balance, coordination, and reflex response are also affected by consuming weed, so marijuana users are advised against driving after consuming cannabis.

Marijuana with high concentrations of THC can affect the mental health of users by causing hallucinations or delusions. Finally, for people younger than 25 years who consume cannabis on a regular basis, it may cause alterations in brain function, like lasting impact on thinking and memory.

Digestive System

Smoking marijuana often results in a case of the munchies, hence its use for improving eating habits and reducing nausea in patients treated with chemotherapy. Inhaling marijuana may also cause slight discomfort to smokers in the form of a stinging or burning sensation in the mouth and throat.

Short Term and Long-Term Effects of THC

Cannabis use can cause health problems, some of them short-term, and others long-term. While cannabinoids like CBD cause mild and sedative effects, THC can cause some of the following effects as a result of constant use.

Short Term Effects 

  • Short-term memory problems;
  • Severe anxiety, paranoia, panic, psychosis, hallucinations;
  • Increased heart rate;
  • Impaired coordination and lowered reaction time;
  • Problems with sexual performance in males.

Long-term Effects

Marijuana use may have a wide range of side effects, both physical and mental. We’ll explore both of them below.

Physical Effects

  • Breathing problems. Marijuana smoke irritates the lungs, so it can cause long-term breathing problems that make it more likely for users to develop lung infections or even lung cancer.
  • Increased chances for getting a heart attack. Marijuana increases the heart rate of users for up to 3 hours after smoking. The increased heart rate may result in a heart attack, especially in older people and people with heart problems. 
  • Problems with child development during and after pregnancy. Marijuana use during pregnancy may be associated with affective symptoms and ADHD according to a 2020 study.
  • Intense nausea and vomiting. Extensive long-term marijuana use can lead to the development of Cannabinoid Hyperemesis Syndrome. This syndrome causes users to experience nausea, vomiting, and dehydration.
  • Marijuana affects brain development. Adolescent cannabis use may impair brain development, learning abilities, and loss of IQ, according to a study done at Duke University. 
  • Vaping may affect lung health. Vaping has been associated with acute lung injury which resulted in several deaths, according to research done by the University of California.

Mental Effects

Long-term marijuana use with high levels of THC may be the reason for mental disorders like: 

  • Temporary hallucinations;
  • Temporary paranoia;
  • Worsening of mental health disorders like depression and anxiety;
  • Worsening of symptoms in patients with schizophrenia. 

Final Thoughts on the Effects of THC on the Body

This cannabinoid is the main reason why a lot of users come back to cannabis over and over. It not only produces euphoric effects and affects feel-good hormones like dopamine and norepinephrine, but it may also provide health benefits to users. THC and other cannabinoids present in weed can alleviate chronic pain, help with seizures and MS, reduce nausea and vomiting in patients undergoing chemo, and provide other benefits. 

However, long-term substance use sometimes results in addiction, and that’s often the case with marijuana use. Moreover, about 30 percent of marijuana users will eventually develop a marijuana use disorder, and trying to quit may result in symptoms like irritability, insomnia, loss of appetite, depression, anxiety, and others.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.