Medically Reviewed by
Jason Crawford

Article Last Updated on January 1, 2023

People have known about the cannabis plant and its many uses for thousands of years. Initially, it was used in religious ceremonies, but nowadays it’s used both medicinally and recreationally, and more and more states are legalizing it. New York state has just legalized cannabis for recreational use and that made it the 15th state in the US to have done so. Today, people use medical marijuana to treat several conditions, and recreational marijuana as a way to unwind after a stressful day.

Cannabis use has increased in the United States as a result of the legalization of recreational marijuana, according to an article by the NYU School of Medicine. The popularity of cannabis continues to increase, as more and more youths are trying out vaping, smoking joints, or eating cannabis-rich edibles. So, if you’re planning on trying out the cannabis plant, you’ll definitely benefit from learning more about how THC affects the body.

The Cannabinoids in Weed (THC vs CBD)

The marijuana plant contains over 120 active ingredients, the most abundant ones being cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC). 

On the one hand, we have THC, the cannabinoid responsible for the psychoactive effects of cannabis, as well as the one that affects neurotransmitters like norepinephrine and dopamine

On the other hand, we have CBD, a non-psychoactive cannabinoid that has therapeutic and anti-inflammatory properties, and may be used to help with chronic pain, migraines, inflammation, seizures, as well as other conditions.

The Endocannabinoid System and THC

Understanding the Endocannabinoid system (ECS) is crucial to understanding how THC affects the body. The ECS is responsible for maintaining homeostasis (balance) in the body, and regulating the metabolism, appetite, short-term memory, intracellular communication, and other functions.

It consists of cannabinoid receptors, endocannabinoids, and enzymes that affect the synthesis and degradation of endocannabinoids. The effects of cannabis on the body and the central nervous system are a result of the cannabinoids binding to these cannabinoid receptors (CB1 and CB2).

Once THC enters the body, it interacts with the central nervous system and specific brain cell receptors, stimulates the reward system in the brain, and increases the levels of dopamine in the body. Since this important cannabinoid has a similar chemical structure to anandamide (a brain chemical), it can change how many neurotransmitters get released from neurons, which is why marijuana aficionados experience the high after cannabis use. However, regular users should be careful regarding how much and how often they use cannabis, as long-term cannabis use may affect the proper function in the frontal lobe

Short-Term and Long-Term Effects of THC

A review done in 2017 by the National Academies of Sciences, Engineering, and Medicine at the Health and Medicine Division in Washington DC, researched relevant studies on the therapeutic effects of cannabis and cannabinoids on the body. The committee reviewed health conditions like:

  • Cancer;
  • Chronic pain;
  • Anorexia and weight loss associated with HIV;
  • Epilepsy;
  • Spasticity as a result of MS;
  • Tourette syndrome;
  • Amyotrophic lateral sclerosis;
  • Chemotherapy-induced nausea and vomiting irritable bowel syndrome;
  • Huntington’s disease;
  • Parkinson’s disease;
  • Dementia;
  • Dystonia;
  • Glaucoma;
  • Anxiety and depression;
  • Traumatic brain injury;
  • Schizophrenia.

The review concluded that the THC present in cannabis may help ameliorate the following medical conditions:

  • Chronic pain;
  • Epilepsy;
  • Chemotherapy-induced nausea and vomiting;
  • Spasticity associated with multiple sclerosis.

The Use of Cannabis and THC to Treat Medical Conditions

Even though the use of cannabis may cause some side effects, researchers have found out that medical cannabis can be used to treat pain and illness. While the FDA still hasn’t approved THC as a treatment option, some patients use it in states where weed is legal.

THC can be used medicinally to help with the following conditions:

  • Pain relief for patients suffering from chronic pain;
  • Reduction in nausea and vomiting as a result of chemotherapy;
  • Treatment option for Multiple Sclerosis (MS);
  • Treatment option for epilepsy.

The  effects of cannabis and its cannabinoids THC and CBD, have also been researched for conditions like:

  • Alzheimer’s disease;
  • Crohn’s disease;
  • Diseases that affect the immune system;
  • Eating disorders (Anorexia);
  • Mental health conditions (Schizophrenia and PTSD); 
  • Muscle spasms;
  • Wasting syndrome (cachexia).

What Are the Medical Benefits of THC?

THC is highly used recreationally, however, medicine has started researching its use for treating medical conditions. Below we’ll go over a few ways that THC is used medicinally for:

  • Treating digestive disorders – THC can soothe pain and reduce nausea which is beneficial for treating symptoms of gastrointestinal distress. Therefore, it can be used to help people with irritable bowel syndrome, Chron’s, and other GI-tract diseases.
  • Treating sleep disorders – toking to help with insomnia is a common use of marijuana, though it may provide other long-term side effects with continuous use.
  • Treating chronic pain – THC is a pain-reliever and as such it’s used to help patients with constant neuropathic pain, but also used for temporary muscle soreness.
  • Cancer treatments – THC can be used as a treatment for patients that undergo chemotherapy and radiation since it helps mitigate the side effects.
  • Its anti-inflammatory properties – it can help with autoimmune diseases and neurodegenerative disorders like MS since it affects the immune system.

Recreational Cannabis Use

Apart from its medical use, recreational use of marijuana is quite popular, especially among youths. Cannabis has been their go-to recreational drug at parties, after stressful exams, or after a particularly hard day at work.

However, a 2014 study done by the San Diego Healthcare System, reviewed how cannabis use in adolescence may result in “disadvantages in neurocognitive performance, macrostructural and microstructural brain development, and alterations in brain functioning.”

Side Effects of THC and Marijuana Use

While cannabis can be used to treat medical conditions, the use of marijuana and the presence of THC in it may also lead to a number of short-term and long-term negative effects on users. (National Institute on Drug Abuse , 2019) 

The most common short-term side effects include:

  • Anxiety, paranoia, panic, hallucinations;
  • Problems with short-term memory;
  • An increased risk of stroke and heart attack because of an increased heart rate;
  • Impairment on reaction time and motor coordination that may impact your driving ability;
  • Dry mouth and red eyes.

On the other hand, repeated use of cannabis over a longer period of time may lead to the following long-term effects:

  • Addiction;
  • Decline in IQ if you’ve started consuming cannabis as an adolescent;
  • Higher possibility for opiate abuse, as well as other drugs;
  • Lower attention span;
  • Progressive decline of the immune system;
  • Apathy and loss of motivation;
  • Increased risk of bronchitis, lung infections, and cardiovascular problems;
  • Anxiety and depression that can lead to more serious mental health issues.

Most of these effects are a result of the presence of THC and other cannabinoids. CBD, on the other hand, is tolerated pretty well, even in large doses. The only side effects that can come from CBD are pretty minor, and they include:

  • Fatigue;
  • Weight loss;
  • Dizziness;
  • Diarrhea.

Finally, no cannabinoid found in weed is lethal, so there are no recorded deaths as a result of marijuana overdoses.

Final Thoughts on the Effects of THC on Users

The effects of cannabis Sativa on users can be positive or negative, depending on the consumed dose, how often they consume it, as well as the other underlying medical conditions that users may have. If you’ve been thinking about whether you should tell your GP or other health professionals about your marijuana use, the answer is definitely yes.

As a result of confidentiality laws, your doctor won’t be able to tell anyone else about your recreational habits concerning weed, though they might need to know whether you’ve been using it (to be able to make a proper diagnosis). And if you’ve been planning to use THC to treat a medical condition, it’s even more important for your doctor to get the whole picture.

Additional Sources

NIDA. 2019, December 24. Marijuana DrugFacts. Retrieved from https://www.drugabuse.gov/publications/drugfacts/marijuana on 2021, March 30

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.