Fraser Horton
Fraser Horton
Last Updated on July 19, 2021

Marijuana has quickly become the most widely used controlled substance around the world, its use being especially prevalent among young adults. Due to its myriad of effects on the human body, anti-inflammatory, psychotropic, and sedative being some of them, the cannabis plant is used both for medicinal and recreational purposes.

In this article, we’ll be focusing on what effects weed has on those who use it, including how it affects the brain, so read on if you’re interested in finding out more about this particular subject. 

The Endocannabinoid System and How Cannabis Affects It

The endocannabinoid system (ECS) is responsible for regulating the metabolism, appetite, memory, intracellular communication, and overall balance (homeostasis) in the body. The way cannabis produces its effects on users is by interacting with the endocannabinoid system.

Once weed gets into our system, it affects the cannabinoid receptors (CB1 and CB2) which are a part of the ECS along with the endocannabinoids and enzymes that degrade the endocannabinoids. Once the cannabinoids in weed bind to the receptors in the ECS, marijuana produces its effects on the central nervous system. Therefore, once the psychoactive cannabinoid tetrahydrocannabinol (THC) enters the bloodstream, the receptors are responsible for producing its psychoactive effects.  (National Institute on Drug Abuse (NIDA), 2021)

Cannabinoids and Other Chemical Compounds Found in Weed

The cannabis plant consists of more than 400 chemical compounds, among which you can find the sedative cannabinoid cannabidiol (CBD), the psychoactive cannabinoid tetrahydrocannabinol (THC), other cannabinoids, and terpenes. The terpenes are responsible for the aroma and flavor of weed, and the cannabinoids are responsible for the effects of weed on the central nervous system. 

Some of the cannabinoids, like THC, produce the sought-after feelings that cannabis consumers experience, including:

  • Euphoria;
  • Relaxation;
  • Energy;
  • Happiness;
  • Creativity;
  • Heightened sensitivity to sound, touch, light, and smell. 

THC and the Human Brain

The pleasurable high that marijuana users get after smoking weed is a result of the interaction between the central nervous system and a cannabinoid found in weed – THC. As a cannabinoid, THC affects how many neurotransmitters will get released from neurons.

On the one hand, THC stimulates the brain’s reward system, and on the other hand, it increases the levels of dopamine in the body. Dopamine is a vital chemical messenger that’s involved in regulating body movements, motivation, short-term memory, attention, and reward processes throughout the body, which is why most users feel pleasure after consuming weed. 

Even though a lot of users have a positive experience with cannabis, long-term cannabis use may cause a dysfunction in the frontal lobe, disrupt the function of the hippocampus and orbitofrontal cortex, which means it affects focus and the creation of new memories. Another part of the body that THC affects is the function of the cerebellum and basal ganglia that are responsible for coordination, reaction time, and balance. For this particular reason, it’s best for people under the influence of marijuana not to drive.

The Effects of Marijuana on the Brain

Cannabis use can cause a list of short-term and long-term effects. While most recreational users consume cannabis as a way to unwind and relax, and medical cannabis users take medical marijuana as a treatment for a medical condition, weed can cause a number of effects on the brain. (National Institute on Drug Abuse (NIDA), 2021)

Short-Term Effects of Marijuana

The short term effects of marijuana use on the brain include:

  • Short-term memory problems;
  • Moderate to severe anxiety, paranoia, panic, psychosis, hallucinations;
  • Impaired coordination and lowered reaction time (which can cause problems while driving and operating heavy machinery).

Long-term Effects of Marijuana

Marijuana use over time can lead to a wide range of effects on the brain and impair brain development. Long-term cannabis use can increase your risk of substance abuse disorders, mental health disorders, and cause you to have problems with concentration and memory.

Studies on the Effects of Cannabis on the Brain

Some marijuana studies show that regular marijuana use during adolescence can cause a reduction in executive functions like learning, memory, impulse controls, and other functions, compared to people who don’t use weed. Other studies haven’t found significant differences among people who do and don’t consume cannabis. Below, we’ll go over the most important effects of cannabis on the brain.

Marijuana, Brain Development, and IQ

According to a 2012 study done at Duke University, cannabis use may impair brain development and cause a loss of IQ, therefore causing lasting mental deficits that affect the learning ability of youths.

Another longitudinal study done in New Zealand found out that long-term marijuana use as an adolescent can cause a loss of IQ between 6-8 points in early adulthood, and heavy marijuana users might not recover the lost IQ points. 

Marijuana and the Reward System

A recent study showed that chronic marijuana users exhibited more activity in the brain region responsible for the rewards when they were shown photos of cannabis paraphernalia, compared to when they were shown photos of their favorite fruit. Non-users, on the other hand, didn’t show a great activity in this region when they were shown marijuana-related objects.

Effects of Cannabis on the Adolescent Brain

A study done on young adult cannabis users (ages 20–24) for 8 consecutive years, showed that heavy marijuana use can cause memory deficits and a delayed verbal memory compared to non-users. However, those who quit marijuana had an improved performance over the next 8 years. (Jacobus et al, 2014)

Marijuana, Psychosis, and Schizophrenia

Consuming marijuana for a long time causes an increased risk for psychosis and doubles the risk of developing schizophrenia later in life according to a 2020 study. Daily marijuana use, as well as using high THC strains, may increase the risk of developing a psychotic illness by as much as five times. 

Final Thoughts

While weed can efficiently treat a number of medical conditions and give euphoric feelings to recreational users, the long-term effects of marijuana on the brain are still researched. Therefore, we can’t reach any definitive conclusions as of yet. 

The National Institutes of Health is doing a major longitudinal study called ABCD (Adolescent Brain Cognitive Development study) focused on tracking young Americans from late childhood to early adulthood with the use of neuroimaging. The study will be able to clarify how marijuana and other substances may affect adolescent brain development.

Ultimately, no matter what the substance is, if people are consuming it in huge quantities, there will always be some side effects – and the same goes for marijuana use.

Additional Sources

NIDA. 2021, April 13. How does marijuana produce its effects?. Retrieved from https://www.drugabuse.gov/publications/research-reports/marijuana/how-does-marijuana-produce-its-effects on 2021, May 7

NIDA. 2021, April 13. What are marijuana’s long-term effects on the brain?. Retrieved from https://www.drugabuse.gov/publications/research-reports/marijuana/what-are-marijuanas-long-term-effects-brain on 2021, May 10

Jacobus, J., & Tapert, S. F. (2014). Effects of cannabis on the adolescent brain. Current pharmaceutical design, 20(13), 2186–2193. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3930618/

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