Examination of Marijuana’s Short- and Long-Term Effects on the Brain

By Abimbola Farinde posted 14 days ago


Marijuana History to Date

It can be difficult for some to understand the transition that marijuana has undergone in American society and culture over the last few years. Many states have moved toward the legalization of the drug for medical and/or recreational use even though legal marijuana use has been a controversial topic in the United States for decades (Tackett 2019).

The origins of marijuana stem from the cannabis plant—specifically, the dried flowers of Cannabis sativa. It is commonly smoked, but it also can be eaten, brewed in tea, or mixed with other foods (Bridgeman and Abazia 2017; Tackett 2019). Cannabis is a widely cultivated and used drug around the world, being consumed by approximately 147 million people, or 2.5% of the global population, annually (Bridgeman and Abazia 2017).

General Effects of Marijuana

The effects of marijuana have largely been tied to its effect on the central nervous system, most notably the brain through memory, thinking, and perception given that its main psychoactive ingredient, tetrahydrocannabinol (THC), works to stimulate the parts of the brain that elicit pleasure. The release of dopamine produces the euphoric and tranquil feeling that users experience with marijuana consumption (NIH 2020). The general effects of marijuana are experienced through smoking and vaping, as well as through cooking the plant, using it as part of an oil, or brewing it with teas (Fletcher 2019).

Short-Term Effects of Marijuana on the Brain

The psychoactive effects of marijuana can be experienced immediately after smoking, with the potential for intoxication occurring after 30 minutes and lasting for many hours (Crean, Crane, and Mason 2011). Acute effects of cannabis on executive function can be experienced immediately and can produce some degree of impairment. The use of THC can alter the functioning of the hippocampus and orbitofrontal cortex, which are important for the formation of new memories and for allowing an individual to alter their attentional focus (NIH 2020). The attachment of THC receptors to these parts of the brain can cause an activation in the brain that can have a negative effect on mental functioning, can impair thinking, and can result in difficulty learning and performing complex tasks (NIH 2020). Furthermore, THC also can affect the cerebellum and basal ganglia, resulting in issues with posture, coordination, and a person’s reaction time. If either a large dose is taken or the user consumes high-potency marijuana, an individual can experience myriad acute effects, which include impaired motor coordination and balance, as well as panic (anxiety); also, there is the potential for acute psychosis to develop, which can manifest as delusions or hallucinations (NIH 2020). In general, the most common effect that people experience is a sense or feeling of being “high” that can alter their senses, perception of time, and problem-solving ability, as well as impair memory (Fletcher 2019).

Long-Term Effects of Marijuana on the Brain

The current understanding is that the long-term effects of marijuana on health and behavior are more limited when compared with the acute effects. There is an increased risk of psychotic disorders (including schizophrenia) in those users with a predisposition (Volkow et al. 2014).

It also has been recognized that marijuana has the potential to affect the developing brain. If use is initiated at a young age, it has the ability to impact memory, thinking, and learning ability and induce cognitive impairment, with lower IQ levels being observed in those individuals who were frequent users of marijuana during adolescence (Volkow et al. 2014).

Research on how chronic marijuana use can affect the structure of the human brain has not been consistent, but there have been studies showing brain structure abnormalities in cannabinoid 1 (CB1) receptor–enhanced areas of the brain (Rapp et al. 2012). The long-lasting effects of marijuana use are still being studied to determine if some effects can be reversed. Research has shown that cannabis-caused impairments in executive function can be present up to three weeks or more after use of the substance. Upon cessation, attentional and working memory can return to normal, but the most notable impairments may be observed in decision-making, concept formation, and planning (Crean, Crane, and Mason 2011).


While marijuana appears to be associated with potential adverse effects on the brain, it appears to be a drug that is here to stay. It can interfere with cognitive function and motor function, and repeated use during adolescence can result in lasting alterations in brain function (Volkow et al. 2014). These are factors that should always be taken into consideration by an individual who makes the decision to initiate marijuana use. The risk versus benefit of use should always be evaluated regardless of whether it is being used for medical or recreational purposes.

The information presented in this article represents the views of the author. The Society of Toxicology has not vetted or reviewed the science presented herein, nor does posting this article represent any proposal or endorsement of any position by the Society.


Bridgeman, Mary Barna, and Daniel T. Abazia. 2017. “Medicinal Cannabis: History, Pharmacology, and Implications for the Acute Care Setting.” Pharmacy & Therapeutics 42, no. 3: 180–88.

Crean, Rebecca D., Natania A. Crane, and Barbara J. Mason. 2011. “An Evidence-Based Review of Acute and Long-Term Effects of Cannabis Use on Executive Cognitive Functions.” Journal of Addiction Medicine 5, no. 1: 1–8.

Fletcher, Jenna. 2019. “How Marijuana Affects the Body.” Medical News Today. Accessed July 1, 2020.

NIH (National Institutes of Health). 2020. “How Does Marijuana Produce Its Effects?” National Institute on Drug Abuse. Accessed July 1, 2020.

Rapp, Charlotte, Hilal Bugra, Anita Riecher-Rössler, Corinne Tamagni, and Stefan Borgwardt. 2012. “Effects of Cannabis Use on Human Brain Structure in Psychosis: A Systematic Review Combining In Vivo Structural Neuroimaging and Postmortem Studies.” Current Pharmaceutical Design 18, no. 32: 5070–80.

Tackett, Brittany. 2019. “History of Marijuana.” Accessed July 1, 2020.

Volkow, Nora D., Ruben D. Baler, Wilson M. Compton, and Susan R. B. Weiss. 2014. “Adverse Health Effects of Marijuana Use.” New England Journal of Medicine 370, no. 23, 2219–27.