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How does marijuana affect the brain? Research Paper

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Updated: Dec 2nd, 2019


Marijuana is commonly known by other names such as pot, weed, skunk, ganja or grass. Marijuana refers to dried leaves of the cannabis plant that people smoke or eat to get the feeling of euphoria. A substance in the marijuana leaves called delta-9-tetrahydrocannabinol abbreviated as THC causes the euphoria (Steinherz & Vissing, 1997-1998; Monroe, 1998).

The abusers of the drug crave for THC, which leads to addiction. Marijuana is among the illegal drugs that are regularly used in the world. In Europe and the United States, marijuana is the leading illegal drug that many people use. Most people smoke it and teens have not been left behind in the craze for marijuana as they start smoking it early.

Studies have shown that the effects of marijuana are negative. One of the profound findings of the studies is on the negative effects of marijuana on the brain. The use of marijuana is harmful to an individual and its use should be regulated. Marijuana affects the brain and thus has an overall negative in an individual because it affects the brain, which is a vital organ in the body. It is important to note that marijuana affects other parts of the body such as the lungs but this paper will look at how marijuana affects the brain.

Theories of marijuana usage

There is a marijuana theory called the stepping stone theory. The theory asserts that the usage of marijuana often leads to abuse of other drugs. Marijuana is said to contain pharmacological properties, which induce the users to try to experiment with other drugs (Mack & Joy, 2001).

The theory applies in that if an individual will enjoy the usage of marijuana they are more likely to enjoy stronger drugs than marijuana such as cocaine. The theory presupposes that factors that lead one to start using marijuana are likely to lead to use of hard drugs. Not only does it harm an individual’s brain but also leads to further harm through the introduction to other drugs such as cocaine and heroine (Kring, Johnson, Davison & Neale, 2009).

It is important to note that not all users of marijuana end up using other drugs such as cocaine but many users of such drugs as heroine began by using marijuana (Kring et al, 2009). Moreover, people are introduced to marijuana smoking because they are told it has positive effects such as relieving one of stress but the results of the smoking are short lived as when marijuana effects wears off the issues that had caused the stress still remain and he or she must deal with problem to avoid further stress.

The other theory is the gateway theory. The theory urges that there is a consistent pattern of drug abuse from adolescence into adulthood. Young people who start the usage of marijuana are more likely to continue the habit in adulthood. The people who are able to gain access to marijuana, which is an illegal drug, also get access to other drugs hence marijuana acts as a gateway to other hard drugs as their access becomes easy (Mack & Joy, 2001).

Researches findings on effects of marijuana on the brain

Research findings on the brain show that abuse of marijuana for a long time affects the brain just as the other drugs do to the brain. The usage of marijuana affects a person general life. A study shows that the users who take high doses of marijuana report problems such as their distortion of their cognitive abilities, which include the memory. Studies also indicate that people who start smoking marijuana at an early age have higher risks of getting the negative effects because their brains are still developing.

The findings on the effects of marijuana on the brain show mixed results as some say that marijuana has no long time effects on the brain and that the short effects wear quickly. They consider marijuana to contain useful medicinal values such as alleviating nausea in cancer patients and helping them to regain their eating appetite (NIDA Infofacts: marijuana, n.d.).

In fact some groups have been calling for the legalization of marijuana because they say it does not have negative effects. Other studies have also shown that the amounts of marijuana required in causing brain damage are very high and the studies done on animals indicate that human beings have little chance of having their brains damaged through smoking of marijuana.

Some studies also indicate that use of marijuana can lead to mental problems. Individuals who use marijuana exhibit increased levels of things such as anxiety, depression, stress and schizophrenia. Evidence shows that there is a strong link between marijuana use and schizophrenia later on in life (How Does Marijuana Affect the Brain? 2010).

How marijuana travels to the brain

THC targets the brain and thus affects this vital human organ. Marijuana is often taken through inhalation via smoking and gains faster access to the bloodstream. It gains fast access to the brain because it is able to bypass the digestive process (Mehling & Triggle, 2003, p. 26). The metabolites in the drug are lipophilic- fat-soluble and are able to bypass the barrier that regulates substances that pass from the blood to the brain.

Marijuana is able to gain access to the brain and bypass two layers of cells, which act as the barrier between the blood and the brain. When marijuana gets to the brain, the users report that they feel released from stress and attain euphoria. It is important to note that the effects of marijuana depend on things such as the social setting, users experience and psychological history with the drug in association with countless personality effects and the chemical complexity of the marijuana.

The chemical complexity of marijuana depends on the part of the cannabis plant from which it is taken from for instance THC is located in resin found in the flowering tops of the cannabis plant and a small amount in the leaves. The most chemically complex marijuana is found in resin removed from the stem and the leaves. Such marijuana contains from eight to fourteen per cent of THC whereas marijuana made from dried leaves of the plant contains from four to 8 per cent of THC (Steinherz & Vissing, 1997-1998).

Effects of marijuana on the brain

The substance THC is fat-soluble and may be left in the body’s fatty tissues and later released into the bloodstream after a long period. Studies show that regular users of marijuana have a higher risk of getting their brains affected than the occasional users. Frequent users are more likely to be affected because THC takes a longer time to be released from their bodies as they accumulate large quantities of the substance in their bodies.

Studies show that use of marijuana has effects on the brain. Those who use marijuana exhibit it effects on their brains after a while and even though studies on how it affects the brain have been inconsistent, its impact on the users cannot be denied (Weinsten et al, 2007). For instance, one study shows that there is no conclusive evidence of brain damage because of marijuana usage. Nine people who underwent the study showed no sign of brain damage even after smoking about nine marijuana cigarettes from the CAT scans.

Nevertheless, many other researches have shown that the THC is responsible for altering the way in which the brain senses as well as the processing of information. The alterations are mostly notable in the region of the brain called the hippocampus. Marijuana affects the memory of an individual when taken in high doses as THC alters the way the brain functions because it has many receptors that receive the THC.

The hippocampus part of the brain has the responsibility of integrating sensory of the memory and motivation. It is also responsible with memory and the learning process. Thus, memory and learning is interfered with by marijuana usage (Mehling & Triggle, 2003). THC attaches itself on the receptors in the hippocampus and due to the fact that it is a steroid it inhibits the hippocampus from retrieving memory and especially the short term memory.

THC is responsible for weakening the short term memory through the destruction of the nerve cells. The destroyed nerve cells acquire new structures which are unable to register any new information to the brain when marijuana users take high doses. The information an individual on a high dose of marijuana may not be registered in the brain hence they cannot retrieve it from their memory. Moreover, THC reduces the ability of the nerve cells to function well (Ejelonu, 2004).

The hippocampus region of the brain contains cannabinoid receptors that receive the THC which make users feel high. The high concentration of cannaboid in the brain makes the users experiences problems with the memory as the nerves responsible for transmitting information to the brain are distorted.

The impact on the memory can affect other activities such as learning long after the effects of high doses of marijuana wear off. The users of marijuana often have lower educational attainment than their non-smoking counterparts because it affects their memory and learning process (Gruber, Pope, Hudson& Yurgelun-Todd, 2003).

Marijuana affects the memory types in two ways. The first type of the memory affected is recognition. Through the recognition memory, an individual is able to identify words Users of marijuana are able to identify words that they had seen prior to smoking marijuana and identify other words that they had not seen prior to smoking.

The mistake in recognizing words that had not been seen prior to smoking is called memory intrusions. The memory intrusions occur because the brain’s free cells are affected by THC. Smoking marijuana interferes with the ability of the user to recall words correctly from a given list. For example, smokers of marijuana are only able to remember some words in a given list.

They remember the words that they saw last and forget those that appear in first in the list. The failure to recall the words at the top of the list after a short while indicates that marijuana ahs strong effects on the brain. The THC in marijuana does not impair ones ability to recall but instead alters the way the memory works by creating selective memory where one recalls some words and not others (Ejelonu, 2004).


Marijuana use has been shown by studies to affect the brain in a number of ways. The chemical substance found in the cannabis plant called THC sticks to the cannabinoid receptors that are concentrated on the hippocampus area in the brain and changes the way the nerve cells work. The alteration of the function of the nerve cells affects how information is registered on the memory and the ability of the marijuana user to recall information.

Moreover, marijuana affects an individual’s life in a myriad ways such as in their social life, careers and even in their cognitive motor skills. The fact that some researches show that marijuana does not have harmful damages on an individual should not encourage people to experiment with the drug as there is evidence to show that it does have an effect on the brain and those effects are negative in nature apart from the short lived feelings of euphoria that lure people into the drug.

More importantly, people need to be educated on how marijuana affects the human brain and body in general so that those who decide to start or continue its use make informed choices. In addition, more studies need to be done to give conclusive information on how marijuana use affects an individual’s brain to remove the controversy surrounding the drug.

Reference List

Ejelonu, A. (2004). How does marijuana affect the brain? Web.

Gruber, A.J., Hope, H.G., Hudson, J.I. & Yurgelun-Todd, D. (2003). Attributes of long-term heavy cannabis users: a case-control study. Psychological Medicine, 33, 1415-1422.

How Does Marijuana Affect the Brain? (2010). Web.

Kring, A. Johnson, S. Davison, G.C. & Neale, J.M. (2009). Abnormal psychology. New York: John Wiley and Sons.

Mack, A. & Joy, J.E. (2001). Marijuana as medicine?: the science beyond the controversy. New National Academies Press.

Mehling, R. & Triggle, D.J. (2003). Marijuana. New York: InfoBase Publishing.

Monroe, J. (1998). Marijuana- a mind altering drug, Current Health, 24 (7), no.pag.

. (n.d.). Web.

Steinherz, K & Vissing, T. (1997-1998). . Web.

Weinstein, A et al. (2008). Brain imaging study of the acute effects of Δ9 – tetrahydrocannabinol (THC) on attention and motor coordination in regular users of marijuana. Psychopharmacology, 196 (1), 119-131.

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