Marijuana: Effects on the Brain

By at December 1, 2010 | 1:09 pm | Print

Marijuana: Effects on the Brain

Marijuana and its Effects on the Brain
Written by Cristina Wright

According to the National Institute of Drug Abuse, marijuana is the most commonly abused illicit drug in the United States.  Statistics show that among teenagers 12-17 years old, the average age of first marijuana usage is 14 years old. Marijuana is thought to be the one drug that is safe to use; everyone uses it and you do not get addicted. At least that’s what some would like to think. (”Marijuana”) Furthermore, we will learn the basics of marijuana, the chemicals involved in producing such a drug and how it affects the brain.

About 40 years ago, researchers discovered that a compound called THC was the element responsible for marijuana’s effects.  The most common chemical in marijuana is called “delta-9 tetrahydrocannabinol” or as many of us know it as, “THC”.  It also contains about four hundred other chemicals as well.  The THC in marijuana is what causes the altered states of consciousness, as well as induces relaxation and heightens the senses. All forms of marijuana are mind-altering or psychoactive.  In other words, they change how the brain works.  Marijuana’s effects on the user all depend on its strength or potency, which is the amount of THC contained in the plant. (Chudler)  In the year 2006, the NIDA’s results showed that most marijuana contained, on average, 7 percent of THC. (“Marijuana”)  The THC acts on cannabinoid receptors which are found on neurons in many places in the brain.  These specific brain areas are involved in memory, concentration, perception and movement.  The authors reported that THC administration increased subjective ratings of euphoria, dysphoria, somatic effects and sedation; decreases in intellectual efficiency and energy were also noted. (Gruber 140) Once THC activates to the cannabinoid receptors, it begins to impair the normal functioning of these brain areas.  “Because it is a steroid, THC acts on the hippocampus and inhibits memory retrieval.” (Ejelonu ) This substance causes a relaxation of the smooth muscles in the arteries, which is most readily seen in the blood vessels of the eyes causing users to have “bloodshot eyes”.  Other causes include reduced coordination, disruption in attention, reduced blood pressure.  However, in high doses marijuana can cause such things like hallucinations, delusions, impaired memory and disorientation.  The amount of time the THC stays detected in one’s system all depends on how much a person has smoked, how long they have been smoking for, and the method used to detect THC.  It can be detected in urine, blood and saliva. The half-life of THC is about 24 hours.  The metabolites of THC can be detected for 45 to 60 days after the last use (Ejelonu).

Marijuana comes from a plant called “Cannabis sativa.”  Marijuana refers to the dried leaves, stems, seeds and flowers of the cannabis plant.  Generally, it is a mixture of brown, green, or even gray in color and sometimes resembles tobacco products.  There is also low quality versus high quality marijuana.  Lower quality usually consists of all parts of the cannabis plant, and higher quality is mainly the buds and flowering top of the plant itself.  Marijuana has a lot of street names; some of those include chronic, dope, 420, ganja, KGB (killer green bud) and Mary Jane. The list goes on and on, but these are the most common names to people in our society nowadays. All in all, marijuana is a dangerous drug causing mind altering states while under its influence (Chudler).

Typically, marijuana is used in three different ways.  Users typically smoke it as a cigarette, known as a joint, or smoke it in a pipe or water pipe, referred to as a bong.  Another way people smoke marijuana is through a blunt, in which you slice open a cigar and replace the tobacco with marijuana.  It has also been said that people mix the marijuana into foods or use it to brew a tea (Chudler).

In 1992, scientists figured out why the brain has such cannabinoid receptors; anandamide.  Anandamide is the brain’s own THC.  THC can affect two neurotransmitters: norepinephrine and dopamine.  Serotonin and GABA levels may also be altered.  As THC affects the production and release of such neurotransmitters, it stimulates certain regions of the brain, which produce a pleasurable excitement.  Therefore, users begin to feel a sense of elated happiness.  The effects of marijuana have been seen to last for several days or weeks.  Once the user feels the initial stage of being high, it is soon followed by the user feeling depressed or sleepy.  Research shows that marijuana abuse can also produce anxiety or panic attacks, along with a sense of fear and distrust (Chudler).

Going a little more in depth, these chemicals disrupt the way nerve cells normally send, receive, and process information.  Drugs are able to this by imitating the brain’s natural chemical messengers and/or by over stimulating the “reward circuit” of the brain.  Because marijuana has a similar structure to chemical messengers (neurotransmitters), it is able to trick the brain’s receptors and activate nerve cells to send abnormal messages.  The drug targets the brain’s reward system by flooding the circuit with dopamine.  Dopamine is a neurotransmitter that controls movement, emotion, motivation, and feelings of pleasure.  An over-stimulation of this system produces euphoric effects in response to the drug.  The users’ reaction to this teaches them to repeat the behavior of abusing the drug.  The brain adapts to the overwhelming surges in dopamine and begins to produce less and reduces the number of dopamine receptors in the reward circuit.  This process reduces the abuser’s ability to enjoy the drug and then builds up a tolerance for future uses.  Research has also shown long-term causes in other brain chemical systems and circuits.  Glutamate is a neurotransmitter that influences the reward circuit and the ability to learn.  When glutamate is altered by marijuana, the brain begins to impair cognitive functions.  Brain imaging studies have proven that drug-addicting individuals show changes in areas of the brain that are critical to judgment, decision making, learning and memory, and behavior control (What Happens).

In Jennifer Warner’s article, she states “the effects of marijuana in the brain may linger long after the last joint goes out.”  No one really thinks about the aftermath of smoking marijuana.  They get that high and that is all that matters.  This article explains a study shows how blood flow to the brain in people who smoked marijuana remain altered up to a month after they last smoked.  Researchers studied the blood flow in brain arteries of 54 marijuana users and 18 nonusers.  The participants, who normally smoke, volunteered to abstain from marijuana use for a month.  The blood flow was analyzed at the beginning of the study and at the end of the month for marijuana users.  At the beginning and end of the study, researchers found that blood flow was significantly higher in marijuana users than in nonusers (Warner).

In conclusion, marijuana can be a very dangerous drug to the nervous system.  A lot of people do not see much harm in this drug; they almost see it as the “safe drug”.  However, there are several immediate causes and long-term causes that can arise from smoking marijuana that people need acknowledge.  The biggest takeaways people need to be aware of is what the drug really is, its street names, how long it can stay in your body and how it affects the most important system in your body, central nervous system. Marijuana is a very common and widely used drug, that does not mean it is safe and something that is accepted in our society as a recreational drug.   

Works Cited

Bora, Chandramita. “Effects of Marijuana on the Brain.” Intelligent Life on the Web. 2009. Web. 16 Nov. 2010. < marijuana-on-the-brain.html >.

Chudler, Eric. “Marijuana.” Neuroscience for Kids. 2008. Web. 16 Nov. 2010. < >.

Ejelonu, Akudo. “How Does Marijuana Affect the Brain?” Serendip. 10 Jan. 2008. Web. 16 Nov. 2010. < >.

Gruber, Staci A. “Altered Affective Response in Marijuana Smokers: An FMRI Study.” 105, Issues 1-2. (2009): 139-153. SciVerse. Web. 16 Nov. 2010. “Marijuana: Facts for Teens.” National Institute on Drug Abuse. March 2008. Web. 16 Nov. 2010. < >.

Warner, Jennifer. “Marijuana’s Effects Linger in the Brain.” Web MD Health News. 7 Feb. 2005. Web. 16 Nov. 2010. < >.

“What Happens to your Brain When you Smoke Marijuana?”  Official KM Lida Wholesale. 2007-2010. Web. 16 Nov 2010.  

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  1. Jared, 2 years ago Reply

    Yes I believe marijuana is overused to cover up hidden issues, for example I used to self medicate with marijuana as it helped with my Restless Leg Syndrome (RLS) however when I was self medicating, I didn’t know I had RLS, I just knew I struggled falling asleep at night and weed helped. Once I found out I had RLS, I started doing research to treat it and I ended up not needing to self medicate anymore since I started using L-Theatine which blocks glutamate, which gets overproduced with RLS. Just my 2 cents.

  2. Derek D, 1 year ago Reply

    Cannabis reduces glutamate in brain. Excessive glutamate linked to challenging autistic behaviors. Thus, cannabis can be beneficial to people with autism.

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