Marijuana - Effects on the Body

Effects on the Body

The human brain contains receptorsGroup of cells that receive stimuli., specifically for cannabinoids. The brain also produces its own natural cannabinoids, called anandamide (uh-NANN-duh-myd) and 2-arachidonylglycerol (AH-ruh-kid-ON-uhl-GLISS-uh-rol). These two compounds have been found in the brains of animals as well.

The most common way of using marijuana is to smoke it. Some users roll small amounts of the drug into cigarette papers. These marijuana cigarettes are called spliffs or joints. Photo by Jim Pozarik/Getty Images.
The most common way of using marijuana is to smoke it. Some users roll small amounts of the drug into cigarette papers. These marijuana cigarettes are called spliffs or joints. Photo by Jim Pozarik/Getty Images.

What Happens in the Brain

All of the cannabinoid receptors are located in the brain. There are no cannabinoid receptors in the spinal column, so using marijuana does not affect a person's ability to breathe or the function of other organs in the body.

When marijuana is smoked, THC and the other cannabinoids flow to the brain from the lungs, where the compounds are transferred into the bloodstream. The effects begin within minutes, generally with a feeling of light-headedness and euphoria (intense happiness). The user may become less inhibited, more outgoing, and laugh easily. At the same time, the user can experience a loss of motor control and difficulty concentrating. Since most of the cannabinoid receptors are located in the hippocampusA part of the brain that is involved in learning and memory., the center of memory and learning, people high on marijuana have difficulty learning new things or remembering what is happening at the moment. Marijuana does not destroy memories that already exist before the user gets high.

The typical marijuana experience is one of euphoria, heightened sensations of music and light, relaxation, and increased appetite. Sometimes, however, even the most experienced users will react differently. The drug can heighten anxiety and create paranoiaAbnormal feelings of suspicion and fear.—an uncomfortable feeling of danger or distress. When that happens, the user can do little but ride out the unpleasant experience, which usually happens within two to three hours.

The marijuana high gradually changes to a period of diminished physical activity and communication. The term "stoned" was coined to describe this period. In two to six hours the cannabinoid overload begins to exit the brain, usually causing a spike in appetite along the way. When users get hungry, they are said to have "the munchies."

It is not possible to smoke a fatal dose of marijuana. It is possible to consume too much THC by eating baked goods with hashish in them. Still this does not lead to death, but rather to a possibly unpleasant "trip" with paranoid or psychotic (extremely frightening) episodes. Again, no antidote to cannabis exists except trying to get the victim to vomit the undigested portion of the baked goods.

Effects on Judgment, Memory, and Learning

There is no such thing as a safe recreational drug. A person high on marijuana has the same lack of judgment, poor coordination, and diminished sense of fear as a person drunk on whiskey. The leading cause of death for young people is automobile crashes—and sometimes those fatal crashes are caused by marijuana, or a combination of marijuana and other drugs or alcohol. Marijuana impairs the ability to drive, operate machinery, or judge dangerous situations. As such, it can be deadly.

Because marijuana affects memory and learning, daily use can undermine a student's ability in school or a worker's capability on the job. Although scientists have debunked the old caution that marijuana affects motivation, the drug does affect short-term memory and the brain's ability to process new material. People who smoke marijuana regularly almost always experience declines in grades and difficulties in the classroom related to the drug use.

THC, the most active component of marijuana, remains in the body long after the psychoactive effects have worn off. The body stores THC in its fat cells. After one use, a person will test positive for THC for as many as three days. With regular use, a person can test positive for THC even after abstaining from marijuana for four weeks. The drug tests available at the turn of the twenty-first century were sophisticated enough that they do not yield a positive result for "passive" marijuana smoking (just being around other people who

In late 2004 Australian police began stopping motorists randomly to conduct saliva tests. The test checks salivia for various illegal drugs, including marijuana and amphetamines. Photograph by Trevor Pinder/Newspix/Getty Images.
In late 2004 Australian police began stopping motorists randomly to conduct saliva tests. The test checks salivia for various illegal drugs, including marijuana and amphetamines. Photograph by Trevor Pinder/Newspix/Getty Images.

are using the drug). Thus, law enforcement officers will not accept that as a defense. As Paul M. Gahlinger stated in his book, "If the drug test is positive for marijuana, the only legitimate excuse is either the use of dronabinol or, if allowed, the use of medically prescribed marijuana."

What Happens in the Lungs

Marijuana smoke contains the same cancer-causing compounds as tobacco, including tar, benzanthrene (ben-ZANN-threen), and benzpyrene (benz-PIE-reen). Since marijuana smokers inhale more deeply—and because joints, pipes, and blunts do not contain filters—the user exposes the lungs to more of the cancer-causing agents. Smoking marijuana daily or even occasionally for a period of years increases the risk of lung cancer. Smoking both marijuana and tobacco greatly increases that risk.

Link to Mental Illness?

A study released in 2005 by the Office of National Drug Control Policy found that people who begin smoking marijuana at a young age—between ten and fourteen—run a high risk of mental problems later in life. The study found that between 8 and 9 percent of the general population develop serious mental illnesses in adulthood. For people who begin using marijuana before the age of twelve, the chances of developing mental illness leap to 21 percent. Two reasons could account for this. First, marijuana could have a bad effect on the developing brain. Second, someone tempted to use marijuana at such a young age might already be predisposed to have emotional or psychological problems. Also, a significant percentage of heavy marijuana users may be "self-medicating" to treat a variety of mental conditions. These conditions include anxiety, phobias, or depression.

Withdrawal from marijuana is not terribly difficult, even after heavy use. The symptoms of marijuana withdrawal include insomnia, anxiety, decreased appetite, and irritability. Usually these symptoms go away within a few weeks if the user does not return to the drug.

A "Gateway Drug"?

For several decades marijuana has been described as a "gateway drug"—one that leads users to experiment with more dangerous, more addictive substances. That theory has been dismissed, however. Most people use marijuana and then stop taking any illegal drugs. Far fewer progress to other substances. So it could just as easily be said that marijuana is an "end stage" drug. Again, the individual person's mental makeup determines whether or not marijuana use will lead to harder drugs. People with family histories of mental problems, alcoholism, anxiety, or depression should try to avoid every psychoactive substance, including legal ones like alcohol and nicotine. (Entries for alcohol and nicotine are available in this encyclopedia.) For anxious or depressed people, better treatments exist than marijuana use.