Marijuana

Marijuana is one of the world's most commonly used illegal drugs. There are approximately 300 million users worldwide and 28 million users in the United States (Diaz, 1997). Marijuana comes from a plant called "Cannabis sativa." The chemical in this plant that produces the altered states of consciousness is called "delta-9 tetrahydrocannabinol" or "THC." Marijuana is usually smoked like a cigarette, but it can also be cooked into baked goods like brownies or cookies or brewed like a tea. THC is also contained in "hashish" (hash) which is the resin from the marijuana plants. Hash is usually smoked in a pipe. Other names for marijuana include: grass, pot, reefer and weed.

Effects of Marijuana on the Nervous System THC acts on "cannabinoid" receptors which are found on neurons in many places in the brain. These brain areas are involved in memory (the hippocampus), concentration (cerebral cortex), perception (sensory portions of the cerebral cortex) and movement (the cerebellum, substantia nigra, globus pallidus). When THC activates cannabinoid receptors, it interfers with the normal functioning of these brain areas. In low to medium doses, marijuana causes: relaxation reduced coordination reduced blood pressure sleepiness disruption in attention an altered sense of time and space...a good reason not to drive or operate machinery while under the influence. In high doses, marijuana can cause: hallucinations delusions impaired memory disorientation. Scientists have known for a long time that THC interacted with cannabinoid receptors in the brain, but did not know why the brain would have such receptors. They thought that the brain must make some kind of substance that naturally acted on these receptors. In 1992, they found the answer...anandamide. Anandamide is the brain's own THC (just like "endorphin" is the brain's own morphine). Still, scientists are not sure what the function of anandamide is in the normal brain. The effects of marijuana start as soon as 1-10 minutes after it is taken and can last 3 to 4 hours or even longer. Experiments have shown that THC can affect two neurotransmitters: norepinephrine and dopamine. Serotonin and GABA levels may also be altered.

Whether marijuana can produce addiction is controversial. Also controversial is whether marijuana causes long-term mental abnormalities. Only future research will give us the answers. It is interesting to note that there are NO documented cases of a fatal overdose produced by marijuana. However, because there is a high level of tar and other chemicals in marijuana, smoking it is similar to smoking cigarettes. The lungs get a big dose of chemicals that increase the chances of lung problems and cancer later in life.

In 1969, the Journal of the American Medical Association (JAMA, vol. 207, pages 1349-1350, 1969) published a paper that described the psychoactive effects of catnip in people. People who smoked catnip were said to become happy and relaxed. Catnip (from the plant Nepeta cataria) DOES cause most cats to act strangely: they roll around, shake their heads, rub against things, and try to get the plant all over their bodies. Interestingly, cats are only affected when they smell it - it has NO EFFECT if they eat it. It appears that catnip has little or no psychoactive effects in people. Actually, in the 1969 JAMA paper, the authors mislabeled the pictures of marijuana and catnip. They labeled the pictures of marijuana as catnip and that of catnip as marijuana.

Hear It

"Anandamide"

"Cannabinoid"

Take a short on-line, interactive quiz about amphetamines, cocaine and marijuana.

Did you know?

Marijuana contains more than 400 different chemicals.

For more information about marijuana, see: Diaz, J. How Drugs Influence Behavior. A Neuro-Behavioral Approach, Upper Saddle River (NJ): Prentice Hall, 1997. Marijuana: Facts for Teens - from the National Institute on Drug Abuse Marijuana: Facts for Parents - from the National Institute on Drug Abuse Marijuana Facts for Parents - from the National Institute on Drug Abuse Marijuana Special Report - from New Scientist Marijuana Update from the National Institute on Drug Abuse. What's Your Poison - Marijuana

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