Mary J

Marijuana is the most commonly abused illicit drug in the United States.

A dry, shredded green/brown mix of flowers, stems, seeds, and leaves of the

hemp plant Cannabis sativa, it usually is smoked as a cigarette (joint, nail), or in

a pipe (bong). It also is smoked in blunts, which are cigars that have been

emptied of tobacco and refilled with marijuana, often in combination with

another drug. It might also be mixed in food or brewed as a tea. As a more

concentrated, resinous form it is called hashish and, as a sticky black liquid, hash

oil. Marijuana smoke has a pungent and distinctive, usually sweet-and-sour

odor. There are countless street terms for marijuana including pot, herb, weed,

grass, widow, ganja, and hash, as well as terms derived from trademarked

varieties of cannabis, such as Bubble Gum, Northern Lights, Fruity Juice, Afghani

#1, and a number of Skunk varieties.

The main active chemical in marijuana is THC

(delta-9-tetrahydrocannabinol). The membranes of certain nerve cells in the brain

contain protein receptors that bind to THC. Once securely in place, THC kicks off

a series of cellular reactions that ultimately lead to the high that users experience

when they smoke marijuana

Scientists have learned a great deal about how THC acts in the brain to

produce its many effects. When someone smokes marijuana, THC rapidly passes

from the lungs into the bloodstream, which carries the chemical to organs

throughout the body, including the brain.

In the brain, THC connects to specific sites called cannabinoid receptors

on nerve cells and influences the activity of those cells. Some brain areas have

many cannabinoid receptors; others have few or none. Many cannabinoid

receptors are found in the parts of the brain that influence pleasure, memory,

thought, concentration, sensory and time perception, and coordinated

movement.

The short-term effects of marijuana can include problems with memory

and learning; distorted perception; difficulty in thinking and problem solving;

loss of coordination; and increased heart rate. Research findings for long-term

marijuana abuse indicate some changes in the brain similar to those seen after

long-term abuse of other major drugs. For example, cannabinoid (THC or

synthetic forms of THC) withdrawal in chronically exposed animals leads to an

increase in the activation of the stress-response system and changes in the

activity of nerve cells containing dopamine. Dopamine neurons are involved in

the regulation of motivation and reward, and are directly or indirectly affected

by all drugs of abuse.

A study of 450 individuals found that people who smoke marijuana

frequently but do not smoke tobacco have more health problems and miss more

days of work than nonsmokers. Many of the extra sick days among the

marijuana smokers in the study were for respiratory illnesses.

Even infrequent abuse can cause burning and stinging of the mouth and

throat, often accompanied by a heavy cough. Someone who smokes marijuana

regularly may have many of the same respiratory problems that tobacco smokers

do, such as daily cough and phlegm production, more frequent acute chest

illness, a heightened risk of lung infections, and a greater tendency to obstructed

airways. Smoking marijuana possibly increases the likelihood of developing