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Marijuana is a green or gray mixture of dried, shredded flowers and leaves of the hemp
plant Cannabis sativa. There are over 200 slang terms for marijuana including "pot,"
"herb," "weed," "boom," "Mary Jane," "gangster," and "chronic." It is usually smoked as a
cigarette (called a joint or a nail) or in a pipe or bong. In recent years, marijuana has
appeared in blunts, which are cigars that have been emptied of tobacco and refilled with
marijuana, often in combination with another drug, such as crack. Some users also mix
marijuana into foods or use it to brew tea.

The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol). In 1988, it
was discovered that the membranes of certain nerve cells contain protein receptors that
bind 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. The short
term effects of marijuana use include problems with memory and learning; distorted
perception; difficulty in thinking and problem-solving; loss of coordination; and
increased heart rate, anxiety, and panic attacks.

Scientists have found that whether an individual has positive or negative sensations after
smoking marijuana can be influenced by heredity. A recent study demonstrated that
identical male twins were more likely than non-identical male twins to report similar
responses to marijuana use, indicating a genetic basis for their sensations. Identical
twins share all of their genes, and fraternal twins share about half.

Environmental factors such as the availability of marijuana, expectations about how the
drug would affect them, the influence of friends and social contacts, and other factors
that differentiate identical twins' experiences also were found to have an important
effect; however, it also was discovered that the twins' shared or family environment
before age 18 had no detectable influence on their response to marijuana.

Health Hazards
Effects of Marijuana on the Brain
Researchers have found that THC changes the way in which sensory information gets into and
is processed by the hippocampus. The hippocampus is a component of the brain's limbic
system that is crucial for learning, memory, and the integration of sensory experiences
with emotions and motivations. Investigations have shown that neurons in the information
processing system of the hippocampus and the activity of the nerve fibers in this region
are suppressed by THC. In addition, researchers have discovered that learned behaviors,
which depend on the hippocampus, also deteriorate via this mechanism.

Recent research findings also indicate that long-term use of marijuana produces changes in
the brain similar to those seen after long-term use of other major drugs of abuse.

Effects on the Lungs
Someone who smokes marijuana regularly may have many of the same respiratory problems as
tobacco smokers. These individuals may have daily cough and phlegm, symptoms of chronic
bronchitis, and more frequent chest colds. Continuing to smoke marijuana can lead to
abnormal functioning of lung tissue injured or destroyed by marijuana smoke.

Regardless of the THC content, the amount of tar inhaled by marijuana smokers and the
level of carbon monoxide absorbed are three to five times greater than among tobacco
smokers. This may be due to the marijuana users' inhaling more deeply and holding the
smoke in the lungs and because marijuana smoke is unfiltered.

Effects on Heart Rate and Blood Pressure
Recent findings indicate that smoking marijuana while shooting up cocaine has the
potential to cause severe increases in heart rate and blood pressure. In one study,
experienced marijuana and cocaine users were given marijuana alone, cocaine alone, and
then a combination of both. Each drug alone produced cardiovascular effects; when they
were combined, the effects were greater and lasted longer. The heart rate of the subjects
in the study increased 29 beats per minute with marijuana alone and 32 beats per minute
with cocaine alone. When the drugs were given together, the heart rate increased by 49
beats per minute, and the increased rate persisted for a longer time. The drugs were given
with the subjects sitting quietly. In normal circumstances, an individual may smoke
marijuana and inject cocaine and then do something physically stressful that may
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