Marijuana
Use and Health
Marijuana is the most commonly abused illicit
drug in the United States. It is a dry, shredded green
and brown mix of flowers, stems, seeds, and leaves derived
from the hemp plant Cannabis sativa. The main active
chemical in marijuana is delta-9-tetrahydrocannabinol;
THC for short.
How Does Marijuana Affect the Brain?
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
the brain and other organs throughout the body.
THC acts upon specific sites in the brain, called cannabinoid
receptors, kicking off a series of cellular reactions
that ultimately lead to the “high” that
users experience when they smoke marijuana. Some brain
areas have many cannabinoid receptors; others have few
or none. The highest density of cannabinoid receptors
are found in parts of the brain that influence pleasure,
memory, thoughts, concentration, sensory and time perception,
and coordinated movement.
Not surprisingly, marijuana intoxication can cause distorted
perceptions, impaired coordination, difficulty in thinking
and problem solving, and problems with learning and
memory. Research has shown that marijuana’s adverse
impact on learning and memory can last for days or weeks
after the acute effects of the drug wear off.2 As a
result, someone who smokes marijuana every day may be
functioning at a suboptimal intellectual level all of
the time.
Research on the long-term effects of marijuana abuse
indicates some changes in the brain similar to those
seen after long-term abuse of other major drugs. For
example, cannabinoid withdrawal in chronically exposed
animals leads to an increase in the activation of the
stress-response system3 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.
Effects on the Heart
Marijuana increases heart rate by 20–100 percent
shortly after smoking; this effect can last up to 3
hours. In one study, it was estimated that marijuana
users have a 4.8-fold increase in the risk of heart
attack in the first hour after smoking the drug.
Effects on the Lungs
Numerous studies have shown marijuana smoke to contain
carcinogens and to be an irritant to the lungs. In fact,
marijuana smoke contains 50-70 percent more carcinogenic
hydrocarbons than does tobacco smoke.
Material above is courtesy of: http://www.cdc.gov
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