| 
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, it has appeared in blunts. These are
cigars that have been emptied of tobacco and re-filled
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 nonidentical
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 would
be different even for identical twins 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 acted on by the hippocampus. This 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 are suppressed
by THC. In addition, researchers have discovered that learned
behaviors, which depend on the hippocampus, also deteriorate.
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 that tobacco smokers have. 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.
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 significantly increase risks
of overload on the cardiovascular system.
Effects
of Heavy Marijuana Use on Learning and Social Behavior
A
study of college students has shown that critical skills
related to attention, memory, and learning are impaired
among people who use marijuana heavily, even after discontinuing
its use for at least 24 hours. Researchers compared 65 "heavy
users," who had smoked marijuana a median of 29 of the past
30 days, and 64 "light users," who had smoked a median of
1 of the past 30 days. After a closely monitored 19- to
24-hour period of abstinence from marijuana and other illicit
drugs and alcohol, the undergraduates were given several
standard tests measuring aspects of attention, memory, and
learning. Compared to the light users, heavy marijuana users
made more errors and had more difficulty sustaining attention,
shifting attention to meet the demands of changes in the
environment, and in registering, processing, and using information.
The findings suggest that the greater impairment among heavy
users is likely due to an alteration of brain activity produced
by marijuana.
Longitudinal
research on marijuana use among young people below college
age indicates those who used have lower achievement than
the non-users, more acceptance of deviant behavior, more
delinquent behavior and aggression, greater rebelliousness,
poorer relationships with parents, and more associations
with delinquent and drug-using friends.
Research
also shows more anger and more regressive behavior (thumb
sucking, temper tantrums) in toddlers whose parents use
marijuana than among the toddlers of non-using parents.
Effects
on Pregnancy
Any
drug of abuse can affect a mother's health during pregnancy,
and this is a time when she should take special care of
herself. Drugs of abuse may interfere with proper nutrition
and rest, which can affect good functioning of the immune
system. Some studies have found that babies born to mothers
who used marijuana during pregnancy were smaller than those
born to mothers who did not use the drug. In general, smaller
babies are more likely to develop health problems.
A
nursing mother who uses marijuana passes some of the THC
to the baby in her breast milk. Research indicates that
the use of marijuana by a mother during the first month
of breast-feeding can impair the infant's motor development
(control of muscle movement).
Addictive
Potential
A
drug is addicting if it causes compulsive, often uncontrollable
drug craving, seeking, and use, even in the face of negative
health and social consequences. Marijuana meets this criterion.
More than 120,000 people seek treatment per year for their
primary marijuana addiction. In addition, animal studies
suggest marijuana causes physical dependence, and some people
report withdrawal symptoms.
Extent
of Use
Marijuana Use by ages 14 years
and over, 1991-2001:
National Drug Strategy Household Survey
| |
1991 |
1993 |
1995 |
1998 |
2001 |
| Ever
Used |
32.5 |
34.7 |
31.0 |
39.1 |
33.1 |
| Used
in Past Year |
--- |
--- |
--- |
17.9 |
12.9 |
| Used
in Past Month |
--- |
--- |
--- |
--- |
7.8 |
| Daily
Use in Past Month |
--- |
--- |
--- |
--- |
16.0 |
Information
on this page courtesy of National Institute on Drug Abuse.
|
