Ana Radovic
MPHP 439
Marijuana:
Epidemiology:
Use and Demographic Trends
Marijuana
is the most consumed illegal substance in the
Youth
American
youth in the ‘70’s used marijuana in high numbers, up to 60% of 12th
graders in 1979 had tried the drug. In
1992, that number fell to 33% and then rose again to 50% in 1997 (23). These rates have leveled off and currently,
according to the 2004
Adults
In 2003, the National
Survey on Drug Use and Health (NSDUH) showed that more than 40% of Americans
age 12 and older had tried using marijuana (23). During a 1999 meeting of the Community
Epidemiology Work Group which tracks effects of drug abuse in different
the previous year, 5% had smoked
in the previous month, and less than 5% were using every week (7).
Demographics
Rates of marijuana use
vary between different races and genders, and not only in different age
groups. Among adolescents, male and
Hispanic students showed higher rates of drug use on school grounds, than
female and white students (9). Different
countries show different rates of use as well.
In a study of 31 countries, lifetime cannabis use was highest in
Marijuana
as a Substance
RISKS AS PERTAINS TO ABUSE
Lung
Effect
Studies show that
individuals involved in chronic marijuana use show the same kinds of
respiratory symptoms as tobacco smokers.
These include coughing, wheezing, and bronchitis (38). Smoking tobacco at the same time therefore
may have even increased risks for lung problems, but another downside is that
marijuana has been shown to make quitting tobacco more challenging (10). One study showed that employees who smoke
marijuana miss more days of work and report increased health problems, mostly
due to respiratory illnesses (23).
Cancer
Just as marijuana shows similar
respiratory changes as tobacco, it also shows similar cellular changes in the
bronchial tract which are pre-cancerous (138).
These similar changes are for regular marijuana use and regular tobacco
use. Regular marijuana use is defined as
a smaller amount smoked than regular tobacco use, which implies that marijuana
is in fact more damaging to the respiratory tract than tobacco (34). Also, the carcinogenic hydrocarbons found in
marijuana smoke are 50 to 70% greater than in tobacco smoke (23). These changes increase the tendency to
develop lung cancer, and imply that marijuana may pose as a similar or greater
risk factor than tobacco although more epidemiological evidence is needed.
Marijuana
has been shown to increase cancer of the head and neck in some studies. Dr. Daniel Ford of
Studies
also show that marijuana may increase the risk of transitional cell carcinoma,
a cancer found mostly in the bladder (6).
This was seen for men aged less than 60 years.
Cognitive
Effects
Marijuana use is often
associated with memory loss and learning disabilities. Various studies have been done to prove or
disprove this correlation. Differences occur
between effects of acute marijuana use and chronic long-term use on cognition.
Studies
on acute effects show that what is most likely affected is distance and time
perception (time seems to lengthen and distance seems to increase between
objects), vision (more difficult to discriminate colors), complex reaction
time, recognition memory,
and recall (7). In summary, simple tasks are not affected but
more complex tasks, especially those requiring rapid thinking are.
Rats that
are exposed to THC, the active ingredient in marijuana, have less of an ability
to use short-term memory. These same
effects are seen in rats that have a part of their brain destroyed in the
hippocampal region which is involved in short-term memory (23).
Studies
on chronic use showed less gross effects on neuropsychological impairments such
as those seen with alcohol abuse, but some highly sensitive tests show
difficulty in transferring information from short-term memory to long-term
memory (7). A very well-controlled study
showed differences in brain waves in chronic marijuana users when performing
difficult tasks. These users could not
process information as rapidly (31).
Other
studies demonstrate learning deficits in heavy users of marijuana, but often
these cognitive abilities can be regained after abstinence (26). A meta-analysis showed that long-term use was
not associated with generalized neurocognitive decline except for a small
decline in the capability of learning new information (12).
There
are important differences seen in the adolescent age group in terms of
cognition. One study showed that adults
who began smoking marijuana before age 17 had smaller brains, a lower percentage
of gray matter – which is the substance of the brain, and a higher percentage of
white matter – which is the conducting system of the brain, than adults who had
not (36). Another study showed that
someone who begins smoking at age 13 will earn less money and will have
completed less education as a young adult (8).
This could possibly be associated with deficits in cognition. Marijuana use may impact brain development in
a critical period, and that suggests that adolescents using marijuana should
have more targeted precautions for use.
Immune
System
Mice exposed to THC were
shown to have an impairment of immune function which reduced their ability to
slow tumor growth and fight infections (27).
More research is needed to determine whether marijuana reduces the same
capabilities in humans.
Heart
Attack/Stroke
Acute
effects of marijuana include an increase in heart rate and blood pressure. One study shows that the risk of heart attack
immediately after smoking marijuana is four times greater. This is especially significant for older
individuals who have an increased risk
of a cardiovascular event such as
heart attack or stroke due to age. A
review of studies on
cardiovascular risks of cannabis
showed that in fact the cardiac effects of marijuana do not pose a risk for
young otherwise healthy individuals, but do for older people (19).
Risks
with pregnancy
There are specific risks
which have been associated with marijuana use during pregnancy. Neonates of women using marijuana develop
certain characteristics which reflect possible problems in neurological
development. Young children grow to more
often experience symptoms of inattention and impulsivity associated with
Attention Deficit Hyperactivity Disorder (ADHD), and also some deficits in
learning and memory (18).
Marijuana
has also been shown to decrease fertility in men by decreasing the
effectiveness of sperm in fertilizing an egg (29).
Emergency
Department/Accidents
In
2000, Iversen reported that there had been no deaths from THC overdose. Animal studies show that an extremely high
and improbable amount of joints would need to be smoked in order to achieve
toxic levels. Nonetheless, marijuana is
still a somewhat frequent factor involved in emergency visits. In 2002, marijuana was a contributing factor
in 15% of ED visits in 12–17 year olds for unspecified causes (33). Certain studies show that 6-11% of fatal
accident victims test positive for THC but they often test positive for alcohol
as well.
Driving
The National Highway
Traffic Safety Administration advises against driving while under the influence
of marijuana. A study they conducted
showed that marijuana impaired driving performance, but especially when
combined with alcohol, showing a greater effect than alcohol alone (25). On the other hand, lab studies show that
marijuana users compensate for driving inadequacies by driving slower and
keeping a greater distance between cars so that they are less likely to cause
an accident and epidemiological studies confirm this (1). This compensation though may not be
sufficient when rapid thinking is needed in a driving situation, and as described
in the section on cognition, rapid thinking is impaired under acute
intoxication.
MENTAL HEALTH/SOCIAL HEALTH
Mental
Health Damage
Marijuana abuse has
frequently been associated with depressive and even psychotic symptoms but it
is often unclear as to whether these mental health disorders are caused by
marijuana, self-medicated by marijuana, or are explained by outside
factors. Marijuana intoxication can
produce behaviors that are schizophrenic in nature, but these behaviors go away
after acute use (14). One review claims
that studies do point to an association between psychosis and marijuana use and
proposes a biological explanation, referencing studies which show increases in
psychosis not explained by other factors (13).
Another explanation may be that people with mental illnesses self-medicate
with marijuana. A New Zealand study
showed that people with mental illness are 15 times more likely to use
marijuana at age 18 (7).
Other
studies show associations with depressive symptoms, defined by a certain
amotivational syndrome, where individuals do not achieve the same educational
and behavior goals as others with similar characteristics. Research shows that there are not differences
in school performance in college students who use and don’t use marijuana (38),
but that high school students who use marijuana have lower grades, quit school
more often, and spend less time on homework (20). A causal relationship is refuted by a study
that shows poor school performance prior to initiating marijuana use (30). There may be a reason explaining both poor
school performance and increased marijuana use and this reason could possibly
be increased deviant behavior. These
individuals may have oppositional defiant disorder, associated with breaking
the rules. Because marijuana is illegal
and easily accessed, it may just represent another rule that can be broken.
A
job-related study supports amotivational syndrome. Workers who smoke marijuana have a 75%
increase in absenteeism. Also of note is
a 55% increase in industrial accidents and 85% increase in injuries on the job (23).
When
controlling for income and family of origin, one study found that marijuana
users were less likely to complete college and were more likely to have an
income of less than $30,000 than their peers.
Another
correlation with depressive symptoms is demonstrated by a study which showed
that people who smoke marijuana before the age of 17 are 3.5 more likely to
attempt suicide as those who start later.
Also, the same study showed that marijuana dependent individuals have a
higher prevalence of major depressive disorder (22). As stated before for psychotic symptoms, the
causal relationship is unclear.
Withdrawal/Dependence
Sometimes marijuana use
can lead to dependence and problems with addiction. Dependence according to the DSM-IV, the
diagnostic manual of psychiatrists, dependence requires 3 of 7 symptoms in the
same year. These symptoms include
tolerance, withdrawal, using more than intended, being unable to cut down,
increasing the time spent using, giving up other life activities, and using
despite consequences. The 2003 National
Drug Use and Health (NSDUH) study reports that 4.2 million Americans are
dependent or abusing marijuana (23). Of
42,000 people surveyed in a 1998 study, 23% were diagnosed with abuse and 6% were
diagnosed with dependence.
Marijuana smokers do experience withdrawal
symptoms, although often these are not as physical as those for other illicit
drugs such as cocaine and heroin. These
withdrawal symptoms include irritability, a depressed mood, lack of appetite,
cravings, anger, and restlessness. These
symptoms can be as severe as tobacco withdrawal (4).
Violence/Aggression
People
sometimes associate marijuana with aggressive behavior. In fact, laboratory test show that an
increased THC level does not increase competitive behavior in test subjects (24),
although sometimes withdrawal symptoms may include aggression (21). The 2002 National Institute of Justice’s
Arrestee Drug Abuse Monitoring Program found that of arrested individuals, 41%
of males and 27% of females were found to test positive for marijuana (7). This may not point to a causal relationship
since many of the same people tested positive for other illicit drugs or
alcohol. A NIDA Research summary
provides evidence which supports that often marijuana is combined with other
illicit drugs, and this may contribute to the aggressive behavior.
GATEWAY
A
highly debatable topic is whether or not marijuana is a gateway drug, or a drug
which once initiated, leads to the use of other drugs, which are often more
harmful and addictive. Data from the
Substance Abuse and Mental health Services Administration in 2000 showed that
of those who have tried marijuana, 77% have tried crack, 33% have tried
cocaine, and 3.9% have tried heroin.
Although most users of hard drugs try marijuana first, most of marijuana
users do not try hard drugs (7). There
are different explanations for why these associations exist. One is that users of marijuana, by virtue of
marijuana being an
illegal drug, will also be
exposed to a market of other illegal drugs, which is less likely for someone
who abuses alcohol or tobacco, which are legal.
Another explanation is that some marijuana users exhibit deviant
behavior which motivates them to abuse illegal substances and therefore
influences the use of both marijuana and other illicit drugs. Another theory is that there may be
pharmacological effects associated with marijuana use which increase the
likelihood of use of other illicit drugs.
An experiment performed in 1997 demonstrated that rats exposed to THC
did not show a greater propensity to push levers for other drugs (28). On the other hand, a dose-response
relationship was found by researchers correlating the amount of marijuana use
at age 16 with alcohol and other substance use by age 18 (13). One paper suggests that animal studies which
show similar neurological effects of cannabis and cocaine and heroin suggest
that use of one may influence the use of another (13).
TREATMENT/PREVENTION
Treatment
Techniques
Project
MATCH, a 1998 comparative study of cognitive behavioral therapy, 12-step
facilitation, and motivational interviewing showed that all three treatment
approaches showed comparable effectiveness in treating marijuana addiction. The author of the study cited previously on
effects of withdrawal suggests that marijuana abusers trying to quit should be
informed of what to expect in terms of withdrawal symptoms in order to
normalize the process and treat some of the symptoms involved in order to decrease
the likelihood of relapse (4). Another
author previously cited when discussing increased rates of suicide and
depressive symptoms associated with marijuana use, argues that although a
causal relationship is unclear, what is clear is the likelihood for other
mental disorders in a marijuana abuser and it is important for those to be
addressed at the same time as the addictive symptoms (22).
One
possible treatment option that is not available yet is medication. Some illegal drug use is able to be medicated
by drugs which conflict with the actions of the illicit drug and therefore
either reduce the response, or produce an undesired response in order to reduce
the desire to use the illicit drug. One
drug currently being studied called SR141716 shows the same effects for
marijuana, and blocks the receptors which marijuana binds to in humans (17). This development poses new options for
abusers of marijuana who require treatment.
Treatment
Programs
Some
research shows that outpatient interventions associated with social support
show some of the best improvements in marijuana addiction (7). Other research demonstrates the effectiveness
of voucher programs, where individuals are compensated with gifts for
abstaining from drug use (3). In 2001,
an evaluation of 23 community-based adolescent treatment programs found a
decrease from 80% to 44% of weekly marijuana use, fewer thoughts of suicide,
higher self-esteem, and better school performance (16).
Prevention
The aforementioned risk of
marijuana use specifically associated with adolescents emphasizes the need for
preventive efforts against early use and any time abuse of marijuana. Educational programs such as the well-known
police enforced DARE program have been shown to be ineffective. The best preventive methods employ social
influence such as changing social norms so that individuals understand the
reality of the drug environment and that not “everyone is doing it”, teaching
drug refusal skills, and using cognitive behavioral skills to make decisions
based on pros and cons (7). In rural
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