MEMORY/PERCEPTION/BEHAVIOR
1. Attention, memory and learning are impaired among heavy
marijuana users, even after users discontinued its use for at least
24 hours. Heavy marijuana use is associated with residual
neuropsychological effects even after a day of supervised abstinence
from the drug. Heavy users displayed significantly greater
impairment than light users on attention/executive functions, as
evidenced particularly by greater preservations on card sorting and
reduced learning of word lists. These differences remained after
controlling for potential confounding variables, such as estimated
levels of premorbid cognitive functioning, and for use of alcohol
and other substances in the two groups. However, the question
remains open as to whether this impairment is due to a residue of
drug in the brain, a withdrawal effect from the drug, or a frank
neurotoxic effect of the drug. ("The Residual Cognitive Effects
of Heavy Marijuana Use in College Students," Pope, HG Jr.,
Yurgelun-Todd, D., Biological Psychiatry Laboratory, McLean
Hospital, Belmont, MA, JAMA February 21, 1996.)
2. Impaired memory for recent events, difficulty concentrating,
dreamlike states, impaired motor coordination, impaired driving and
other psychomotor skills, slowed reaction time, impaired
goal-directed mental activity, and altered peripheral vision are
common associated effects. (Adams and Martin 1996; Fehr and Kalant
1983; Hollister 1988a; Institute of Medicine 1982; Tart 1971)
3. A roadside study of reckless drivers who were not impaired by
alcohol, showed that 45% of these drivers tested positive for
marijuana. (Dr. Dan Brookoff, published in the New England Journal
of Medicine)
4. Marijuana smoking affects the brain and leads to impaired
short-term memory, perception, judgment and motor skills. (Marijuana
Facts: Parents Need to Know, National Institute on Drug Abuse )
5. In a survey of 150 marijuana using students, 59% surveyed
report they sometimes forget what a conversation is about before it
has ended. 41% report if they read while stoned they remembered less
of what they had read hours later. (Dr. Richard Schwartz,
Vienna Pediatric Associates in Psychiatric Annals as reported in
NIDA Capsules)
6. Marijuana activates the same pleasure centers in the brain
that are targeted by heroin, cocaine and alcohol. (Dr. Gaetano Di
Chiara, University of Caligari, Italy)
7. Physiological effects of marijuana include an alteration of
heart rate. Use of marijuana may result in intense anxiety, panic
attacks or paranoia. (National Institute of Drug Abuse)
8. The daily use of 1 to 3 marijuana joints appears to produce
approximately the same lung damage and potential cancer risk as
smoking 5 times as many cigarettes. (UCLA) The study results
suggest that the way smokers inhale marijuana, in addition to its
chemical composition, increases the adverse physical effects. The
same lung cancer risks associated with tobacco also apply to
marijuana users, even though they smoke far less. (reported in NIDA
Capsules)
9. Benzopyrene is the chemical in tobacco that causes lung
cancer. An average marijuana cigarette contains nearly 50%
more benzopyrene than a tobacco cigarette. An average
marijuana cigarette contains 30 nanograms of this carcinogen
compared to 21 nanograms in an average tobacco cigarette (Marijuana
and Health, National Academy of Sciences, Institute of Medicine
Report, 1982) Benzopyrene suppresses a gene that controls growth of
cells. When this gene is damaged the body becomes more susceptible
to cancer. This gene is related to half of all human cancers and as
many as 70% of lung cancers.
10. Marijuana users may have many of the same respiratory
problems that tobacco smokers have, such as chronic bronchitis and
inflamed sinuses. (Marijuana
Facts: Parents Need to Know, National Institute on Drug Abuse )
11. Marijuana smokers, when compared to non marijuana smokers,
have more respiratory illness. (Polen et al. 1993).
12. Marijuana smoke produces airway injury, acute and
chronic bronchitis, lung inflammation, and decreased pulmonary
defenses against infection. Smoking one marijuana cigarette leads to
air deposition of four times as much cancer-causing tar as does
tobacco smoke (Dr. D. Tashkin, Western Journal of Medicine)
13. Heavy marijuana use can affect hormones in both males and
females. Heavy doses of the drugs may delay the onset of
puberty in young men. Marijuana also can have adverse effects on
sperm production. Among women, regular marijuana use can disrupt the
normal monthly menstrual cycle and inhibit the discharge of eggs
from the ovaries. (Marijuana
Facts: Parents Need to know, National Institute on Drug Abuse)
14. An "amotivational syndrome" can develop in heavy,
chronic marijuana users. It is characterized by decreased drive and
ambition, shortened attention span, poor judgment, high
distractibility, impaired communication skills, and diminished
effectiveness in interpersonal situations. (National Institute of
Drug Abuse)
15. Adults who smoked marijuana daily believed it helped them
function better, improved self-awareness and improved relationships
with others. However, researchers found that users were more willing
to tolerate problems, suggesting that the drug served as a buffer
for those who would rather avoid confronting problems than make
changes that might increase their satisfaction with life. The study
indicated that these subjects used marijuana to avoid dealing with
their difficulties and the avoidance inevitably made their problems
worse. Although users believed the drug enhanced understanding of
themselves, it actually served as a barrier against self-awareness.
(case studies by research team from Center for Psychosocial Studies
in New York.)
16. Marijuana and some of its compounds influence the immune
system and affect the body's ability to resist viruses, bacteria,
fungi and protozoa, and decreases the body's anti tumor activities.
Marijuana has the potential to alter the backup safeguards of
the immune system because it affects diverse types of cells in the
body. This could compromise the immune system's ability to screen
out cancer cells and eliminate infection. (Dr. Guy A. Cabral,
Professor, Medical College of Virginia, speaking at NlDA's National
Conference on Marijuana Use: Prevention, Treatment and Research.)
"Unfortunately, much of what is known about the human
pharmacology of smoked marijuana comes from experiments with plant
material containing about 2% THC or less, or occasionally up to 4%
THC. In addition, human experiments typically are done in laboratory
settings where only one or two smoked doses were administered to
relatively young, medically screened, healthy male volunteers well
experienced with the effects of marijuana. Females rarely
participated in past marijuana research because of prohibitions (now
removed) against their inclusion. Thus the clinical pharmacology of
single or repeated smoked marijuana doses given to older people or
to people with serious diseases has hardly been researched at all in
a controlled laboratory or clinic setting. Some of the very few
reports of experiments that have included older or sicker people,
particularly patients less experienced in using marijuana suggest
the profile of adverse effects may differ from healthy student
volunteers smoking in a laboratory experiment (Hollister, 1986a,
1988a)
THC administered alone in its pure form is the most thoroughly
research cannabinoid. Much of what has been written has been
inferred from the results of experiments using only pure THC.
Generally, in experiments actually using marijuana, the assumed dose
of marijuana was based only on the concentration of THC in the plant
material. The amounts of cannabidiol and other cannabinoids in the
plant also vary so that pharmacological interactions modifying the
effects THC may occur when marijuana is used instead of pure THC.
The result of this research strategy is that a good deal is known
about the pharmacology of THC, but experimental confirmation that
the pharmacology of a marijuana cigarette is indeed entirely or
mainly determined by the amount of THC it contains remains to be
completed. The scientific literature contains occasional hints that
the pharmacology of pure THC, although similar, is not always the
same as the clinical pharmacology of smoked marijuana containing the
same amount of THC (Graham 1976, Harvey 1985, Institute of Medicine
1982)" (Report to the Director, National Institutes of Health,
by the Ad-Hoc Group of Experts, "Workshop on the Medical
Utility of Marijuana.")
