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Major Studies of Drugs and Drug Policy | ||||
Canadian Senate Special Committee on Illegal Drugs | ||||
Volume I - General Orientation |
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Chapter 7 - Cannabis: Effects and ConsequencesEffects and consequences of cannabis: what we were
told
During
the hearings, many witnesses told us what they knew about the effects of
cannabis. Some of this knowledge came from their own research work. Other
knowledge came from their professional experiences. And lastly, other knowledge
was either their interpretation of scientific literature or anecdotes. In this
section, we will not make distinctions between the testimony and we will not
evaluate its validity. We only want to highlight the richness, as well as the
complexity, of what we were told. Message number one is that drugs, including
cannabis, are harmful. (
) There is considerable misinformation about the
physiological consequences of cannabis use. There is no doubt that heavy use
has negative health consequences. The most important are in the following
areas: respiratory damage, physical coordination, pregnancy and postnatal
development, memory and cognition, and psychiatric effects. (...) [1][7] Generally, marijuana (cannabis) and its derivative
products are described in this context to distance the drug from the recognized
harm associated with other illegal drugs. This has been a successful yet
dangerous approach and contributes to the misinformation, misunderstanding and
increasing tolerance associated with marijuana use. Marijuana is a powerful
drug with a variety of effects. Marijuana users are subject to a variety of
adverse health consequences that include respiratory damage, impaired physical
coordination, problem pregnancy and postnatal deficits, impaired memory and
cognition, and psychiatric effects. Marijuana use is associated with poor work
and school performance and learning problems for younger users. Marijuana is
internationally recognized as a gateway drug for other drug use. Risk factors
for marijuana dependence are similar to those of other forms of drug abuse. (
)
It was the consensus of the international community to put marijuana and other
substances under international control. That decision was based on evidence of
its harmfulness to human health and its dependence potential. [2][8] I wish to briefly review two of what I believe are
fairly well-established, harmful effects of marijuana, and a number of other
areas where there is considerable contention. (
) By far the most consistent
and clear-cut effect of marijuana is disruption of short-term memory.
Short-term memory is usually described as "working" memory. It refers
to the system in the brain that is responsible for short-term maintenance of
information needed for the performance of complex tasks that demand planning,
comprehension and reasoning. The relatively severe impairment of working memory
may help to explain why, during the marijuana high, subjects have difficulty
maintaining a coherent train of thought or conversation. (
) Obviously this is
relevant if you are going to school stoned. (
) It is becoming increasingly
clear that cannabis is a drug on which regular users become dependent, and that
this adversely affects large numbers of people. [3][9] Marijuana has been shown to be associated with
reckless drivers and motor vehicle accidents. Evidence suggests that marijuana
may contribute to an appreciable number of traffic deaths and injuries in
Canada. It has been shown to negatively affect the academic and social
development of some adolescents. Marijuana can cause emotional and medical
problems. Chronic use may be associated with lung diseases such as bronchitis,
emphysema and cancer. A psychosis may develop in some individuals while other
psychiatric symptoms such as anxiety, low mood, depression and panic do occur.
Marijuana is known to be addictive. Although the rate of addiction varies, it
is between 5 per cent and 10 per cent. I should like to stress that addiction
is a disease and marijuana has the potential to be addictive to a genetically
predisposed group of individuals. [4][10] The evidence was that 95 per cent of the marijuana
users in Canada are low, occasional, moderate users. Their consumption of
marijuana does not impact on their health as long as they are healthy adults.
The other 5 per cent are chronic users, people who smoke one or more marijuana
cigarettes per day. If they continue to do that, they will ultimately get
chronic bronchitis from the smoking process. The same would be true if they
were to roll up the grass off their lawns and smoke that. They would inhale
heated material over their large airways and cause damage to them. There were
three primary vulnerable groups: pregnant women, which we submit is something
between the woman and her doctor; the mentally ill, particularly paranoid
schizophrenics (
) then, most importantly, immature youth. Young people who
become involved with marijuana - particularly on a regular basis - seem to
suffer from a disruption of their studies and the maturation process. As is the
case with most intoxicants, it is recommended that they not become involved
with them until they have matured. [5][11] I have one resource from the Center for Substance
Abuse Prevention in the U.S., where recent marijuana research and a number of
studies indicate some of the risks. We already know and accept that cannabis
has negative effects on many systems - respiratory, motor skills, memory and
immune - and that it creates drug dependency and tension. In addition, we now
know from numerous research studies that there is a definite and acute
withdrawal syndrome associated with chronic cannabis use. (
) There is research
that suggests there are effects on the developing fetus. (
) I will speak to
visual scanning, specifically, attention dysfunction in the form of impaired
visual scanning and related functioning. Visual scanning develops particularly
in early adolescence, so earlier onset is associated with some concerns there. [6][12] There are a number of negative health effects that
have been created in the lab or have been observed with long-term users (
).
There are, of course, health risks and negative health consequences with using
the substance, but the majority of those risks only occur under specific
circumstances. The majority of the risks are associated with long-term
persistent and frequent use, and therefore must be understood as such. There is
at this point agreement that the so-called dependence or withdrawal symptom may
arise with heavy chronic users, but it is very much limited to that small
population. (
) a seminal report by Hall and colleagues from Australia (
)
concluded that the major risks of cannabis use can be significantly reduced by
avoiding driving under the influence, by avoiding chronic and daily use, and by
avoiding deep inhalation. These were the key factors that allowed us to avoid
many of the major harms and risks associated with it. [7][13] In any event, we are talking about plant
derivatives that contain a number of psychoactive alkaloids. The psychoactive
effects are predominantly of mild euphoria and time distortion, though
disorientation and panic attacks may occur. The appreciation of music, art and
food are said to be enhanced, as is appetite, and this later function seems
important for one of the claimed medical benefits in offsetting the effects of
the chronic wasting syndrome in AIDS and the prolonged nausea that accompanies
chemotherapy. (
) Because the drug is usually smoked, it has acute and chronic
effects that are shared with tobacco. These include airway irritation, cough,
and probably with chronic use, bronchitis, chronic obstructive pulmonary
disease, and lung and pharyngeal cancers. Its impact on the immune system is
generally to impair the function of the immune system, but the impact on human
health of this impairment is probably minor. (
) The effects of cannabis
consumption on reproductive health are negative in animal studies. (
) This
obviously has some relevance to human health. However, human studies have yet
to show any measurable adverse impact beyond some evidence of adverse
behavioural and developmental impacts on the children of mothers who smoked
cannabis heavily during pregnancy. (
) The impact of cannabis on cognition is
well documented. Short-term memory is adversely affected and chronic use may
lead to chronic measurable defects in cognitive functioning. However, this may
be more the result of persistent chronic intoxication than impairment in the
substance and the working of the brain. Psychomotor skills are adversely
affected by cannabis use. Driving or operating heavy machinery when intoxicated
is contraindicated. Again, in contradistinction to alcohol, cannabis
intoxication tends to slow drivers down rather than increase their speeds.
Similarly, cannabis smokers tend not to be involved in acts of physical
violence and aggression, and violence and aggression when intoxicated is
reportedly very rare. Cannabis use may provoke schizophrenic symptoms in those
with active schizophrenia or schizophrenic tendencies. Panic attacks and
dysphoria are also mentioned in the literature. There is an amotivational
syndrome described in the literature and cannabis is said to induce it, but
most researchers have discredited that over the last decade. (
) Concerns have
legitimately been raised about the effects of cannabis consumption on
adolescent development. As use tends to peak in late adolescence, this is an
important consideration. The adverse effects that have been noted include an
association with risk of discontinuation of high school, job instability and
progression to the use of harder drugs. The degree to which these associations
are causal is very controversial. Alternative hypotheses are that cannabis use,
like adolescent alcohol use, early onset of sexual activity, and tobacco
smoking, are in fact markers for other risks of adverse social conditions (
)
All researchers agree, however, that intoxication interferes with academic
prowess. Recent studies seem to demonstrate measurable though reversible drops
in IQ associated with heavy, persistent cannabis use and that engagement in
illicit activities carries substantial risks, especially perhaps for youth
whose connections to the school community are tenuous at best. [8][14] I would like to first focus on the acute effects
and then on the chronic effects. "Acute effects" are those effects
that you experience during the course of action of a single dose. In the
nervous system that includes a period of several hours in which (
) you become
"chemically stupid." Side effects include decreased arousal and
drowsiness, which acts together with the drowsiness produced by alcohol and
other central nervous system depressants. Other side effects are impaired
short-term memory, slowed reactions, less accuracy in test performance and less
selectivity of attention. (
) Low doses generally produce the effects that
cause people to like smoking pot. They include mild euphoria, relaxation,
increased sociability and a non-specific decrease in anxiety. However, high
doses produce a bad mood, anxiety and depression. There can be increased
anxiety to the point of panic or even an acute toxic psychosis which,
fortunately, is of very short duration and goes away when the drug effect wears
off. High doses cause impaired motor coordination, unsteadiness of control and
decreased muscle tone, which is therapeutically useful. (
) With low doses,
perception is enhanced. That is part of the pleasure. In high doses, the same
action produces sensory distortion, hallucinations and the acute toxic
psychosis to which I have already referred. (
) It does not seriously affect
the cardiovascular system. (
) As to chronic effects, in the central nervous
system there is impaired memory, vagueness of thought, decreased verbal
fluency, and learning deficits in chronic, heavy users. I emphasize
"heavy" because the social user does not, by and large, show any
significant health effects. Neither does the social user of alcohol. (
) These
effects on cognitive functions fortunately tend to go away if the heavy user
stops, for whatever reason. As long as use continues, there is a chronic
intoxication, apathy, confusion, muddled thinking, depression, and sometimes
paranoia. (
) Cannabis dependence, as defined in the conventional diagnostic
criteria for dependence as set out in the latest edition of the American
Psychiatric Association, or the equivalent publication of the World Health
Organization, has been well documented in regular, heavy users. Numerous
studies now show that a significant percentage of regular users are dependent.
In some studies in Australia of long-term heavy users, mainly daily users for
periods of 15, 17, 20 years, 60 per cent or more of them met the diagnostic
criteria (
). Tolerance has been shown. By and large, it is not a terribly
serious effect, and the physical withdrawal syndrome is not severe.
Nevertheless, it is there, which indicates that physical dependence, in
addition to psychological dependence, occurs as well. [9][15] The long-term chronic effects of cannabis essentially
cause the following symptoms: memory loss, faulty attention and concentration,
a slow-motivation syndrome of passivity and low initiative, increased risk of
respiratory disease, more specifically asthma, bronchitis and emphysema and a
higher risk of cancer. (
) There may be hormone problems causing low fertility
in men and women. In men, this can cause the development of breasts which is
very unesthetic (
). Finally, in the long-term, it can also cause lower
resistance to infectious disease. [10][16] As we can see, opinions sometimes agree and
often differ. They agree at least on the nature of the consequences that may be
of concern. One by one, we have seen effects that were physiological (risks of
cancer, effects on reproduction and the immune system, deterioration of brain
cells), effects that were psychological (amotivational syndrome, risks of
psychosis, impaired cognitive function and memory in particular), and effects
that were social (affecting the family and work, as well as the ability to drive
vehicles and operate machinery). Opinions differ primarily on the scope of the
conclusions that can be drawn from this knowledge. To what extent, in fact, can
we generalize about the effects we observe in often small and rarely random
samples of subjects? Also, to what extent can we generalize about the data on
chronic users who represent as we saw in the previous chapter only a small
percentage of cannabis users? And especially, to what extent does this data
allow us to establish causal relationships? The
Committee also finds that most witnesses stressed the negative aspects and
rarely the positive. However, if people use drugs in general, and cannabis in
particular, surely it isnt just to destroy themselves or because these drugs
have only negative effects. Given the limitations of making any comparison
between substances, we can still draw a parallel with alcohol: most of us know
the pleasure of sharing a glass of wine with friends over a good meal, just as
we also know the dangers of alcohol abuse and alcoholism. The Committee also
notes that it is difficult, even for the most experienced researchers, to sift
through the knowledge without assigning it a valence relative to the direction
public policy should take. The same knowledge may be interpreted negatively
here and more moderately there, based on the interpreters preconceptions of
the best choice for public policy. We are not immune to this bias. Moreover,
we do not deny that we had preconceptions, derived from our personal histories,
our reading, and the hearings we held in 1996 to review Canadas drug
legislation. Among these preconceptions, which oriented our reading of the
testimony, at least at first, we note:
This
being said, we did not work in isolation. Not only were we accompanied by our
research team sociologists, lawyers, criminologists throughout our work,
not only were we also under the close surveillance of the witnesses in a way
and of the public in a larger sense, but primarily, other committees, in other
countries, have conducted similar reviews in recent years. Their work was a source
of inspiration and knowledge and as well a benchmark against which to compare
our own conclusions. [1][7]
Testimony of Michael J. Boyd, Chair of the Drug Abuse
Committee and Deputy Chief of the Toronto Police Service, for the
Canadian Association of Chiefs of Police, Special Senate Committee on Illicit
Drugs, First Session of the Thirty-Seventh Parliament, Issue No. 14, page: 74. [2][8]
Testimony of Dale Orban, Detective Sergeant, Regina Police Service, for the
Canadian Police Association, Special Senate Committee on Illicit Drugs, First
Session of the Thirty-Seventh Parliament, Monday, May 28, 2001, Issue 3, page:
47. It should be immediately noted that the last statement is completely false
as we will see in Chapters 19 and 12 on international agreements and
Canadian legislation that have placed cannabis on the list of controlled drugs
since 1924, with no knowledge of its physical or psychological effects at that
time, and for completely different reasons, when there were any. [3][9] Dr. Mark Zoccolillo, Professor of Psychiatry
and Assistant Professor of Pediatrics, McGill University and the Montreal
Children's Hospital, Special Senate Committee on Illicit Drugs, Second Session
of the Thirty-Sixth Parliament, October 16, 2000, Issue No. 1, page 77. [4][10] Dr. Bill Campbell, President, Canadian
Society of Addiction Medicine, Special Senate Committee on Illicit Drugs, First
Session, Thirty-Seventh Parliament, March 11, 2002, Issue No. 14, page: 56. [5][11] Mr. John Conroy, Barrister, Special Senate
Committee on Illicit Drugs, First Session of the Thirty-Seventh Parliament,
March 11, 2002, Issue No. 14, page 11. [6][12] Dr Colin Mangham, Director, Prevention
Source BC., Special Senate Committee on Illicit Drugs, First Session of the
Thirty-Seventh Parliament, September 17, 2001, Issue No. 6, page: 71. [7][13] Dr. Benedikt Fischer, Professor, Department of Public Health
Sciences, University of Toronto, Special Senate Committee on Illicit
Drugs, First Session of the Thirty-Seventh Parliament,
September 7, 2001, Issue No. 6, page 9. [8][14] Dr. Perry Kendall, Health Officer for the
Province of British Columbia, Special Senate Committee on Illicit Drugs, First
Session of the Thirty-Seventh Parliament, September 17, 2001, Issue No. 6, pages 33-33. [9][15] Dr. Harold Kalant, Professor Emeritus at the
University of Toronto, Special Senate Committee on Illicit Drugs, First Session
of the Thirty-Seventh Parliament, June 11, 2001, Issue No. 4, pages 74-76. [10][16] Dr. Mohamed ben Amar, Professor of
Pharmacology and Toxicology, University of Montreal, Special Senate Committee
on Illicit Drugs, First Session of the Thirty-Seventh Parliament,
June 11, 2001, Issue No. 4, pages 9-10. |