A QUALITATIVE COMPARISON OF THE HEALTH RISKS OF ALCOHOL, CANNABIS, NICOTINE
AND OPIATE USE
way of assessing the health risk posed by cannabis use is a comparative qualitative
appraisal of its risks with those of other widely used recreational of its risks
with those of other widely used recreational drugs such as alcohol and tobacco
(ARF/WHO, 1981). The motive for such comparisons is to use a common standard
when making societal decisions about the control and regulation of cannabis
use. Like tobacco, cannabis is most commonly smoked, and like alcohol, cannabis
is commonly used for its intoxicating and euphoriant effects in developed societies
(although it may be used for more utilitarian reasons, such as, making heavy
physical work tolerable, in some developing countries). The opiates provide
a useful illicit drug class against which to calibrate the adverse effects of
cannabis since this class of drugs has a fearsome although not always deserved
reputation as a major risk to the health of young adults. Nonmedical use of
opiates is initially primarily for euphoria or for relief of pain.
this qualitative comparison we have avoided the necessity to comprehensively
review the vast literatures on the health effects of alcohol and tobacco by
using the following authorities as the warrant for our assertions about their
health risks: Anderson et al (1993); Holman et al's (1988) compendium of the
health effects of alcohol and tobacco; the Institute of Medicine (1987); the
International Agency for Research into Cancer (1990); Roselle et al (1993);
and the Royal College of Physicians (1987).
In the absence
of an authoritative current review of the health effects of the opioids as a
class of drugs, it was necessary to look to several sources to identify the
health effects of opioids. General pharmacological texts, and other reviews,
were used to describe the pharmacological effects of the opioids (e.g., Belkin
and Gold, 1991; Jacobs and Fehr, 1987; Duggan and North, 1983). In addition,
information on the chronic health effects and social consequences of illicit
opiates (injectable and non-injectable) and of methadone was taken from reports
of several longitudinal studies of opioid users (e.g. Vaillant, 1973; O'Donnell,
1969; Maddux and Desmond, 1981; Simpson, Joe, Lehman and Sells, 1986; Joe and
Simpson, 1987; 1990). These cohort studies typically involve populations in
contact with drug treatment services rather than representative samples of users.
The major risks
of acute cannabis use show some parallels with the acute risks of alcohol intoxication.
First, both drugs produce psychomotor and cognitive impairment, especially of
memory and planning. The impairment produced by alcohol increases risks of various
kinds of accident. It may also increase the likelihood of engaging in risky
behaviour such as dangerous driving, and unsafe sexual practices. While cannabis
intoxication increases the risks of casualties in hazardous situations, it remains
to be determined to what extent it increases the likelihood of engaging in risky
Alcohol and cannabis
intoxication appear to differ in their relation to intentional rather than accidental
casualties. Alcohol intoxication is strongly associated with aggressive and
violent behaviour. The relationship is complex, and the nature and extent of
drinking's causal effect remains controversial at the level of the individual
drinker (Pernanen, 1991; Martin, 1993; Pohorecky, Brick and Milgram, 1993).
But there is good causal evidence that changes in the level of alcohol consumption
affect the incidence of violent crime, at least in some populations (Room, 1983;
Lenke, 1990; Cook and Moore, 1993). There is also increasing evidence to indicate
that alcohol may play a role in suicide (Edwards et al., forthcoming). There
is little to suggest that causal relationship of cannabis use to aggression
or violence, at least in present-day developed societies.
is good evidence that substantial doses of alcohol taken during pregnancy can
produce a foetal alcohol syndrome. There is suggestive but far from conclusive
evidence that cannabis can also adversely affect the development of the foetus
when used during pregnancy. A clear equivalent for cannabis of the foetal alcohol
syndrome has not been established.
Third, there is
a major health risk of acute alcohol use that is not shared with cannabis.
In large doses alcohol can cause death by asphyxiation, alcohol poisoning, cardiomyopathy
and cardiac infarct. There are no recorded cases of overdose fatalities attributed
to cannabis, and the estimated lethal dose for humans extrapolated from animal
studies is so high that it cannot be achieved by recreational users.
The major acute
health risks that cannabis shares with tobacco are the irritant effects of smoke
upon the respiratory system, and the stimulating effects of both THC and nicotine
on the cardiovascular system, both of which can be detrimental to persons with
cardiovascular and respiratory diseases. For both drugs, the respiratory effects
do not apply to ingestion that is not by inhalation.
Some of the opioids
share with alcohol and cannabis an acute intoxicating effect, although the sedative
effect is more pronounced. Acute administration of heroin causes euphoria in
many users, although other opioids such as methadone do not have this effect
in tolerant individuals. The extent of euphoria is also affected by route of
administration. As is found with cannabis, some naive users report unpleasant
feelings with opiate use, specifically nausea and dysphoria. All opioids are
CNS depressants and as such can reduce level of consciousness and cause sleep.
on the effects of opiates on driving and other exacting skills is not well developed.
A maintenance dose in a tolerant user may produce little psychomotor or cognitive
impairment. A heroin user who has reached a stage of "nodding" is in no condition
to drive a car, but will probably have little inclination to do so. As with
cannabis, there is little direct epidemiological evidence of opiate-induced
casualties. One study showed that the driving-related skills of persons maintained
on stable doses of methadone were not impaired when assessed on a laboratory
task that is sensitive to the effects of alcohol (Chesher, Lemon, Gomal and
While there is
no risk of overdose associated with cannabis, use of illicit opioids carries
a real risk of overdose. High doses of most opioids can lead to suppression
of breathing rate and blood pressure and cause respiratory arrest. The risk
of overdose is worsened by use in combination with alcohol or other drugs, and
is thought to be worsened by variations in the potency of opiates obtained illegally.
cannabis, cause some suppression of hormone levels. These decreased hormonal
levels, however, do not necessarily result in infertility in men or women using
opioids\do for extended periods (Belkin and Gold, 1991; Duggan and North, 1983;
Martin and Martin, 1980). Like alcohol, tobacco and cannabis, the opiates have
been associated with miscarriage, foetal death and low birth-weight. There is
no clear relationship with an identifiable syndrome of foetal defects from opioids
that parallels foetal alcohol syndrome. Although poor nutrition and pre-natal
care clearly contribute to the risk of adverse outcomes in pregnant women addicted
to street drugs, even methadone maintenance has been found to result in higher
rates of pregnancy problems. Methadone and other orally administered opioids
have been shown to cause foetal death and low birthweight in laboratory animals
(Martin and Martin, 1980; Caviston, 1987; Woody and O'Brien, 1991).
There are a number
of risks of heavy chronic alcohol use some of which may be shared by chronic
cannabis use. First, heavy use of either drug increases the risk of developing
a dependence syndrome in which users experience difficulty in stopping or controlling
their use. There is strong evidence of such a syndrome in the case of alcohol
and reasonable evidence in the case of cannabis. A major difference between
the two is that withdrawal symptoms are either absent or mild after dependent
cannabis users abruptly stop their cannabis use, whereas the abrupt cessation
of alcohol use in severely dependent drinkers produces a well defined withdrawal
syndrome which can be potentially fatal.
is reasonable clinical evidence that the chronic heavy use of alcohol can produce
psychotic symptoms and psychoses in some individuals, either during acute intoxication
or during the process of withdrawal in dependent drinkers. There is some clinical
evidence that chronic heavy cannabis use may produce a toxic psychosis. One
prospective epidemiological study suggests that heavy cannabis use may precipitate
schizophrenia in predisposed individuals,. that is, those with a personal or
a family history of psychiatric disorder. There is better evidence that continued
cannabis use may worsen the course of schizophrenia.
Third, there is
good evidence that chronic heavy alcohol use can indirectly cause brain injury
- the Wernicke-Korsakov syndrome - with symptoms of severe memory defect and
an impaired ability to plan and organise. With continued heavy drinking, and
in the absence of vitamin supplementation, this injury may produce severe irreversible
cognitive impairment. There is good reason for concluding that chronic cannabis
use does not produce cognitive impairment of comparable severity. There is suggestive
evidence that chronic cannabis use may produce subtle defects in cognitive functioning,
that may or may not be reversible after abstinence.
is reasonable evidence that in the absence of countervailing cultural beliefs
chronic heavy alcohol use generally impairs occupational performance in adults
and educational achievements in adolescents. There is suggestive evidence that
chronic heavy cannabis use produces similar, albeit more subtle impairments
in occupational and educational performance of adults.
Fifth, there is
good evidence that chronic, heavy alcohol use increases the risk of premature
mortality from accidents, suicide and violence. There is no comparable evidence
for chronic cannabis use, although it is likely that dependent cannabis users
who frequently drive while intoxicated with cannabis would increase their risk
of accidental injury or death.
use has been accepted as a contributory cause of cancer of the oropharangeal
organs in men and women. There is suggestive clinical evidence that chronic
cannabis smoking may also be a contributory cause of cancers of the aerodigestive
tract. There is also some epidemiological evidence that alcohol use moderately
increases the risk of cancer of the breast in women and of the colon in both
use is a major cause of liver cirrhosis, accounting for upward of 80% of cases
in non-tropical countries with substantial alcohol consumption levels. Heavy
drinking is also implicated in gastritis, high blood pressure, stroke, cardiac
arrhythmias, cardiomyopathy, pancreatitis, and polyneuropathy. On the other
hand, regular drinking of small amounts of alcohol appears to reduce the risk
of coronary heart disease, particularly in older individuals with positive risk
factors such as tobacco smoking or a fatty diet. No equivalent protective effects
have been found for cannabis although there is some evidence for the therapeutic
usefulness of some cannabinoids (Hall et al, 1994).
The major adverse
health effects shared by chronic cannabis and tobacco smokers are chronic respiratory
diseases, such as chronic bronchitis, and probably, cancers of the aerodigestive
tract (i.e. the mouth, tongue, throat, oesophagus, lungs). The increased risk
of cancer in the aerodigestive tract is a consequence of the shared route of
administration by smoking. It is possible that chronic cannabis smoking also
shares the cardiotoxic properties of tobacco smoking, although this possibility
remains to be investigated. These respiratory risks could be avoided by a change
to the oral route of administration which would also reduce but not eliminate
the cardiovascular risk since THC affects the cardiovascular system when taken
is associated with a wide variety of other chronic health conditions for which
cannabis smoking has not so far been implicated. These include cancer of the
cervix, stomach, bladder and kidney, coronary heart disease, peripheral vascular
disease, and stroke, as well as cataracts and osteoporosis.
The specific health
effects of opioid use largely depend on the route of administration. The use
of injectable opiates carries risks not common to alcohol, tobacco or cannabis,
especially when associated with illegally obtained injectables and shared needles.
Injecting heroin or morphine can lead to trauma, inflammation and infection
at the site of administration. Liver damage in opiate addicts may be caused
by viral hepatitis contracted through needle sharing or from chronic alcohol
abuse. Serious infection such as endocarditis is also possible. Local tissue
and organ damage may also result from the adulterants in injection drugs obtained
on the street (Belkin and Gold, 1991). Intravenous drug use is a major concern
for the transmission of communicable diseases such as viral hepatitis and AIDS.
Chronic use of
non-injected opioids appears to carry little risk of adverse health effects
other than a modest effect on endocrine activity, some suppression of the immune
system which has similar implications to the immune suppression associated with
cannabis use, and chronic constipation.
While it is unclear
that a withdrawal syndrome exists for cannabis, physical dependence on opiates
has been recognised for centuries. Opiate withdrawal is associated with considerable
discomfort but is rarely life-threatening. The withdrawal syndrome is generally
less dangerous than rapid withdrawal from sedatives-hypnotics or from alcohol,
although it may be life-threatening in neonates. Despite the low risk, avoidance
of withdrawal appears to be a powerful motive for continued use of opiates among
very heavy users.
users may experience instability of mood, anorexia, lethargy and depression
which are related to acute drug effects. Opioids have not been linked to chronic
psychiatric disorders, but street addicts have a shortened life expectancy and
more frequently experience social and emotional problems. This is in part due
to their exposure to infection, violence and poor living conditions rather than
their drug use.