Is cannabis use a risk to health?

A look at the evidence


Claims of various degrees of harmfulness and danger associated with the smoking of cannabis are often cited by prohibitionists and those who favour regulated legalisation alike.

see Pot Smokers Just As Healthy - Study: National Post (Canada), 11 June 2001

Whilst many people agree that prohibition is unjust and ineffective, they differ in their opinions on the needs for regulations. Whilst few would want unnecessary regulations and limitations legislated onto cannabis once legal, few also would want to see no regulations installed if indeed necessary. It is therefore vital that we attempt to reach some sort of conclusion on the harm or potential harm through individual or widespread cannabis use.

I have personally read many reports from scientific and empirical studies on cannabis use, as well as some of those based upon laboratory tests carried out on mice, rats, rabbits and monkeys, using concentrated and synthetic THC - tetrahydrocannabinol - one of the main active ingredients found in the parts of the cannabis plant used recreationally and medically, particularly the tops and heads.

My own studies of the evidence from both sides has led me to the following conclusions:

1) All of the allegations of harm are based upon dubious work, laboratory experiments not involving cannabis and not involving tests on humans, and unreliable anecdote often exaggerated and g by drug workers.

2) Cannabis is indeed "remarkably safe" and free from danger, barring of course the obvious dangers of being hit over the head with a large lump of resin.

"We.. say that on the medical evidence available, moderate indulgence in cannabis has little ill-effect on health, and that decisions to ban or legalise cannabis should be based on other considerations.": The Lancet, vol 352, number 9140, November 14 1998

As it is nonsensical to attempt to prove any substance to be completely harmless under all circumstances, I am tackling this issue by listing the various harm allegations and counteracting them with quotes from and references to the experts.

We must be careful to distinguish the empirical evidence from studies of the health effects of herbal and pure cannabis on people who smoke it and anecdotes or hypotheses base on studies using chemical THC and other extracts on mice and monkeys in the laboratory.

The Report of the World Health Organisation, so often cited by those who claim cannabis to be a health risk, says this:

"A great many assumptions have been made in extrapolating from health effects observed in laboratory animals to the probable health effects of equivalent doses and patterns of use in humans. In addition, there may be problems in extrapolating studies with pure THC to human experience with crude cannabis preparations. The plant material contains many other compounds, both cannabinoid and non-cannabinoid in nature and the possibility must always be considered that differences between experimental and clinical observations may be due in part to the effects of these other substances."


Alun Buffry, BSc., Dip Com (Open)


Myth: Cannabis is toxic / poisonous


DATED: SEP 6 1988

Findings of Fact:

"4. Nearly all medicines have toxic, potentially lethal effects. But marijuana is not such a substance. There is no record in the extensive medical literature describing a proven, documented cannabis-induced fatality.

"5. This is a remarkable statement. First, the record on marijuana encompasses 5,000 years of human experience. Second, marijuana is now used daily by enormous numbers of people throughout the world. Estimates suggest that from twenty million to fifty million Americans routinely, albeit illegally, smoke marijuana without the benefit of direct medical supervision. Yet, despite this long history of use and the extraordinarily high numbers of social smokers, there are simply no credible medical reports to suggest that consuming marijuana has caused a single death.

"6. By contrast aspirin, a commonly used, over-the-counter medicine, causes hundreds of deaths each year.

"7. Drugs used in medicine are routinely given what is called an LD-50. The LD-50 rating indicates at what dosage fifty percent of test animals receiving a drug will die as a result of drug induced toxicity. A number of researchers have attempted to determine marijuana's LD-50 rating in test animals, without success. Simply stated, researchers have been unable to give animals enough marijuana to induce death.

"8. At present it is estimated that marijuana's LD-50 is around 1:20,000 or 1:40,000. In layman terms this means that in order to induce death a marijuana smoker would have to consume 20,000 to 40,000 times as much marijuana as is contained in one marijuana cigarette. NIDA-supplied marijuana cigarettes weigh approximately .9 grams. A smoker would theoretically have to consume nearly 1,500 pounds of marijuana within about fifteen minutes to induce a lethal response.

"9. In practical terms, marijuana cannot induce a lethal response as a result of drug-related toxicity.

"10. Another common medical way to determine drug safety is called the therapeutic ratio. This ratio defines the difference between a therapeutically effective dose and a dose which is capable of inducing adverse effects.

"11. A commonly used over-the-counter product like aspirin has a therapeutic ratio of around 1:20. Two aspirins are the recommended dose for adult patients. Twenty times this dose, forty aspirins, may cause a lethal reaction in some patients, and will almost certainly cause gross injury to the digestive system, including extensive internal bleeding.

"12. The therapeutic ratio for prescribed drugs is commonly around 1:10 or lower. Valium, a commonly used prescriptive drug, may cause very serious biological damage if patients use ten times the recommended (therapeutic) dose.

"13. There are, of course, prescriptive drugs which have much lower therapeutic ratios. Many of the drugs used to treat patients with cancer, glaucoma and multiple sclerosis are highly toxic. The

therapeutic ratio of some of the drugs used in antineoplastic therapies, for example, are regarded as extremely toxic poisons with therapeutic ratios that may fall below 1:1.5. These drugs also have very low LD-50 ratios and can result in toxic, even lethal reactions, while being properly employed.

"14. By contrast, marijuana's therapeutic ratio, like its LD-50, is impossible to quantify because it is so high."


In the journal FUNDAMENTAL AND APPLIED TOXICOLOGY, Dr. William Slikker, director of the Neurotoxicology Division of the National Center for Toxicological Research (NCTR), described the health of monkeys exposed to very high levels of cannabis for an extended period:

"The general health of the monkeys was not compromised by a year of marijuana exposure as indicated by weight gain, carboxyhemoglobin and clinical chemistry/hematology values."

(TOXICOLOGY LETTERS, No Increase in Carcinogen-DNA Adducts in the Lungs of Monkeys Exposed Chronically to Marijuana Smoke, 1992, Dec;63 (3): 321-32.

THE ARKANSAS TIMES (Refer Madness. 16 Sept 1993) asked Dr. Merle Paule of NCTR about evidence of cannabis toxicity and the health of the monkeys in the study, Dr. Paule said,

"There's just nothing there. They were all fine."

Myth: Cannabis intoxicates

This is really a matter of semantics, as, strictly speaking, a non-toxic substance cannot 'intoxicate'.

"intoxication" is usually and often detectable simply by a detrimental effect upon motor and cognitive skills; these are covered below.

Myth: Cannabis is addictive

Here we must distinguish between firstly, addictiveness and dependency, and secondly, between medical and psychological dependency.

Medical dependency is not really the issue here, since it is perfectly natural and acceptable for a person to be dependent upon a medicine to ease their suffering, given that the medicine is at least reasonably and acceptably safe.

TRENDS IN PHARMACOLOGICAL SCIENCES: Neurobiology of Marijuana Abuse. 1992, 13:201-206. pg. 203:

"research shows cannabis has limited potential for development of...psychological dependence due to the weak reinforcing properties of Delta-9-THC."

BRAIN RESEARCH JOURNAL: Chronic cannabinoid administration alters cannabinoid receptor binding in rat brain: a quantitative autoradiographic study. 1993, 616:293-302. pg. 300.

"cannabinoid dependence and withdrawal phenomena are minimal."

The Shafer Commission (USA) of 1970 said:

"Marijuana does not lead to physical dependency, although some evidence indicates that the heavy, long-term users may develop a psychological dependence on the drug"

The Panama Canal Zone Military Investigations (US Military, 1929) said:

"There is no evidence that Marihuana as grown and used [in the Canal Zone] is a 'habit-forming' drug."

In 1997, (R. v Clay), Ontario Justice John McCart (Canada) ruled, "Cannabis is not an addictive substance." B.C. Justice F.E. Howard in a similar case confirmed his findings in 1998.

US Department of Health and Human Services, 1991:

"Given the large population of marijuana users and the infrequent reports of medical problems from stopping use, tolerance and dependence are not major issue at present."

("Drug Abuse and Drug Abuse Research, Rockville, MD, (1991) p C3

Myth: Cannabis causes hallucinations

Report of the Australian Government, 1996: "Cannabis has been erroneously classified as a narcotic, as a sedative and most recently as an hallucinogen. While the cannabinoids do possess hallucinogenic properties, together with stimulant and sedative effects, they in fact represent a unique pharmacological class of compounds. Unlike many other drugs of abuse, cannabis acts upon specific receptors in the brain and periphery. The discovery of the receptors and the naturally occurring substances in the brain that bind to these receptors is of great importance, in that it signifies an entirely new pathway system in the brain."

Myth: Cannabis causes cancer

BOSTON, Jan. 30, 1997 (UPI):

"The U.S. federal government has failed to make public its own 1994 study that undercuts its position that marijuana is carcinogenic - a $2 million study by the National Toxicology Program. The program's deputy director, John Bucher (, says the study "found absolutely no evidence of cancer." In fact, animals that received THC had fewer cancers. Bucher denies his agency had been pressured to shelve the report, saying the delay in making it public was due to a personnel shortage.


"Marijuana Use and Mortality": AMERICAN JOURNAL OF PUBLIC HEALTH, April 1997:

TABLE 2 Relative Risk of Death for Ever Users and Current Users of Marijuana, by Sex and Cause of Death: Kaiser Pemanente Medical Care Program Members (n = 65,171), Oakland and San Francisco, June 1979 through December

1985 - section of table regarding cancer (Neoplasms) as the cause of death:


Ever Users Relative Risk of Cancer Death

Full Model 0.78

Non-smokers/ Occasional Drinkers 0.46

Current Users

Full Model 0.97

Non-smokers/ Occasional Drinkers 0.75


Ever Users

Full Model 0.82

Non-smokers/ Occasional Drinkers 0.70

Current Users

Full Model 0.86

Non-smokers/ Occasional Drinkers 0.56

Here, numbers less than one for Relative Risk of Cancer Death represent a lower rate of fatal cancer among marijuana smokers in the large Kaiser Study from California. For example, women who are current marijuana smokers but did not smoke tobacco were found to have only 56% of the risk of cancer death as compared to other women who were non-smokers of both tobacco and marijuana.

Not only is the evidence linking cannabis smoking to cancer negative, but the largest human studies cited indicated that cannabis users had lower rates of cancer than nonusers. What's more, those who smoked both cannabis and tobacco had lower rates of lung cancer than those who smoked only tobacco-a strong indication of chemoprevention. Even more, in 1975 researchers at the Medical College of Virginia found that cannabis showed powerful antitumour activity against both benign and malignant tumours (the government then banned all future cannabis/cancer research).

(The Emperor Wears No Cloths. Jack Herer, Queen of Clubs Pub, 1991)

(Ganja in Jamaica: A Medical Anthropological Study of Chronic Marijuana Use. 1975. Anchor Books)

(Cannabis in Costa Rica: A Study of Chronic Marijuana Use, 1980-82, Institute for the Study of Human Issues, 3401 Science Center Philadelphia, PA.)

The NEW ENGLISH DISPENSATORY of 1764 recommends boiled cannabis roots for the elimination of tumours.(Marijuana: The First 12,000 Years. Plenum Press, 1980)

Powerful evidence that cannabis not only does not cause cancer, but that it may prevent and even cure cancer.<>


Myth: Cannabis smoking damages the lungs

Researchers at the University of California (UCLA) School of Medicine have announced the results of an 8 - year study into the effects of long-term cannabis smoking on the lungs. In Volume 155 of the American Journal of Respiratory and Critical Care Medicine, Dr. D.P. Tashkin reported "Findings from the present long-term, follow-up study of heavy, habitual marijuana smokers argue against the concept that continuing heavy use of marijuana is a significant risk factor for the development of [chronic lung disease. ..Neither the continuing nor the intermittent marijuana smokers exhibited any significantly different rates of decline in [lung function]" as compared with those individuals who never smoked marijuana. Researchers added: "No differences were noted between even quite heavy marijuana smoking and non-smoking of marijuana."

Myth: Cannabis suppresses the immune system. Two studies in 1978 and 1988 showed that cannabis actually stimulated the immune system

From: "Exposing Marijuana Myths:(The Lindesmith Center)" "False: Marijuana Impairs Immune System Functioning "It has been widely claimed that marijuana substantially increases users' risk of contracting various infectious diseases. First emerging in the 1970s, this claim took on new significance in the 1980s, following reports of marijuana use by people suffering from AIDS.


"The principal study fueling the original claim of immune impairment involved preparations created with white blood cells that had been removed from marijuana smokers and controls. After exposing the cells to known immune activators, researchers reported a lower rate of transformation in those taken from marijuana smokers.

"However, numerous groups of scientists, using similar techniques, have failed to confirm this original study. "In fact, a 1988 study demonstrated an increase in responsiveness when white blood cells from marijuana smokers were exposed to immunological activators.

"Studies involving laboratory animals have shown immune impairment following administration of THC, but only with the use of extremely high doses. For example, one study demonstrated an increase in herpes infection in rodents given doses of 100 mg/kg/day -- a dose approximately 1000 times the dose necessary to produce a psychoactive effect in humans.

"There have been no clinical or epidemiological studies showing an increase in bacterial, viral, or parasitic infection among human marijuana users. In three large field studies conducted in the 1970s, in Jamaica, Costa Rica and Greece, researchers found no differences in disease susceptibility between marijuana users and matched controls.

"Marijuana use does not increase the risk of HIV infection; nor does it increase the onset or intensity of symptoms among AIDS patients. In fact, the FDA decision to approve the use of Marinol (synthetic THC) for use in HIV-wasting syndrome relied upon the absence of any immunopathology due to THC.

"Today, thousands of people with AIDS are smoking marijuana daily to combat nausea and increase appetite. There is no scientific basis for claims that this practice compromises their immune responses. Indeed, the recent discovery of a peripheral cannabinoid receptor associated with lymphatic tissue should encourage aggressive exploration of THC's potential use as an immune-system stimulant."

Marijuana Myths, Marijuana Facts": Lynn Zimmer Ph.D. and John P. Morgan M.D.: "At the 1981 conference on marijuana sponsored by the World Health Organisation and Canada's Addiction Research Foundation, reviewers of the research literature on immunity reported "There is no conclusive evidence that cannabis predisposes man to immune dysfunction". A few years late, in approving THC (Marinol) for use as a medicine, the FDA found no convincing evidence that THC caused immune impairment. In 1992, the FDA approved Marinol as an appetite stimulant specifically for AIDS patients, who have serious immunosuppression."Marijuana Myths, Marijuana Facts": Lynn Zimmer Ph.D. and John P. Morgan M.D. ISBN 0-9641568-4-9; page 107.Munson and Fehr (1983) note 15, page 338

Food and Drug Administration, "Unimed's Marinol (Dronabinol) Lau, R.J. et al "Phytohemagglutinin-Induced Lymphocyre Transformations in Humans Receiving Delta-9-Tetrahydrocannabinol," Science 192, 805-07 (1976)Dax, EM. Et al., "The Effects of 9_ENE-Tetrahydrcannabinol on Hormone Release and Immune Function," Journal of Steroid Biochemistry 34: 263-70 (1989)Myth: Cannabis causes impotency / infertility

From: "Exposing Marijuana Myths: (The Lindesmith Center)" page 93;"Studies of men in the general population have also failed to find differences in the testosterone levels of marijuana users and nonusers. "There is no convincing evidence of infertility related to marijuana consumption in humans. "There are no epidemiological studies showing that men who use marijuana have higher rates of infertility than men who do not. Nor is there evidence of diminished reproductive capacity among men in countries where marijuana use is common."

Abel, E.L., et al, "Marijuana and Sex: A Critical Survey," Drug and Alcohol Dependence 8: 1-22 (1981)

Ehrenkranz, J.R.L. and Hembee, WC., "Effects of Marijuana on Male Reproductive Function," Psychiatric Annals 16: 243-49 (1986)

Cushman, P, "Plasma Testosterone Levels in Healthy Male Marijuana Smokers," American Journal of Drug and Alcohol Abuse 2: 269-75 (1975)

Block, R I, et al, "Effects of Chronic Marijuana Use of Testosterone, Luteinizing Hormone, Follicle Stimulating Hormone, Prolactin and Cortisol in Men and women,"Drug and Alcohol Dependence 28,: 121-28 (1991)

Myth: Cannabis destroys short-term memory

The Australian Government Report 1996:

"The weight of the available evidence suggests that the long-term heavy use of cannabis does not produce any severe impairment of cognitive function."

Myth: Cannabis detrimentally effects motor co-ordination / driving skill

Crancer Study, Washington Department of Motor Vehicles:

"Simulated driving scores for subjects experiencing a normal social 'high' and the same subjects under control conditions are not significantly different. However, there are significantly more errors for alcohol intoxicated than for control subjects"

U.S. Department of Transportation, National Highway Traffic Safety Administration (DOT HS 808 078), Final Report, November 1993:"THC's adverse effects on driving performance appear relatively small"

Sutton (1983) also found that cannabis had little effect on actual driving performance. "Driving in traffic, however, while showing a trend toward poorer performance, was not significantly affected, and the effects of cannabis were much more variable."

The Australian Government Report, 1996, page 6) "There is no controlled epidemiological evidence that cannabis users are at increased risk of being involved in motor vehicle or other accidents.

Myth: Cannabis detrimentally effects cognitive skills

US: Cannabis Use and Cognitive Decline in Persons under 65 Years of Age

Publication date: 1 May 1999

Source: American Journal of Epidemiology

Copyright: 1999 Johns Hopkins University School of Hygiene and Public Health

Ref: Am J Epidemiol 1999; 149:794-800

Mail: 111 Market Place, Suite 840, Baltimore MD 21202 U.S.A.

<"> Website

Authors: Constantine G. Lyketsos, Elizabeth Garrett, Kung-Yee Liang, and James C. Anthony (Osler 320, The Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287-5371)

"The purpose of this study was to investigate possible adverse effects of cannabis use on cognitive decline after 12 years in persons under age 65 years. This was a follow-up study of a probability sample of the adult household residents of East Baltimore. The analyses included 1,318 participants in the Baltimore, Maryland, portion of the Epidemiologic Catchment Area study who completed the Mini-Mental State (MMSE) examination during three study waves in 1981, 1982, and 1993--1996.

Individual MMSE score differences between waves 2 and 3 were calculated for each study participant. After 12 years, study participants' scores declined a mean of 1.20 points on the MMSE (standard deviation 1.90), with 66% having scores that declined by at least one point.Significant numbers of scores declined by three points or more (15% of participants in the 18--29 age group). There were no significant differences in cognitive decline between heavy users, light users, and nonusers of cannabis.

There were also no male-female differences in cognitive decline in relation to cannabis use. The authors conclude that over long time periods, in persons under age 65 years, cognitive decline occurs in all age groups

This decline is closely associated with ageing and educational level but does not appear to be associated"

Ethiopian Zion Coptic Church Study, 1980

"Some participants had smoked at least two to four large cigarettes (each containing 1/4 to 1/2 ounce of cannabis) over 16 hours a day for periods of up to 50 years.

"...the most impressive thing... is the true paucity of neurological abnormalities.

"Heavy cannabis consumers suffered no apparent psychological or physical harm. "Schaeffer: A Neuropsychological Evaluation; A Case History"...I.Q.'s of Zion Coptics increased after they began to use ganga"

US Jamaican Study 1974:

"No impairment of physiological, sensory and perceptual performance, tests of concept formation, abstracting ability, and cognitive style, and tests of memory"

Myth: Cannabis causes a-motivation / laziness

We must of course distinguish between those people who are naturally or by habit or psychological so set as lazy or a-motivated, and any such a-motivation caused by cannabis consumption.

Dr. Andrew Weil (Rubin & Comitas Ganja in Jamaica, 1975) said "a-motivation [is] a cause of heavy marijuana smoking rather than the reverse"

In 1997, (R. v Clay), Ontario Justice John McCart (Canada) ruled, "Cannabis ... does not cause a motivational syndrome." His findings were confirmed by B.C. Justice F.E. Howard in a similar case in 1998

Myth: Cannabis use leads to the use of hard drugs

Considering the millions of people in the UK, and the hundreds of millions around the world, who have used cannabis for short or long periods, it is clear that if it led to the use of hard and addictive drugs there would be many more new addicts that we have seen.

We must, here, also remember that under the UK and other government policies of "tackling drugs together", under a regime that prohibits hard drugs alongside cannabis, where the supplies remain in criminal control, it is often the case that people may be led from one substance to another by their peers and by their suppliers. This does not of course mean that cannabis itself is a gateway or hard drug use.

We must also remember that at least a proportion of cannabis users may be people prone to trying other substances, whether by way of n, research, 'spiritual' quest, or psychological imbalance.

The LaGuardia sub-committee of New York 1944 said:

"The use of marijuana does not lead to morphine or heroin or cocaine addiction and no effort is made to create a market for these narcotics by stimulating the practice of marijuana smoking"

"Marijuana: Facts for Teens." U.S. Department of Health and Human Services. Washington, D.C. 1995, p.10.: "Most marijuana users do not go on to use other drugs." :

Jack Straw, The Daily Telegraph, 3 April 2000: "While it is undoubtedly the case that many drug addicts started with cannabis, to claim that taking cannabis is bound to lead to hard drugs has always seemed to me far-fetched."

Drugs Policy in the Netherlands (1995): Dutch Ministry of Health, Welfare and Sport "Moreover, users of soft drugs do not as a rule tend to experiment with hard drugs, such as heroin or cocaine; this is indeed the intention of the policy of keeping the markets separate. There is little use of heroin and cocaine among minors in the Netherlands, and the trend is towards even less. "Myth: Increased availability will lead to increased usage"

Drugs Policy in the Netherlands (1995): Dutch Ministry of Health, Welfare and Sport"4.1. Extent and nature of cannabis use

"The decriminalisation of the possession of soft drugs in 1976 did not result in increased use. The level of consumption stabilised in the first few years after the Opium Act was amended. According to national figures, use again increased somewhat between 1984 and 1994, a trend which has also been observed elsewhere. Indeed, the United States has experienced a considerable increase in recent years. "Both as regards the extent of cannabis use and trends in use, the Netherlands differs very little from other countries.

"As already indicated, the number of users of soft drugs has increased after falling in the 1970s. Patterns of consumption are overwhelmingly recreational, though among certain specific categories of young people, such as chronic truants and street children, the use of cannabis can be described as very substantial and intensive.

"The policy pursued by the Netherlands does not appear to have led to an increase in use, though there are indications that the existence of freely accessible coffee shops means that certain users continue to use the drugs for longer.

"Conclusions and policy intentions

"The decriminalisation of the possession of quantities of soft drugs for personal use and the existence of sales points tolerated under certain circumstances by the authorities have not resulted in a worryingly high level of consumption among young people. Moreover, users of soft drugs do not as a rule tend to experiment with hard drugs, such as heroin or cocaine; this is indeed the intention of the policy of keeping the markets separate. There is little use of heroin and cocaine among minors in the Netherlands, and the trend is towards even less.

"The effects of partial decriminalisation on cannabis use in South Australia, 1985 to 1993 National Drug and Alcohol Research Centre, University of New South Wales, Sydney Aust J Public Health, 19: 3, 1995 Jun, 281-7:"

In 1987 the Cannabis Expiration Notice scheme decreased penalties for the personal use of cannabis in South Australia. Data from four National Campaign Against Drug Abuse (NCADA) household drug-use surveys covering the period 1985 to 1993 were analysed to measure the effect of the decriminalisation on cannabis use. The main outcomes used were the self-reported prevalence rates of having ever used cannabis and current weekly use. Logistic regression was used to control for the potentially confounding effects of age and sex. Other outcomes were rates of having ever been offered cannabis and willingness to use cannabis if offered it. Between 1985 and 1993 the adjusted prevalence rate of ever having used cannabis increased in South Australia from 26 per cent to 38 per cent. There were also significant increases in Victoria and Tasmania, and to a lesser extent in New South Wales. The increase in South Australia was not significantly greater than the average increase (P = 0.1). Adjusted rates of weekly use increased between 1988 and 1991 in South Australia, but did not change through 1993. Although the effect was in the direction of a greater increase in South Australia, this was not statistically significant when compared to increases in the rest of Australia (P = 0.07). The greatest increase in adjusted weekly use occurred in Tasmania between 1991 and 1993, from 2 per cent to 7 per cent. Although the NCADA survey data indicate that there were increases in cannabis use in South Australia in 1985-1993, they cannot be attributed to the effects of partial decriminalisation, because similar increases occurred in other states"

And now, some general quotes on the health effects of smoking cannabis:

March 20, 1997, Sydney, Australia: The National Drug and Alcohol Research Centre in Australia. The study, which involved interviews with 268 marijuana smokers and 31 non-using partners and family members, is one of the first ever conducted in Australia to determine the effects of long-term marijuana use. Its findings were reported by the Sydney Morning Herald last month. "We don't see evidence of high psychological disturbance among the [long- term users,]" said chief investigator David Reilly. "The results seem unremarkable; the exceptional thing is that the respondents are unexceptional. "The Report of the Australian Government 1996 says: "The ... major possible adverse effects of chronic, heavy cannabis use ... remain to be confirmed"

"The major health and psychological effects of chronic cannabis use, especially daily use over many years, remain uncertain"

"As has been stressed ... there is uncertainty. ......To varying degrees....inferences from animal research, laboratory studies, and clinical observations about probable ill effects. In some cases inferences depend upon arguments from what is known about the adverse effects of other drugs, such as tobacco and alcohol".

"The probable and possible adverse health and psychological effects of cannabis need to be placed in comparative perspective to be fully appreciated".

The USA Merck Manual of Diagnosis and Therapy (1987) says:

"Cannabis can be used on an episodic but continual basis without evidence of social or psychic dysfunction. In many users the term dependence with its obvious connotations, probably is mis-applied... The chief opposition to the drug rests on a moral and political, and not toxicologic, foundation".

Jamaican Study 1970 :"... as a multipurpose plant, ganga is used medicinally, even by non-smokers. ....There were no indications of organic brain damage or chromosome damage among smokers and no significant clinical psychiatric, psychological or medical) differences between smokers and controls."

UK Royal Commission, The Wootton Report, UK, 1968: "Having reviewed all the material available to us we find ourselves in agreement with the conclusion reached by the Indian Hemp Drugs Commission appointed by the Government of India (1893-94) and the New York Mayor's Committee (1944 - LaGuardia) that the long-term consumption of cannabis in moderate doses has no harmful effects"

LaGuardia Commission Report, 1944" Cannabis smoking] does not lead directly to mental or physical deterioration... Those who have consumed marijuana for a period of years showed no mental or physical deterioration which may be attributed to the drug"

Panama Canal Zone Report, 1925"

There is no evidence... that any deleterious influence on the individual using [cannabis]"

Indian Hemp Drugs Commission, 1894

"The commission has come to the conclusion that the moderate use of hemp drugs is practically attended by no evil results at all. ... ...moderate use of hemp... appears to cause no appreciable physical injury of any kind,... no injurious effects on the mind... [and] no moral injury whatever."

see also:

Cannabis Prohibition - a very serious-crime

Cannabis - a safe medicine