Is marijuana less dangerous than alcohol, as Barack Obama claims?

Updated

Legalisation of marijuana is back in the news. In the United States, Colorado and Washington have legalised the sale of marijuana for recreational use. In Australia, some have called for the legalisation of marijuana as a solution to alcohol-fuelled violence in popular nightspots.

US president Barack Obama weighed into the debate in a recent magazine interview. The president told the reporter: "As has been well documented, I smoked pot as a kid, and I view it as a bad habit and a vice, not very different from the cigarettes that I smoked as a young person up through a big chunk of my adult life."

"I don't think it is more dangerous than alcohol," he said.

When asked whether it was less dangerous, Mr Obama said that it was less dangerous in terms of its impact on the individual consumer. "It's not something I encourage, and I've told my daughters I think it's a bad idea, a waste of time, not very healthy," he said.

The claim: Barack Obama says smoking marijuana is less dangerous than drinking alcohol.

Barack Obama says smoking marijuana is less dangerous than drinking alcohol. The verdict: There is not enough evidence to substantiate Mr Obama's claim.

ABC Fact Check looks at whether Mr Obama's comparison of the health effects of marijuana and alcohol is supported by the evidence. In light of Mr Obama's second answer, the analysis is confined to the direct health impact of these substances on the user.

How are alcohol and marijuana used?

The health risks associated with both substances increase with quantity and frequency of use and, in relation to marijuana, the age of first use.

The Australian Institute of Health and Welfare conducts a survey of alcohol and drug use by Australians and then makes an estimate of use by the wider population.

Its most recent report estimates that in 2010, of the population aged 14 years or over, 80.5 per cent had used alcohol and 10.3 per cent had used cannabis in the last 12 months.

The figures for the consumption of alcohol are broken down into "drinking status". The institute estimates that of all people aged 14 years and older:

7.2 per cent drank alcohol daily

39.5 per cent drank weekly

33.8 per cent less than weekly

7.4 per cent were ex-drinkers

12.1 per cent had never had a full glass of alcohol

The incidence of daily drinking increases with age, with the highest portion being among people aged 70 and above (14.8 per cent) and the lowest being 2.1 per cent of people aged 20 to 29. Reliable figures are not available for the age range 12 to 19.

The survey found that of people aged 12 years and older who had used cannabis in the last 12 months:

13.0 per cent used every day

20.9 per cent once a week or more

13.5 per cent about once a month

17.9 per cent every few months

34.6 per cent once or twice a year

Professor Wayne Hall of the University of Queensland tells Fact Check that "given the illegality of cannabis and the lack of standard doses or methods of use, it is difficult to quantify how much cannabis users typically use." He estimates about one in 10 people who use cannabis will be heavy users - that is, using daily or almost daily.

Health impact of alcohol

Many alcohol users will have at one point in their lives experienced some of the short term effects of too much alcohol such as headaches, lack of coordination, shakiness, nausea, vomiting and passing out.

More serious impacts of long term and excessive alcohol consumption include brain damage, heart and liver disease, pancreatitis, mouth, neck and throat cancers and a compromised immune system. Long term alcohol use can lead to dependence, with severe withdrawal symptoms.

Guidelines released by the Australian National Health and Medical Research Council say there is "no level of drinking alcohol that can be guaranteed to be completely safe or no risk", but its advice is that the health risks can be reduced if people "drink no more than two drinks per day".

The US National Institute on Alcohol Abuse and Alcoholism allows for slightly higher consumption. It says that "low-risk" drinking levels for men are no more than four drinks on any single day and no more than 14 drinks per week. For women, "low-risk" drinking levels are no more than three drinks on any single day and no more than seven drinks per week.

Health impact of marijuana

Like alcohol, marijuana is not a harmless drug. The Australian Drug Foundation notes that in addition to the desired effects on users, "low to moderate doses of cannabis" can also lead to increased heart rate, low blood pressure and anxiety. Over the long term, cannabis can have a negative impact on brain and lung function, hormone levels, the immune system and mental health.

"Cannabis use is associated with psychotic symptoms, schizophrenia, anxiety and depression," according to a discussion paper released by the United Nations Office on Drugs and Crime. The paper also notes that "long-term heavy cannabis users... show impairments in memory and attention that endure beyond the period of intoxication and worsen with increasing years of regular cannabis use."

Dr Scott Smid of the University of Adelaide tells Fact Check that "in those predisposed to certain types of mental illness, marijuana consumption may worsen their conditions". In particular, he notes that studies have shown that cannabis use can double the chance of developing schizophrenia in those already vulnerable to the illness and can "bring on a first episode by a year or more depending on age at first use".

Less discussed is the connection between cannabis use and cancer. Dr Smid tells Fact Check that "there is evidence that marijuana consumption via smoking increases lung cancer risk [and] possibly other cancers as well". The British Lung Foundation has noted that cannabis smoke has the "same carcinogens as tobacco smoke". However, it says cannabis smokers inhale "four times more tar" and retain "one third more tar in the respiratory tract". It says this is because users inhale more deeply and hold the smoke in for longer.

The foundation referred to a 2008 study which found that "smoking one cannabis cigarette a day for one year increases the risk of lung cancer by 8 per cent" which is more than the 7 per cent increase caused by "smoking one pack of tobacco cigarettes (20 cigarettes) a day for one year".

Professor Wayne Hall of the University of Queensland and Professor Louisa Degenhardt of the University of New South Wales also noted in a medical journal article that "regular cannabis smokers report more symptoms of chronic bronchitis (wheeze, sputum production, and chronic coughs) than do non-smokers", although this could be a consequence of marijuana users also smoking tobacco.

Which one is worse?

Even health experts struggle to make a meaningful general comparison between the health effects of alcohol and cannabis.

Experts contacted by Fact Check tend to specialise in looking at marijuana or alcohol, and there are few academic studies making a direct comparison between the harms of the two substances. A further difficulty is that people consume the substances in different quantities and patterns. Sourcing satisfactory data on cannabis use and its health effects is hindered by the fact that the drug is illegal in many countries.

Professor Robin Room, director of the Centre for Alcohol Policy Research at Turning Point Alcohol & Drug Centre, tells Fact Check that while there are "risk calculations for different levels and frequencies of drinking... no such calculation has been done to my knowledge for cannabis - nor could easily be done".

Dr Smid tells Fact Check: "It doesn't make much sense to compare the two because they are very different drugs that are used in lots of different contexts."

In relation to cannabis, Professor Hall tells Fact Check that "the evidence for harm arising from cannabis use is clearest for those who engage in daily or near daily use". However, it is harder to make a call when looking at more irregular use. "We still argue about the risks and alleged benefits of using small quantities of alcohol where we have extensive epidemiological data," he said. "We have less capacity to give evidence-informed advice on the risks of less than daily cannabis use."

Professor Room says that "at the lower end... it would be hard to say which was riskier". However, he tells Fact Check that at "higher levels both in the moment and cumulatively over time, clearly alcohol is riskier".

The verdict

There is not enough evidence to assess whether marijuana is less dangerous than alcohol for users.

Mr Obama's comparison between the health effects of alcohol and marijuana is unsubstantiated.

Sources

Topics: obama-barack, cannabis, drug-use, alcohol, health, mental-health, lung-cancer, liver-and-kidneys, world-politics, drugs-and-substance-abuse, australia, united-states

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