Cigarettes vs. Marijuana: Which is More Harmful?

Cannabis is the most commonly used recreational drug in the world, with an esimated 2.5% of people around the globe estimate it each year – and around 10.6% of the population in Australia consuming it at least once annually.

And with more and more countries giving the green light to medical marijuana, there has been an increasing focus on the potential health benefits of cannabis. But what about the risks for lung health – and how do they compare to smoking cigarettes?

The Thorax Study

Back in 2007, scientific journal Thorax published a study comparing the effects of smoking cannabis with smoking cigarettes.

Researchers compared the lung function and high-resolution CT scans of 75 cannabis-only smokers, 92 tobacco-only smokers, 81 non-smokers and 91 people who smoked both cannabis and tobacco. Those in the cannabis-only group smoked at least one joint per day, while those in the tobacco-only group smoked at least 20 cigarettes per day.

They found that while there was a ‘dose -response relationship between cannabis consumption and the degree of airways obstruction and hyperinflation,’ those who smoked cannabis alone were significantly less likely to develop chronic lung diseases such as emphysema.

In fact, just 1% of cannabis-only smokers developed the illness, compared to 16% of cannabis and tobacco smokers, and 19% of tobacco only smokers.

And while they found that chronic cannabis use is linked to certain adverse health illnesses, including bronchitis, psychotic illnesses, and some impaired lung function, there was less evidence to support a link between smoking cannabis and more serious illnesses such as lung cancer and birth defects in children.

In contrast, there is compelling evidence linking tobacco smoking with a long list of serious health problems.

However, researchers did find that smoking cannabis was linked to airway obstruction and hyperinflation – both of which are common signs of lung problems. They also found that a single joint of cannabis was equivalent to 2.5 cigarettes when lung function tests were carried out – and up to 6 cigarettes when airway function tests were conducted.

The Findings Explained

The fact that a single joint is significantly more harmful than a cigarette might seem at odds with the finding that cannabis smokers are much less likely to develop emphysema.

Dr Jonathon Foulds, a UK-based scientist who has spent considerable time studying the effects of smoking, says that the data can be explained by the different ways in which cannabis and tobacco are smoked:

‘A cannabis joint is typically smoked with greater intensity, with larger puff volumes and breath holding, leading to greater smoke and carbon-monoxide exposure than from a single cigarette (hence the greater impact on lung function on a per-smoke basis). However, while most regular cannabis smokers will smoke less than 5 joints per day, most regular cigarette smokers will typically smoke over 15 cigarettes per day. So the overall smoke exposure is typically much greater with tobacco than with cannabis and this is a likely reason for the greater occurrence of tobacco-caused illness.’

The findings can also be attributed to the fact that nicotine has a much shorter half-life than THC, which causes cigarette smokers to smoke more frequently. In addition, there is significant evidence to show that cannabis users typically stop using the drug before they hit middle age, while cigarette smoking is a lifelong habit for many. So under these ‘typical use’ conditions, cigarette smoking is much more harmful than cannabis smoking.

However, Dr Foulds is quick to remind us that, if the effects are compared on a ‘per smoke’ basis – i.e. if cannabis smokers smoked as often and as much as cigarette smokers – then cannabis would be much more harmful than cigarette smoking. This is what is meant by the ‘dose-response’ relationship.

Other Issues

While the study provides a useful comparison, it neglects to consider other factors, such as other ways in which cannabis can be consumed.

Cannabis is available in many different forms – it can be consumed in food, tinctures, or even vaporised. Studies show that these alternative forms of consumption are much less harmful than smoking it in a joint or a ‘cone,’ as they do not involve the combustion of materials.

The American Lung Association says that combustion of any material – whether it be marijuana or tobacco – is harmful and dangerous. The harm associated with smoking joints is therefore not unique to smoking cannabis, as smoke from wood, tobacco, marijuana or any other substance releases carcinogens; whereas the much longer list of adverse health effects associated with cigarette smoking is largely linked to the chemicals and harmful substances contained in cigarettes – including nicotine, butane, hexamine, methanol, ammonia, and acetone.

Cannabis users can therefore reduce the harm caused to their lungs by consuming cannabis in other forms – whether in liquid, food, or vaporised.

Studies suggest that vaporising cannabis reduces adverse effects – one study by the University of California found that ‘there was virtually no exposure to harmful combustion products using the vaporising device,’ while another study by Leiden University revealed that vaporisers were ‘safe and effective cannabinoid delivery systems.’

Based on these findings, it is difficult to understand why cannabis remains illegal in so many places when cigarettes are freely available.