There are many studies that report on the harmful health effects of smoking tobacco, such as cancer, respiratory disease (bronchitis, emphysema and asthma) and heart disease. While there have been few studies conducted on the effects of cannabis smoke, there is growing evidence that there are similar major health concerns for those who smoke cannabis.

Tobacco and cannabis smoke both contain harmful chemicals which are absorbed when inhaled. This exposes the smoker’s lungs to greater risks of developing major respiratory diseases and/ or cancer.

What are the links between smoking tobacco and cannabis?

International reports have found specific links between smoking both tobacco and cannabis, such as:

• many people who try cannabis have previously smoked tobacco
• many current cannabis smokers are also current cigarette smokers
• early onset of tobacco use may act as a ‘gateway’ to future cannabis use
• nicotine dependence can develop if tobacco is used in combination with cannabis
• smoking both cannabis and tobacco increases health risks rather than smoking each alone

Are there any differences in smoking cannabis versus tobacco?

Tobacco is usually smoked in tailor-made or ‘roll your own’ cigarettes, while cannabis is smoked in a variety of ways, such as:

• a pipe with/without tobacco
• a joint ‘roll your own’ cigarette with a long cardboard tip, with/without tobacco
• a bong (water pipe) or bucket bong with/without tobacco

The most harmful way of smoking cannabis is through a bong. Inhaling smoke through water makes it cooler, which makes it easier for the smoker to inhale a greater volume of smoke more deeply into the lungs. This increases the surface area for tar and other carcinogens to affect the respiratory system.

Mixing tobacco with cannabis is polydrug use. Nicotine is an addictive drug and the combination of these two substances increases exposure to tar and other carcinogens, causing greater risks to the lungs, respiratory organs as well as the cardiovascular system.

Cannabis smokers are also at risk of developing nicotine dependence if they mix tobacco with their cannabis.

Compared to tobacco cigarette smokers, people who smoke cannabis typically:

• inhale more smoke (two-thirds larger puff volume)
• inhale the smoke deeper into the lungs (one-third greater depth of inhalation)
• hold the smoke in the lungs for longer time periods (up to four times longer)

This results in the lungs being exposed to:

• greater amounts of carbon monoxide and other smoke irritants
• greater retention of tar in the respiratory tract

Both carbon monoxide and tar increase the risks of a range of health problems including respiratory tract infections, bronchitis and lung cancer.