Marijuana and cancer

Does marijuana cause cancer? This is an issue which has received a great deal of attention but is not an easy question to answer.

It is claimed that smoking marijuana increases the risk of lung cancer. That there is a link between the two but this is not conclusive.

Conversely, there are claims being made for the anti-cancer properties of marijuana. There is a growing interest in the idea of ‘medical marijuana’ which is said to have therapeutic qualities that may ease several conditions.

Plus some researchers claim that certain chemicals present in marijuana, for example tetrahydrocannabinol (THC) may kill off cancerous cells. Examples of these include brain cancer and prostate cancer cells.

Effects of marijuana smoke

There is a risk if marijuana is smoked. A popular way of suing marijuana is to add it to tobacco and smoke it as a cigarette (or a ‘joint’).

Whilst we are unsure if marijuana is directly responsible for cancer what we do know is that there is a link between tobacco and cancer.

There are numerous health risks associated with tobacco smoking which include cancer. Tobacco contains thousands of chemicals, many of which are toxic and some which are carcinogenic.

Carcinogenic means cancer causing.

Examples of these substances include:

• Tar (carcinogenic)
• Benzpyrene (carcinogenic)
• Nicotine
• Ammonia
• Carbon monoxide
• Hydrogen cyanide

Nicotine is the substance which is responsible for causing an addiction.

But marijuana smoke contains many of the same substances as tobacco smoke which also includes carcinogens. One example of this is benzpyrene.

Benzpyrene

This is a hydrocarbon which is also a known carcinogen that is present in both tobacco and marijuana smoke, and coal tar.

It works by altering the structure of a gene called ‘p53’which acts as a tumour suppressant. A tumour suppressant works by preventing uncontrollable cell division which causes cancer.

The p53 gene is linked to several cancers.

(Source: Cancer Research UK)

THC and cancer

Marijuana smoke contains the primary chemical THC or ‘tetrahydrocannabinol’which is responsible for the ‘high’that people experience when they use marijuana.

Some studies state that this chemical ‘switches off’the p53 gene which allows cells to multiply and results in cancer.

But other studies show that THC is effective against brain tumour cells and possibly other cancers as well.

However these results were obtained from a laboratory study in which pure samples were used rather than analysing the effects from smoking marijuana.

Methods of smoking marijuana

Many people who smoke marijuana do so in a different way to smoking a cigarette. They tend to inhale deeply and for longer to experience all the effects but this also increases the length of time the lungs are exposed to this smoke.

Marijuana cigarettes or ‘joints’ do not have filters which mean that a greater amount of tar present in the smoke reaches the lungs. Plus tar contains carcinogens which increases the risk of cancer.

There are a greater percentage of carcinogens in marijuana smoke compared to tobacco smoke.

This risk is increased further if this is combined with excess alcohol consumption and tobacco smoking.

Is there an increased risk of cancer?

There are other factors which may cause cancer apart from marijuana.

Tobacco is a risk factor for cancer so it may be safe to say that lung cancer or head and neck cancers are more likely to occur as a result of this rather than through smoking marijuana.

In other words, it is the tobacco which causes cancer and not marijuana.

Marijuana does have a negative effect on the lungs, increasing the risk of infections and diseases, and causing a blockage within the airways.

Whilst this is not a direct cause of cancer it is as well to be aware of this damage in the lungs and any possible long term effects.

What has also to be taken into account is the number of users who smoke marijuana via a bong (with no tobacco), brew it in tea or add it to food.

Not everyone who uses marijuana smokes it with tobacco.

So, cancer may be caused by marijuana, marijuana mixed with tobacco or tobacco only. Further research is needed to determine if there is a link between marijuana and cancer or not.