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Does smoking cannabis cause cancer?

Does smoking cannabis cause cancer?
Whether or not cannabis causes cancer is a complicated question. We know from very clear evidence that tobacco causes cancer. But we are still learning about the effects of cannabis and whether it has the same effects as tobacco.
There are a number of factors that suggest cannabis may cause cancer;
The substances in cannabis smoke
Cannabis smoke contains the same cancer causing substances (carcinogens) as tobacco - at least 50 of them. In addition, cannabis is often mixed with tobacco when smoked.
One of these carcinogens is benzyprene. Benzyprene is in the tar of both tobacco and cannabis cigarettes. We know that benzyprene causes cancer. It alters a gene called p53, which is a tumour suppressor gene. We know that 3 out of 4 lung cancers (75%) occur in people who have faulty p53 genes. The p53 gene is also linked to many other cancers.
Cannabis also contains a substance called THC (tetrahydrocannabinol). It is the THC in the cannabis that changes your mood and behaviour. The amount of THC in a cannabis cigarette varies considerably. Researchers have shown that THC causes benzpyrene to promote the p53 gene to change.
The way people smoke cannabis
Substances in tar cause cancer. Cannabis cigarettes don’t have a filter, so more of the tar reaches the lungs. Also, people inhale cannabis smoke for longer than cigarette smoke. This is to get the full effect of the cannabis. But it means that the smoke is in contact with the lungs for longer.
Smokers’ lifestyles
Many people who smoke cannabis smoke tobacco cigarettes and drink alcohol too. Research evidence suggests that the combination of smoking tobacco, using cannabis and drinking alcohol can increase your risk of developing a cancer even further.
Evidence on cannabis and cancer
Several research studies have shown a link between cannabis and cancer. But other studies have shown no link. This makes it difficult to say exactly what the risk is. There have been a couple of systematic reviews that have tried to draw some conclusions on this.
In 2005 a review looked at the results of several studies into marijuana use and cancer risk. The researchers looked at 2 cohort studies and 14 case control studies. The case control studies involved many different types of cancer. Results were mixed and the researchers could not make any firm conclusions about the risk of cancer. It was also difficult to draw conclusions because of limitations in the studies. They included small numbers of people, involved too few heavy marijuana users and possibly underreported marijuana use in those countries where it is illegal.
In 2006 a systematic review looked at marijuana use and lung cancer risk. Although they could not find a significant link between marijuana and cancer, the reviewers reported that smoking marijuana increased tar exposure and caused changes to the lining of the small tubes in the lungs. They recommended that, until we have more definite evidence, doctors should warn people of the possible harmful effects of marijuana smoking. A New Zealand study in 2008 compared people with lung cancer to people who did not have lung cancer and found that regular cannabis use does increase the risk of lung cancer.
In early 2006 doctors reported on a possible link between cannabis and bladder cancer. Smoking is one of the main causes of bladder cancer. This study looked at men with bladder cancer under the age of 60, who had smoked marijuana, and compared them to men who hadn’t smoked it. The study showed that marijuana may be a possible cause of bladder cancer. But as the study was small, researchers need to investigate further to find out for certain.
So at the moment the evidence isn’t clear. We do know that, like tobacco, cannabis contains cancer causing substances. Therefore it would seem likely to increase cancer risk.
FAQs on smoking Cannabis;
Why researching cannabis is difficult? There are difficulties in researching the effects of cannabis since many people who smoke cannabis also smoke tobacco. And users of cannabis often mix it with tobacco. This can make it difficult to know whether it is the tobacco, the cannabis, or both that has caused a cancer.
The amount of THC in cannabis also varies. Some of the cannabis available today is much stronger than it was 20 years ago. These versions contain more THC.
Another difficulty researchers have is in recruiting people who smoke cannabis into studies. Because cannabis is an illegal drug in many countries, people may be reluctant to take part in research. And if they do agree to take part, they may not say how much cannabis they actually smoke.
What are some of the immediate effects of smoking marijuana? Some immediate physical effects of marijuana include a faster heartbeat and pulse rate, bloodshot eyes, and a dry mouth and throat. No scientific evidence indicates that marijuana improves hearing, eyesight, and skin sensitivity. Studies of marijuana's mental effects show that the drug can impair or reduce short-term memory, alter sense of time, and reduce ability to do things which require concentration, swift reactions, and coordination, such as driving a car or operating machinery.
Are there any other adverse reactions to marijuana? A common bad reaction to marijuana is the "acute panic anxiety reaction." People describe this reaction as an extreme fear of "losing control," which causes panic. The symptoms usually disappear in a few hours.
What about psychological dependence on marijuana?Long-term regular users of marijuana may become psychologically dependent. They may have a hard time limiting their use, they may need more of the drug to get the same effect, and they may develop problems with their jobs and personal relationships. The drug can become the most important aspect of their lives.
What are the dangers for young people? One major concern about marijuana is its possible effects on young people as they grow up. Research shows that the earlier people start using drugs, the more likely they are to go on to experiment with other drugs. In addition, when young people start using marijuana regularly, they often lose interest and are not motivated to do their schoolwork. The effects of marijuana can interfere with learning by impairing thinking, reading comprehension, and verbal and mathematical skills. Research shows that students do not remember what they have learned when they are "high".
Does marijuana affect the human reproductive system? Some research studies suggest that the use of marijuana during pregnancy may result in premature babies and in low birth weights. Studies of men and women may have a temporary loss of fertility. These findings suggest that marijuana may be especially harmful during adolescence, a period of rapid physical and sexual development.
How does marijuana affect the heart? Marijuana use increases the heart rate as much as 50 percent, depending on the amount of THC. It can cause chest pain in people who have a poor blood supply to the heart - and it produces these effects more rapidly than tobacco smoke does.
How does marijuana affect the lungs? Scientists believe that marijuana can be especially harmful to the lungs because users often inhale the unfiltered smoke deeply and hold it in their lungs as long as possible. Therefore, the smoke is in contact with lung tissues for long periods of time, which irritates the lungs and damages the way they work. Marijuana smoke contains some of the same ingredients in tobacco smoke that can cause emphysema and cancer. In addition, many marijuana users also smoke cigarettes; the combined effects of smoking these two substances create an increased health risk.
Can marijuana cause cancer? Marijuana smoke has been found to contain more cancer-causing agents than is found in tobacco smoke. Examination of human lung tissue that had been exposed to marijuana smoke over a long period of time in a laboratory showed cellular changes called metaplasia that are considered precancerous. In laboratory test, the tars from marijuana smoke have produced tumors when applied to animal skin. These studies suggest that it is likely that marijuana can cause cancer.

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