THC has been found to reduce the growth of common lung cancer tumors by 50 percent and significantly reduces the cancers ability to spread.
Opponents to cannabis usually disingenuously compare the best of todays samples with the worst of yesterdays samples rather than comparing the averages, and you can find contradicting numbers between the opponents.
"[pot is] 10 to 20 times stronger"
"In 1974, the average THC content of marijuana was less than 1 percent. But by 1999, potency averaged 7 percent."
"today's sinsemilla … averages 14 percent and ranges as high as 30 percent."
"The point is that the potency of available marijuana has not merely 'doubled,' but increased as much as 30 times."
- John P. Walters, White House Drug Czar
Some opponents will claim that THC content from samples in 1974 were 1% and todays potency is 30%. However cannabis with THC levels less than 1% is refered to as hemp or ditchweed, and is almost impossible to get high from.
The best strains could be up to 30% THC content mark but are extremely expensive and could have been around in the 1970's, it is just that the government never got its hands on any. Sinsemilla, cultivated cannabis where the female plants have not been pollinated, has had an average potency of 10% in the last decade, peaking in 1999 at 13%.
Plus higher potency cannabis is actually better for the users because less of it is needed to get the desired effect. If the method of consumption is smoking this means less smoke going into the lungs.
A study by Complutense University of Madrid in 2009 has found that THC effectively helps brain cancer cells eat themselves, causing the tumor to shrink. This process is known as autophagy.
An extensive scientific study in 2006 reported no significant link between smoking cannabis and lung cancer.
Whats more, THC has been found to reduce the growth of common lung cancer tumors by 50 percent and significantly reduces the cancers ability to spread.
Scientists believe that the cannabinoid THC may encourage programmed cell death or aptosis, to kill aging cells before they turn cancerous.