This has been known for years. It's also been known that cannabinoids have a protective effect against developing certain types of cancerous tumors.
Cannabis and Cannabinoids (PDQ®) - National Cancer Institute
I can't find it right now, but there was a multi-year study performed on rats back in the 70's that showed high-levels of thc and other cannabinoids were able to shrink, and in some cases kill, cancerous tumors.
In a real scientific atmosphere, research would have progressed further and thc would have ultimately been tested on humans with cancer. But further research was denied because all Schedule I drug research has to be approved by federal authorities. In reality, it's easier to get approval to run cocaine studies than it is to conduct research on marijuana.
All of these studies have continued to be buried for various reasons, be they they war on drugs, the desire to keep marijuana and therefore hemp timber from threatening the lumber and combustible fuel industries, or big pharma throwing money around to keep the studies buried.
As someone who spent the better part of a decade helping to develop big pharma drugs, I can say for certain that this happens and marijuana legalization/reclassification is a large concern for drug companies, primarily because you can't patent a naturally occurring plant.
I support legalizing, but unlike others, I'm not inclined to believe it will happen for at least a few decades, if ever. What I have an absolute problem with is how marijuana is classified as a drug with no medicinal benefits when virtually every piece of research that uses an empirical approach to the scientific method says otherwise.
I'm not one of the crackpots around here that thinks the FDA needs to be done away with (still love you crackpots though, you guys know who you are :action-smiley-027

. I've seen firsthand the effects that most drugs in development have, and it isn't pretty (things like necrotic skin, enlarged and necrotic organs, hallucinations, floating limb syndrome, self-injurious behaviors, etc.). Luckily, the vast majority of them are shelved relatively early in development because the manufacturers know the results from the toxicology testing in animals will lead to the FDA rejecting the drugs.
But by the time drugs get to the first round of FDA approval and prior to moving to clinical trials, the drug company has already spent hundreds of millions, if not billions of dollars developing and testing. A few unwanted side-effects in a small percentage of the population isn't going to stop them from taking it to market if it wasn't for the FDA denying approval. The possibility of a couple of wrongful death lawsuits where they have to pay out maybe hundreds of millions of dollars isn't enough to outweigh the profits they'll make during the time they hold an exclusive patent on a popular drug*.
That being said, there is corruption of the highest levels within that organization and from outside pressures that make a complete overhaul of the FDA necessary. That corruption is one of the reasons that a drug like Paxil gets approved when it probably should have been killed off by the time it made it to testing in non-human primates (typically the last step before initial trials in humans).
Corruption and political pressure is also why something like marijuana is classified as being just as harmful and addictive as heroin, as well as having no medicinal value. Even though virtually all legitimate scientific research says otherwise.
/:angrysoapbox_sml:
* Might as well get this out of the way before the "free market" and "it was their choice to take it" bullshit.
This is not an free market issue. It's a truth in advertising/public safety issue.
Without the FDA approval regulations and procedures, even most of you smart motherfuckers wouldn't have a clue how to determine the safety or effectiveness of a drug. And I do mean that about the smart mo-fos here, because quite a few of you are highly intelligent, or can at least seem to be.
Even if you were able to accurately decipher the reports, and therefore the safety and potential risks of the drugs, the only way you could tell with relative certainty would be to look at toxicology and efficacy reports from all stages of development. Most early stage research is proprietary and not available to the public, and not something these companies would ever divulge because results from one drug study often give clues to future development plans.
Clinical trials in humans are easier to get your hands on, but even then there is the risk that the cohorts involved in the clinical trials weren't representative of at-risk populations.
In short, anytime you put a drug into your body it's a crap shoot, but FDA regulations, and the equivalent bodies in other countries, are the best chance that you have of not taking something for a headache that ends up giving you a heart attack.
And no, you're doctor probably doesn't know much more than you do about any of it. Doctors that write prescriptions are not scientists and they aren't scientific researchers; they're healers and diagnosticians. Yes, they'll have a better understanding of how the drug works within your body, but for the most part, they rely on the information provided by the drug companies and pharma reps that get them to use the drugs.
Without FDA regulations there is no reason for a drug company, specifically a new one that needs to turn a quick profit, to perform the research and testing needed to prove efficacy and safety. And there's even less of a reason for them to market their product in an ethical manner. It's hard enough getting them to do that now.