Here's some information I got about marijuana from an actual doctor.
Did you know that cigarettes are more harmful than pot? They are! The actual marijuana isn't dangerous, but there's one small problem:
When you go buy marijuana off the streets from a drug dealer, chances are it isn't JUST weed your getting. Drug dealers put other chemicals in the goods that make them very dangerous, one of these chemicals that is commonly added is rat poison.
Why do they add these harmful chemicals? Most likely because it makes it appear that there is MORE marijuana in the bag or whatever it is that it comes in.
So if marijuana isn't dangerous, why is it illegal? Well, we all know cigarettes aren't cheap, the government puts taxes on them, so they make a sh1t load of money with all the cigarettes people buy, so they won't ban cigarettes. Marijuana was never sold in stores, therefore no tax, therefore the government doesn't make any money. So they banned it.
In the end, if you can get some CLEAN marijuana, with no toxins/chemicals added to it, then you can smoke it with little risk at all, if any. The pot is actually therapeutic, it relaxes your muscles, and supposedly helps your memory. Which is why weed is actually prescribed by doctors for certain people with health problems.
