Yes, in many cases it CAN kill you. This is because of a variety of problems with it.
For one, you are setting fire to a dried plant and inhaling the smoke into your lungs. This deposits tars, carcinogens and various chemicals directly into one of the most important organs of the human body. The lungs are DESIGNED to take chemicals out of the air such as oxygen and bring them into the blood system and to the brain. This is how nicotine and all these other mind altering substances work. They go from the air to the lungs and then are absorbed into the blood. Nice. This is also how various cancers and respiratory diseases of all kinds can get started. This is a slow way to die - but week definitely can help here.
The idiots who claim it is safer than cigarettes are morons with no science or medical background. Cigarettes have filters to stop a lot of the tar and crap. When was the last time you saw anyone smoking a joint with a filter? When was the last time you saw pot that was processed in a factory with any quality control? Dirt, poisons or any other sort of crap can be dropped right in there. Good luck with that. I swear - the people on here who smoke it the most should know better than to tell you otherwise.
Secondly, weed is often dipped, referred sometimes as wet, into all kinds of poisons and nasty other drugs. Even PCP is taken this way. PCP is a really messed up hallucinogen. It can drive a man to strip naked and throw himself through a window and then fight with ten cops until they break his arms and legs and handcuff him. Unless you grow your own drugs and watch it every second of the day from beginning to smoking - you cannot be sure the crap you smoke has not been dipped in some poison. They actually dip marijuana in poisons too because certain poisons will give you a reaction or kick or hit or high when burned and smoked. This makes you think the pot is better and you will want to pay more or buy more. Messed up I know. You are dealing with drug dealers you know. They don't give a rats rear end about your health.
Some people have died smoking weed dipped in various crap and there is very little you can do to stay safe.
Finally, when you smoke weed - you hang out with losers. Yes, the $hitbirds you go to school with who use drugs will generally grow up slowly if at all. They will end up coming home to live with mom and dad repeatedly. They will lack ambition. They will not excel in school or business. They will get in trouble with the law. They will have failed relationships. They will - AGAIN - be losers. Do you want to hang out with losers? Do you want to be successful in life or some joke of a stoner at best? Do you want to have kids some day who will grow up and want to smoke dope like mom and dad? Do you want to set such an example for kids? For your kids? Then why do it yourself.
Trust me - you hang out with losers too much and you will eventually get yourself into big trouble. You can be the nicest, smartest person there and still go down when they all get in trouble.
Do the right thing. You know it is right. Stay away from the idiots that are dumb enough to use any drugs. Stay away from alcohol before you are of age too. Even then-be an adult instead of a moron. So many kids get DUIs and lose their lives or licenses or worse - KILL SOME INNOCENT person on the sidewalk. All because they thought they would be cool.
Really - do the right thing and be responsible. You will be so thankful you did someday.
Proud Roman Catholic and father