I think that there has never been a marijuana related overdose death ever. I think marijuana is a gate way drug just like alcohol is. I think cigarettes are probably worse for someone medically then marijuana. I think marijuana has medical uses (getting people to eat who are undergoing chemo as an example and helping with their nausea).
Yes marijuana can be abused and effect peoples decision making which can lead to death. Yes the drug cartels kill over marijuana and it may or may not effect people commiting suicide.
Alot of the same concerns can be applied to alcohol. When alcohol was banned the Mafia (think drug cartels) made a lot of money with illegal alcohol. When they made alcohol legal again the mafias lost their role in the alcohol business.
I guess I just dont see why marijuana is illegal when drinking causes more deaths from overdose, drinking and driving, abuse, and the list goes on with the exception of drug cartels in other countries. But that would go down if marijuana were legalized. Hell the government could take all the confiscated marijuana and store it and test it for safety then legalize it and sell all that stored marijuana and actually make some money.