If it is what tipped them over, then they shouldn't have been smoking in the first place. Anything can tip you over if you're emotionally unstable in the first place. Alcohol, gambling, relationships, etc.
Did they only use MJ and nothing else? I'm assuming so since you didn't say otherwise. No offense but just because your friends couldn't control themselves (I mean really... when it's time to stop it's time to stop, and one joint or occasional use will not mess you up) doesn't mean it should ruin it for the rest of us. Don't smoke it everyday multiple times for weeks in a row and you wont get lazy or depressed or grow boobs. Restraint. If you feel you need it to be happy or get through the day, it's time to stop altogether.
My opinion is legalize everything in small amounts like Mexico did. People need to learn some restraint. Take meth for example. Is using it everynow and then bad? say once or twice a year? Not in my opinion. If you do it once and then want more of it the next day, don't do it again. That's when it's easy to nip addiction in the bud is the first time you crave more. Look at me. I'm fine. Don't do it anymore, though. Sometimes I want it but i've already made a decision not to do it again. The cravings only last like 10 minutes for me. Lots of other things to do that aren't addictive. And don't use for the wrong reasons. Perfect example is my friend said she wanted to go on an Ice diet to lose weight fast. Now she's addicted because she wasn't responsible. I have no sympathy for her and her stupidity. I don't talk no her anymore. My other friend is an addict because he used to numb the pain of being molested by his ice-head dad when he was little. Both of his parents use. I do have sympathy for him because he was born into it and started using at a young age before he knew better. Now he's a huge addict that looks like a skeleton who lives in a trailer with his uncle and cousin. His uncle is a cook. I auctually hope his uncle gets arrested for feeding Josh poison. I do feel bad for him. Then again, Josh used to be my dealer so I suppose i'm partly to blame for enabling him by giving him money. I always had a love/hate feeling towards josh. He's so stupid and his brain is so fried you can't stay mad at him. He's like a child. Like anna nicole.
Another one of my fried ex-friends put hydrocodone in the teachers coffee and was arrested and expelled. I have no sympathy for her stupidity. She got what she deserved. The teacher was allergic (or said she was) and apparently almost died from what i've heard. Lol, funny thing is her son was one of my ice-head friends. He's now recovered (as much as you can be I suppose). We both quit going to NA at about the same time, it was just stupid and we didn't buy into the BS. We're both fine without the 12 steps, but according to them without it we are on a downward slope lol. I feel that the 12 steps just replaces one addiction with another. Dope is replaced by a lifetime of dependance on an imaginary (in my opinion) higherpower and meetings where they chain smoke and drink coffee and tell you what an addict you are. Then when their probation is over they relapse.
One person I knew, the girlfriend of a guy I hate, took too many skittles at school and thought her legs were floating away. She got in LOTS of trouble. She was stupid for taking too much AND taking the wrong drug, a dissasociative to boot, at school.
Look at E. Will it kill some brain cells the first time? yeah. Killing a few is no problem. Even alcohol kills brain cells. Just don't do E all the time. Maybe a few times a year. Don't do too much either and watch your water intake you'll be fine.
To me, this is the difference between use and abuse.