Though there is some evidence out there to support the claim of tolerance. It is possible, theoretically, to build up a tolerance to THC, but it's temporary if anything.

The reason you don't get high the first time you smoke (only some people, mind you. I got FACED the first time I smoked, so...) is because it's difficult to really Get high. Allow me to explain..

When you smoke, you have to realize you're high. You don;t really see it all of a sudden, because it's a mental change. THC is an agonist- it mimics the neurotransmitters your brain already produces. The high occurs gradually, and it's a change of state-of-mind. The human brain does it's best to accomodate and adjust to anything it experiences. So, when you smoke, your brain tries to remain normal. You don't suddenly FEEL high. You have to kind of look for it, introspectively, and you'll REALIZE you're high.

So, by my calculations.. You DID get high the first two times you smoked, you just didn't realize it. If your mom wants to smoke, she will. If it will help her (which it will), then tell her that. show her the evidence. but don't force her to, if she doesn't want to, man. Not cool

I could be DRASTICALLY wrong on all this. I just got off 10 hours of waitering, and I'm high as a MOFO. But whatever.