I really don't understand what the allure of cannabis is. For me, an immediate effect was a decline not only in cognitive ability but also short term memory. Like not being able to hold a thought for more than 5 seconds. How is that pleasurable? It should be no wonder long term use trends in the direction of decline. Of course, for older or termininally ill patients, the pain management benefits may be worth the trade-off, but if the choice is living with pain vs. being perpetually stoned, I think I'd try living with the pain as much as long as I can.
(FTR, I am not against legalisation, so no need to accuse me of trying to take away your drug. I just think we need to make these decisions with caution.)