Well using amphetamines will certainly motivate one to do /something/ :P The rampant use of prescription amphetamines while speed and meth remain much maligned

Well using amphetamines will certainly motivate one to do /something/ :P The rampant use of prescription amphetamines while speed and meth remain much maligned is another issue entirely. I also know many counter-examples, but most people I know that have used cannabis regularly for years or decades seem to sort of auto-regulate their use. It waxes and wanes - sometimes daily, sometimes monthly. I don't suspect that it has extremely negative effects, but it wouldn't surprise me if their were a mix of effects that occur with heavy and regular use that don't occur with more moderate use. To each their own -- I also know highly functional regular opiate users, and some who have fallen off the functional boat hard. I'm all about harm reduction and personal freedom when it comes to altering ones consciousness. Also, of course we know that probably the most toxic substance to use heavily and regularly is alcohol. I expect many orders of magnitude more harmful for both the brain and body than cannabis will ever be shown to be.