What causes tolerance and how can you lower you tolerance towards cannabis. obviously taking a break from smoking is a great way to do it also switching up the strains you smoke but how log do you have to take the break for. no research shows that cannabis is out of your system within 11 days not the 30 days once believed so does that mean a 11 day break will bring your tolerance down to base line levels. i understand that their is a psychological aspect to this as when you first smoked marijuana the experience was more extreme but as you become accustomed the the experience it becomes less extreme this is a tolerance build up absent biological factors. for those of you with a degree in biochem what is it that causes your tolerance to increase. also i read some time back on a site that a vitamin supplement such as b12 (could have been something else) helps to lower or rather resist increases in tolerance.