Can marijuana cause cancer?

​

"Our findings suggest that occasional use of marijuana for these or other purposes may not be associated with adverse consequences on pulmonary function. On the other hand, our findings do suggest an accelerated decline in pulmonary function with heavier use – either very frequent use or frequent use over many years – and a resulting need for caution and moderation when marijuana use is considered..." - Mark J. Pletcher, MD, MPH 

http://medicalmarijuana.procon.org/