On average, physicians in states where medical marijuana is legal prescribe fewer drugs, especially painkillers, than in other states. The implication is people who smoke pot have less need for painkillers or other prescription drugs.
Addiction to optoid painkillers, such as OxyContin, is a serious problem. Overuse of psychiatric drugs is another serious problem. Marijuana can be abused, too, but it is by far less dangerous.
One striking chart shows why pharma companies are fighting legal marijuana by Christopher Ingraham for The Washington Post. (Hat tip to Mike the Mad Biologist)