While opioid pain relievers offer critical benefits to certain patients, such as those with cancer-related pain, the rise of opioid prescriptions has had devastating public health consequences. The C.D.C. recently urged physicians to be very cautious in prescribing these drugs.

Meanwhile, access to medical marijuana has expanded rapidly - 24 states and D.C. have legalized its broad medical use - and chronic or severe pain is the most common condition reported among those using it. On it's face, this might seem to mirror the rise in prescription opioid use.

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