Medical use of cannabis is officially accepted -- and is helping to limit opioid abuse.

Drug abuse is devastating American society. Opioid overdose alone killed more than 33,000 people in 2015. But rather than address this public-health crisis, Attorney General Jeff Sessions has declared a new war on drugs. He has re-introduced mandatory minimum sentences for drug crimes and has asked Congress to let him spend money to prosecute people and businesses behaving in accordance with their states' medical marijuana laws.

Clearly, Sessions is out of step with the scientific consensus regarding the medical effectiveness of cannabis.

Because cannabis remains classified as a Schedule I drug under the Controlled Substances Act, all uses of it are illegal under federal law. People who use it to treat a variety of medical conditions risk arrest and prosecution. In light of the medical evidence this makes little sense.

Consider that drugs designated Schedule I are supposed to have “no currently accepted medical use.” Yet in January, a pathbreaking review by the National Academies of Sciences of more than 10,000 peer-reviewed studies found “conclusive” evidence that cannabis (whether it's the whole plant or an extract) is clinically effective at treating a number of illnesses, including chronic pain. The National Institute on Drug Abuse has likewise acknowledged the evidence for the drug's clinical efficacy.

What's more, the clinical use of cannabis stands to bring significant budgetary savings for government health insurance programs. Research that we've recently published in Health Affairs shows that if all 50 states allowed medical cannabis in 2014, Medicareand Medicaid would have saved more than $1.5 billion on prescription drugs.

The biggest savings would come from reduced prescriptions for pain medications -- a large share of which are opioids. This explains why states that have approved medical cannabis have experienced fewer opioid-related deaths. As NIDA noted, “medical marijuana products may have a role in reducing the use of opioids needed to control pain.”

Note that other preliminary but growing evidence suggests cannabis might also help patients with chronic pain who are already fighting an opiate addiction.

Such evidence appears to have affected many people's thinking. Ninety-four percent of Americans, according to the most recent Quinnipiac poll on the subject, support the medical use of cannabis -- including 90 percent of Republicans. It's no wonder that 29 states have looked beyond the federal law and approved the medical use of whole-plant cannabis (with another handful approving the use of cannabis oil).

Ultimately, a war on cannabis would hurt patients who are already hurting. Maintaining the scheduling of cannabis, increasing marijuana arrests and re-instituting minimum sentences for possession would stand in the way of their doctors' expertise and oversight. Even in the states that allow the use of medical marijuana, as long as cannabis remains Schedule I, doctors can only recommend that patients in pain try cannabis instead of opioids and hope for the best. Written or formal follow-up, assistance with dosing, or integration with other aspects of care may still leave the physician in federal jeopardy.

The Trump administration should instead remove marijuana from Schedule I, and turn medical decisions on the use of cannabis over to patients and their physicians.