Some studies suggest that cannabinoids act as synaptic circuit breakers. “They can presumably put the brake on nerves that are firing abnormally,” said Dr Ware.

In this way, they have shown promise in the treatment of chronic constriction injury, sciatic nerve ligation, spinal cord injury, multiple sclerosis, cancer pain, osteoarthritis, visceral pain, muscle pain, inflammatory nociceptive pain, brachial plexus avulsion, trigeminal neuralgia, and neuropathy caused by HIV infection, said Dr Ware.

Cannabinoids might even help with some public health problems. One study (JAMA Intern Med. 2014;174:1668-1673) showed that states with laws legalizing medical marijuana had lower rates of mortality from opioid analgesics.

But they do come with risks. Short term, these are familiar: memory loss, impaired motor coordination, altered judgment and - in higher doses - paranoia and psychosis.

The longer-term adverse effects include symptoms of chronic bronchitis and increased risk for chronic psychosis in people with a predisposition to such disorders.

They also appear to alter brain development in children, affecting educational outcomes, lowering intelligence quotient, and diminishing life satisfaction and achievement.

“Alongside the fact that we’re looking at cannabis to use as therapy, we have be very careful we don’t spill that message over and tell kids that it’s okay to use when they’re very young,” said Dr Ware.

Cannabinoids are contraindicated in psychosis, unstable heart disease, and pregnancy, he said. And clinicians should watch out for patients with a history of legal issues or criminal charges.

It’s important to try to validate that the patient’s interest in the drug is for truly medical use, he added. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, the American Psychiatric Association describes a “cannabis use disorder” in terms similar to those used for the abuse of opioids, said Dr Ware.

Patients inclined to abuse might insist on a medical document for dried cannabis rather than trying other treatments. They might use the drug frequently, have trouble stopping, and be addicted to other substances. Friends or family might be concerned about their use, and it may affect their schooling, work, or social functioning.

“Use the opportunity when a patient is asking you about cannabis,” said Dr Ware. “Is she someone with cannabis disorder presenting as someone who is using it therapeutically?”

To understand better what patients might be helped, the province of Quebec, Canada, has launched a registry collecting data on patients who are prescribed marijuana, Dr Ware said.

And he is watching with interest how different states in the United States and nations around the world experiment with a variety of legal approaches.

“We’re at a very interesting time,” he concluded.

The APS has been working on a white paper to outline its position on cannabinoids, the society’s president, Gregory W. Terman, MD, PhD, told Medscape Medical News.

“I think people are opening their eyes to the possibilities,” he said.

Dr Ware’s talk illustrated the potential for using targets in the endo-cannabinoid system, he said. “I think most people agree that marijuana is not the way to go, and there may be cannabinoids that are more specific on pain with less effect on mental status.”

Dr Ware disclosed a research grant to his institution from CanniMed. Dr Terman has disclosed no relevant financial relationships.

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American Pain Society (APS) 34th Annual Scientific Meeting. Presented May 16, 2015.