The law signed by Gov. Wolf on Sunday legalizing medical marijuana in Pennsylvania provides for an ambitious set of research programs to track how the drug works on the 17 health conditions listed in the law. But investigations are already underway, and the Pennsylvania Medical Society held a telephone conference Wednesday to discuss recent scientific findings.

Many doctors remain dubious of pot's health benefits and are wary of the politics driving legalization. But the evidence of its effectiveness in some conditions is slowly mounting.

Todd F. Barron, medical director of WellSpan Neurosciences in York, has been studying Epidiolex, a pharmaceutical-quality cannabis oil, in children with rare and hard-to-control types of epilepsy. Similar trials on the substance have been in progress at Children's Hospital of Philadelphia and New York University.

Epidiolex, made of purified cannibiodiol (CBD), was administered to 170 children suffering from Lennox-Gastaut syndrome.

In the group of 13 children studied in York, "across the board there was a 50 percent reduction in seizures," Barron said Wednesday. "Three were seizure-free."

About 1 in 10 children in the study reported mild to moderate side effects, which included sleepiness, lethargy, diarrhea, and vomiting, according to GW Pharmaceuticals, which published the results of the study last month.

Most of the children in the study have moved on from the double-blind, placebo-controlled stage to an open label trial in which both doctors and patients are aware of the treatment, Barron said.

At the University of Pennsylvania, Marcel Bonn-Miller is conducting the first placebo-controlled studies using different concentrations of cannabinoids to treat post-traumatic stress disorder.

Bonn-Miller said exposing patients to medical marijuana comes with risks. THC, which produces the sense of being high, carries the potential of being addictive and is known to increase anxiety.

But CBD, the second most studied compound in cannabis, is not addictive and has been shown to reduce anxiety, he said. His study, funded by the State of Colorado, will vary the amounts of THC and CBD to determine if cannabinoids can effectively treat PTSD, he said.

In a separate interview, Barron said he was approaching Pennsylvania's new law with caution.

"It's a case where the state has legislated medical care without real evidence," Barron said.

Patients whose epilepsy is newly diagnosed are already asking Barron if they should be treated with medical marijuana.

"The answer is no," Barron said.

"Medical marijuana should not be considered a first-line treatment," Barron said. "We already have lots of good drugs for epilepsy. Sixty to 80 percent we start on those become seizure-free."

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