ATLANTA -- The Georgia Senate passed a medical marijuana bill Thursday, but supporters of cannabis oil say it represents a step backward from the landmark bill passed two years ago.

THC is the chemical that gives marijuana its psychotropic kick. It can also make cannabis oil effective at treating stubborn medical conditions, according to medical marijuana backers.

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"THC is an addictive drug," said Sen. William Ligon (R-Brunswick) during floor debate. Its detractors in the Senate say it’s also a danger – not only to its users but also to the state of Georgia.

Ligon warned that higher THC levels in cannabis oil could lead "toward the liberalization of marijuana laws and making it available for recreational use."

Georgia law now allows cannabis oil to have as much as five percent THC content. The bill in the Senate would roll that back to three percent. And some senators wanted to roll it back to one percent.

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"I don’t want to see it become like Colorado," said Sen. Ben Watson (R-Savannah), a sponsor of the 2017 bill. His bill also adds autism to the list of illnesses legally treatable with cannabis oil.

Colorado is a state where recreational marijuana is legal – and is frequently cited as a cautionary example by Georgia skeptics.

"We open up the door for its abuse and for people to abuse it and for people to be hurt and injured," Ligon cautioned.

In the end, the Senate voted to roll back legal THC content in cannabis oil from five percent to three percent.

As senators voted, state Rep. Allen Peake (R-Macon) watched from the wings. He sponsored the original medical marijuana bill in 2015 and is hoping for a chance to rewrite the Senate bill and restore the original seven percent THC threshold.

Medical marijuana backers are counting on it.

"I would say changing anything in the existing law and going backwards is unacceptable in the eyes of the parents," said Dale Jackson, who uses cannabis oil to treat the autism of his eight-year-old son Colin.