ST. PETERSBURG, Fla. -

Cannabis has been used for medicinal purposes for thousands of years, yet it’s still a controversial topic in the U.S.

Under federal law, only FDA approved medications can be prescribed; marijuana is not one of them. Still medical marijuana is now legal in 20 states, plus our nation’s capital. So is marijuana really medicine?

Gretta used to suffer with seizures, having up to three a day as a child.

“It’s scary because anything could happen to you,” Gretta said.

She took prescription medication, but it had nasty side effects like liver spots, severe headaches, and bleeding gums.

“I could eat a piece of bread and my gums would start bleeding,” Greta added.

Then, three years ago she lost her insurance and turned to marijuana.

“I have not had a seizure since,” Gretta said.

She also hasn’t had any side effects. The account interests Dr. Eduardo Locatelli. He’s had 20 epilepsy patients tell him they’ve used cannabis this year, even though it’s illegal where he practices.

“I can tell you it’s not making the epilepsy patients worse, but I need to answer the other question, does it make it better?” said Locatelli, director of the Neuroscience Institute and director of the Epilepsy Program at Holy Cross Hospital in Fort Lauderdale.

Dr. Shirley Zelikovsky believes it may. She sees patients with terminal illnesses and chronic pain.

“They’ve told me that it just makes them feel better, and it reduces the need to take the other medications,” said Zelikovsky, who's a family medicine physician with Bethesda Health City in Boynton Beach.

It is something Richard Corso is worried about. His back pain is so severe he’s on hospice level pain pills.

“If you make a mistake with that, you don’t get another chance. You die,” Corso said.

The CDC has no reports of marijuana-induced deaths, but every 19 minutes someone dies of a prescription overdose.

“You can’t overdose on marijuana, but you can on the other drugs,” Zelikovsky said.

And get this; recent studies show opioid drugs used to relieve pain in cancer patients may stimulate the growth and spread of tumors.

However, experts from the UK say that the cannabis plant has been used to treat everything from cancer and glaucoma to Crohn’s disease and multiple sclerosis.

Even so, a consultant for the Drug Free America Foundation says smoking the drug is not the answer.

“My concern is there’s going to be no control whatsoever on the use of the marijuana on the way it is now,” said David A Gross, special advisor to Drug Free America Foundation and editor in chief of the Journal of Drug Policy and Practice.

Possible side effects could include impaired memory, anxiety, lung damage, and weakening of the immune system.