My eyes glaze over when people argue over the medical use of marijuana, because they're not always talking rationally. I can't help but think of the old adage, "Where there's smoke, there's fire."

And the debate is about to get hotter now that the Veteran's Administration is allowing vets to use medical marijuana in states where it's legal.

What a lot of us don't realize is that marijuana has been used as a therapeutic since ancient times. Chinese traditional medicine has used cannabis to relieve pain since the third century. It's also reflected in historical records of ancient Greece, India and the Islamic world.

In the western world, marijuana was also commonly used as a pain reliever until aspirin came along in the early twentieth century. Then in 1937, the US decided to ban the herb to prevent it from becoming a widely used recreational drug.

That didn't work so well. Today marijuana is a popular recreational drug and its medical use is growing. AIDS patients smoke it to control such symptoms as vomiting, insomnia, and weight loss. Others use it to help with glaucoma, movement disorders and neurologic-based pain.

Five compounds in marijuana are what make it a therapeutic. The main one is Tetrahydro-cannabinol, which has psychoactive effects that help a person relax. It's mildly analgesic and has antioxidant activity.

A second compound, Cannabidiol (kan-a-Ba-die-ol), is used to treat convulsion, inflammation, anxiety, and nausea.

Another compound, β-caryophyllene (cary-off-leen) has been shown to reduce tissue inflammation. And Sativex, an extract of cannabis, is used as an oral spray to treat multiple sclerosis.

Right now, medical marijuana is legal in fourteen states plus Washington D.C. In early 2011, New Jersey may be the 15th state to legalize medical marijuana.

Judging by this trend, medical marijuana may continue its run in history.