There is no plant in the history of human existence with as checkered a reputation as cannabis. It is either a heaven-sent cure for all that ails us, or it's a scourge on society on par with the Black Death.

Sussing out truth from fiction when it comes to marijuana is no easy undertaking, but after two years of intensive research related to the publication of my new book Pot Inc. [Sterling, $22.95], I can say with certainty that there are several old myths that can be put to rest for good (or at least put into context).

And no, I'm not talking about the old canards that smoking pot can make you gay or turn you into an ax murderer. I'm talking about those more lingering concerns that Nancy Reagan fretted about and which, despite quantum leaps in scientific knowledge and medical research, President Obama's Administration hopes you will too.

This information is important because, despite his campaign promises prior to the 2008 election, in which he said federal resources shouldn't be wasted busting medical marijuana patients and the state-compliant businesses that serve them, Obama has lately been embarked on a medical marijuana crackdown that Rolling Stone reported is on pace to go beyond George W. Bush's undertaking. Leaders in his administration routinely deny that marijuana can be medicinal and have reverted back to the Reagan-era fear mongering about how any slip in the public's perception of its harm poses a grave threat to the nation's youths.

But it's precisely because of medical marijuana laws that are now in place in 16 states and Washington D.C. that more accurate knowledge of marijuana's relative risks and benefits are becoming more widely known. Think what you will about these often vague and easy to abuse laws; if nothing else, they've raised the level of debate in this country about a substance that has been maligned and vilified for more than seventy years, for no good reason.

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