Your friend that only smokes pure indica because sativa 'makes them paranoid?' Scientists have confirmed your sneaking suspicion that these dopers are just blowing smoke.

As any serious toker will point out, cannabis is among the planet's oldest cultivated crops. But driven underground, marijuana growth has been a genetic free-for-all, with cross-breeding mixing up even the most basic distinction — between indica and sativa — that many hold dear.

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That's all according to a new study from a pair of Canadian scientists published in the peer-reviewed journal PLOS ONE. As the paper's author, Sean Myles, an agricultural geneticist at Dalhousie University in Nova Scotia, tells Wired, "They’re not totally wrong, but the split [between indica and sativa] is nowhere near as accurate as you’d need to be in another horticultural crop with a formal classification system.”

From the paper:

Although the taxonomic separation of the putative taxa C. sativa and C. indica remains controversial, a vernacular taxonomy that distinguishes between “Sativa” and “Indica” strains is widespread in the marijuana community.

Sativa-type plants, tall with narrow leaves, are widely believed to produce marijuana with a stimulating, cerebral psychoactive effect while Indica-type plants, short with wide leaves, are reported to produce marijuana that is sedative and relaxing.

C. sativa and C. indica may represent distinguishable pools of genetic diversity, but that breeding has resulted in considerable admixture between the two.

In testing, for example, Jamaican Lambs Bread, reported as 100% sativa, was "nearly identical" to a reported 100% indica strain from Afghanistan. Sample mix up or mislabeling, of course, is a possibility.

The paper also points to the rise of hybrid as a designation, with indica or sativa cited as "dominant" in a particular strain. That can be helpful, but it's likely that all hybrids are really, really hybrid.

“From an industry standpoint, there have been moves towards developing more consistency,” Taylor West, the deputy director of the National Cannabis Industry Association, tells Wired. “There’s no real centralized information, so it’s difficult for people to tell one strain of Strawberry Kush from the next.”

So now you know what to tell your friend who prefers a pure indica Blue Dream. "You're high, man."

Related: Pot Smokers Getting Up Early Saturday For 4.20-Mile Footrace