12 de out de 2010

Why are the effects of marijuana so unpredictable? - Jonah Lehrer @wired.com

Alcohol is mostly predictable. When we drink a beer (or three), we usually have a pretty good sense of what it’s going to feel like. We can anticipate the buzz, the slackening of self-control, the impaired motor movements and the increased mind-wandering. In part, this is because alcohol is a tightly regulated psychoactive drug, and the alcohol content is clearly printed on every bottle. We also sense alcohol directly, so that the potency of a hard liquor tastes different than that of weak light beer. When we drink, we generally know how drunk we are going to be.

But not all drugs are so predictable. Consider marijuana, which can trigger dramatically different symptoms depending on the strain and context. It’s long been known that different strains of the drug contain various amounts of Tetrahydrocannabinol (THC), the main psychoactive ingredient. When people talk about the effects of the drug – such as giddiness, the munchies, and a sudden desire to watch The Big Lebowski – they’re typically referring to the effects of THC. (Interestingly, the same chemical can also make us paranoid. More on that later.) But THC doesn’t work alone – marijuana also contains cannabidiol, a compound associated with calm and relaxation. The ratio of THC to cannabidiol seems to be the key variable: Skunk-type strains, for instance, contain a higher ratio of THC to cannabidiol than, say, marijuana byproducts like hashish.

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