The short term effects of a marijuana high are pretty well known. Says Scientific American: “Suddenly, the mundane seems hilarious, and ordinary foods taste delicious. People generally feel merry...athough undesirable effects—such as paranoia and irritability—are common as well.” What's much more of a black box is the long-term consequences of regular marijuana use.
As marijuana joins the medic's toolkit and Colorado and Washington work out the details of legal pot, it's fair to ask what impacts, good or bad, pot might have. Sorting through recent marijuana research, says journalist Virginia Hughes, has made her a little more tentative about the drug.
I bet the average Joe is much more likely to make jokes about weed than fret about its potential harms. I was in the joking camp last week. My perspective is beginning to shift, however, thanks to a new rat study suggesting that steady marijuana exposure causes brain and behavioral problems not only in the animals exposed, but in their future ratlets.
In rats, says Hughes, taking THC (the active ingredient in pot) makes those same rats more likely to use heroin. In humans, the idea that pot is a gateway to harder drugs has been around for a long time, even though we're still not really sure whether or not it's true. What had Hughes more concerned, she says, is a new study that showed that if adult rats use THC, their kids' brains will be affected in particular ways:
When those babies reached adulthood, even though they themselves had never been exposed to THC, their brains showed a range of molecular abnormalities. They had unusually low expression of the receptors for glutamate and dopamine, two important chemical messengers, in the striatum, a brain region involved in compulsive behaviors and the reward system. What’s more, brain cells in this region had abnormal firing patterns, the study found.
The offspring of THC-using rats were, like their parents, more likely to use heroin. They were also more likely to seek out novel experiences.
But humans have a level of agency—an ability to weigh decisions and make choices—that we just don't expect in rats. Our biology is a bit different, too.
The real problem with pot is just how little we really know. Marijuana, like LSD and heroin, is listed as a Schedule 1 drug by the U.S. Drug Enforcement Administration, a legal classification, says Scientific American in an editorial, that “thwart[s] legitimate research with marijuana.”