Just as vodka packs more of a punch than beer, a high-potency toke of cannabis — the name for the marijuana plant — delivers much more of the brain-active substance THC. That’s an abbreviation for tetrahydrocannabinol (TEH-trah-hy-drow-ka-NAB-ih-nol). It’s possible, [psychiatrist at King’s College London Tiago] Reis Marques says, that a bigger dose of THC simply may have stronger effects on the brain.
That’s important because as breeders have been improving their marijuana plants, THC levels have soared. Samples sold in Colorado, for instance, now have about three times as much THC as plants grown 30 years ago, a recent survey found.
People who reported using high-potency marijuana showed signs of damage in the corpus callosum . This is the major white matter tract that connects the left side of the brain to the right. Water molecules in the damaged corpus callosum diffused more easily than normal, a sign that its tissue had weakened.
This suggests a link between smoking high-potency pot and white-matter damage. But the study can’t prove that cannabis was to blame. “These people could have had deviant brain structures prior to use,” says Mitch Earleywine. He’s a psychologist of the University at Albany in New York.
