So here’s the very un-D.A.R.E. takeaway: Heavy marijuana use doesn’t seem to cause any sort of lasting brain damage. All the negative side-effects are relatively temporary. (But those side-effects are real.) Furthermore, the sort of anxiolytic giddiness triggered by THC comes with its own unexpected benefits, which is probably why humans have been self-medicating with cannabis for thousands of years.
I learned this from Super High Me, but it's nice to see it confirmed with a bit more scientific rigor.