Pediatric neurology and neurology are different specialties in medicine because developing brains are very different from adult brains. I'm all for legalizing pot and it's just natural that young people _experiment_ with drugs. That does not mean that constant drug use during adolescence should be perceived as normal or harmless.
One example is in cholonergic neurons in the pre-frontal cortex. Pre-puberty, they are inhibitory, and post-puberty they are excitatory; it's a fair bit of a change in a very complicated system. Though I can't find that citation right now, there is a good-ish overview of the changes in the pre and post-pubescent neuroanatomy here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5283387/
There is some evidence, in terms of THC, of effects on the growth of mossy climbing fiber neurons and retardation of climbing onset in adolescents. Again, though, I can't find that citation right now. Maybe I need more of the stimulant caffeine? ;)