Suffered from this at 19 because I was trying to self-medicate my undeveloped brain. It can manifest itself in many different ways, either as entirely new disorders, exasperating pre-existing conditions, or being enough to ignite dormant conditions and turning an otherwise "healthy" kid into a full blown schizophrenic.

Adults can suffer from this but it is far more prevalent in youth. In my case I went manic and literally thought I was going to die. I was thoroughly convinced that my life was effectively over and that a clot or something would strike me dead at any second. Took many months of in-stay therapy to stabilize myself.

Whats crazy is that I started smoking again a couple of years ago as a much older man and I've had a wonderful experience. I think it has its benefits but is incredibly dangerous for youth. Like, teens smoking pot turn into dangerous and violent offenders. Im scared of teenage potheads.