There’s huge volumes of studies that show that pot causes psychosis, schizophrenia and brain damage.
While there’s huge association with Schizophrenia and Psychosis, nobody can answer: Which came first, the chicken or the egg? There are people alive today who have been smoking pot for 50+ years without either condition.
And, brain damage/change is a given and undisputed effect. But it pales in comparison to the organic brain damage/change effected by alcohol.
Alcohol is legal in all 57 states. Each of them chose to allow people to succeed or fail in these matters.
Would you presume to dictate a course and outcome for everyone...in all 57 states? Or are you just observing the FACT that pot is not harmless?
It is estimated that 40 to 45 percent of people will end up on a psych ward for a short stay with temporary symptoms of psychosis, schizophrenia etc just from simple life stresses.
The question for me is one of severity and length of treatment and speed of recovery. For some the stay is short; for others the condition lasts a lifetime.
The role mind altering substances play is not fully understood. No matter how much you caution/educate people there will always be people who ignore sound advice.
My advice is to err on the side of caution and avoid all of it.