Well actually, there isn't enough evidence to prove or disprove it either way. There's a link of correlation between high end cannbis use and mental health issues, but there isn't evidence to suggest it "causes" mental problems.
http://www.rcpsych.a.../cannabis.aspx?
"Although most people treated for schizophrenia during the follow-up period did not use cannabis during adolescence, those who did use cannabis heavily (i.e. more than 50
times before the age of 18) were six times more likely to be hospitalised for schizophrenia by the age of 33 than those who had not used cannabis. Moreover, those who had used cannabis more than ten times (but less than 50 times) were three times more likely to be hospitalised for schizophrena."
http://www.nationald.../$File/m684.pdf
For anyone who says there isn't a thing such as cannabis induced psychosis, I suggest you work with mental health teams or law enforcement. It's a small number compared to actual amount of users, but it is prevelant and disruptive.
Also you're article about using cannabis as anti-psychotic only focuses on the use high CBD strains (the chemical formula already present in or body), and wouldn't likely have little or no THC make up (the chemical formula that gets you "high"). It doesn't prove that cannabis doesn't cause/aggravate mental health issues at all.
I'm of the opinion that since legal drugs such as alcohol and alcohol induced dementia (
https://www.alzheime...p?documentID=98), sugar and addiction (
https://www.psycholo...r-mental-health), and tobacco and lung cancer. (
http://m.jnci.oxford...1/14/1194.short).
To put it simply, if a consenting adult wishes to partake in consumption of a potentially dangerous substance, then that's their prerogative. With juveniles it's slightly different, and yes you probably shouldn't smoke cannabis until you're 25, but then against you probably shouldn't drink, smoke, have kids, gamble or fight in wars either.
Also you're second study doesn't dismiss the link between schizophrenia and cannbis use, rather just states there isn't a correlation between causing schizophrenia itself. It also fails to hi light the link between cannabis and other mental health problems ( depression, anxiety, dementia, bi-polar, dysmthia, psychosis etc)