"Early experimentation with cannabis which has been shown to lead to problems such as the onset of schizophrenia."

This idea seems to be hanging on even though it has been debunked.  The causality was never shown, but it was speculated upon as people with Schizophrenia have a much higher use of cannabis.  More recent studies have shown that people with mental illness are self-medicating with cannabis, not that cannabis causes mental illness.  In other words, mental illness causes cannabis use, not vice versa.

By no means am I saying that cannabis use is good or healthy, I'm just pointing out that it doesn't cause mental illness.