Ahhh--- NO.
Cannabis can intensify or trigger mental illness in people who already suffer from some mental infirmity or propensity towards mental illness. It can also do many positive things like calm nerves, dull pain, help people sleep, aid in religious ceremonies. But it doesn't necessarily /cause/ anything.
Some of the smartest, sanest men in history were pot smokers.
Nor does psychoses lead to violence. Many psychotics are violent, many are not. It depends on the condition and circumstances.