I've been around cannabis for about 5 decades so I wonder where about your fact statement "that it can cause mental illness in a significant proportion of people" is based on.
Do you have any reference that you can share with us ?
The only people I've seen getting some kind of reinforced mental illness after getting high are those people that already were mentally unstable before.
It's like with booze, some people can handle it others go nuts
But the real drug problem in Thailand & South East Asia is meth.
Compared to ganja there you have a drug that breaks you down, mentally and physically.
Since Prayth and his goons took over, the meth tsunami has quadrupled.
60% of the prisoners has mental problems caused by years of smoking jaba.
Like I've said before; nobody is interested smoking hemp with 0.2% THC. In my country that has one of the strongest drug laws in Europe, hemp has always been legal because people understand how ridiculous it would be smoking it. Leave it to the rope and clothes industry.