This is the response I received via email from an Israeli scientist that has been studying cannabis for 50 years...
"I believe that you need high CBD - as high as you can obtain. In schizophrenia doses of 800 mg/day were administered. THC levels are limited by the side effects - but it seems be valuable as individual patients claim that cannabis (which in most cases means high THC) helps them."
High CBD, especially very high CBD (like Charlottes Web or AC/DC) is MUCH harder to find than regular high THC. As Greg said, smoking/vaporizing is probably not the best idea and won't give you high concentrations of cannabinoids. I am C9orf72 positive, currently undiagnosed with probable early symptoms. I am hoping cannabis will help me delay onset and ultimately slow progression once I am diagnosed. With so little information or anecdotal reports, dosing is unknown, so it is a guessing game. I am currently using a high CBD oil during the day, and regular at night.