I was prescribed a very expensive synthetic CB1 agonist for migraine nausea (nabilone) by my primary care MD, and the effect was instantaneous and miraculous. Killed the nausea outright, took a solid 80% off of the pain (it was doing the morphine-type "I can feel it but it doesn't hurt" thing), and there was no euphoria/high or noticeable drug craving or reinforcement that I could detect.
The bad news: it's $50 per milligram (almost $1500 for 10 days worth), Schedule 2 (the same schedule as fentanyl, cocaine, and methamphetamine), and technically approved by the FDA only for nausea caused by chemotherapy. The first FDA approval date for the drug was 1985.
I'd previously tried so many prescribed anti-migraine drugs I couldn't even list them all here in the time I have. The side effects were as debilitating as the migraines themselves in some cases. Some were just wildly inappropriate (e.g. a resident wanted to write opiates). Anyway, I fought with an insurance company for seven days on a $20k/year policy and they still wouldn't cover it.
Given the experience of trying to do this the right way, I'm utterly unsurprised that people in intense pain end up trying to DIY it.