YMMV but my prescribed cannabis usage did not impact my life insurance premium. I was worried it would, but knew that the blood + urine tests would show usage anyway. It worked out for me.
There was a whole section of my application regarding cannabis usage. I provided my medical rec. There was a question about seeing a psychiatrist regarding cannabis usage (no). No questions about consumption method. My premium was that of the quoted non-tobacco premium, so I don't think it was affected at all.