I ask because I've done colonoscopy a few times (I have IBS plus family history of colon cancer) and not once did I get general anesthesia or anything that impacts my brain. It hurts a bit (mostly from the gaz they use to inflate the colon) and yes taking biopsy is a quick sharp pain but it's really not that bad.

Likewise for endoscopy (that's significantly more uncomfortable than colonoscopy though). At least in Europe and in Japan, general anesthesia is not part of the sop.