I don't think it's a good method. You have to cut very deep, and there are a lot of tiny bones, nerves, tendons in the way. If you sever those and fail, you might end up with permanent damage and not be able to use your hands again.
There will be a lot of blood, but clotting is an issue.
It's going to hurt a lot, even with painkillers. You might not be able to actually reach the veins and arteries you need to cut because of that.
You also ideally need to cut both wrists, and I've never figured out how exactly you do that once you've properly injured the first one. I'm sure it's possible, but I can't make sense of it in my head.
Anyway, not a good method. More of a gesture, it seems like.