I've thought about suicide since I was a child. I've taken the thoughts to the literal edge, but I couldn't jump. Which is a good thing, even if sometimes I wish I had. The idea of it being an obsessive thought makes sense. I have other obsessive behaviors as well. It's probably related to serotonin. I think once you've decided that suicide is an option, then your mind always presents it as an option, whether or not it's one you would actually take. I will probably always have it cross my mind and when I am depressed, most likely often. If I start planning, then I'll worry, but my outlook isn't hopeless enough for me to pursue it right now.