it's not generally suicidal ideation, i'd say that is a malfunction of the intrusive thought mechanism.

far as i can tell it exists as our brain simulating what could happen, we see a cliff and go "i could throw this baby off the cliff", and we're supposed to immediately go "jesus fuck that would be horrible, i should hold onto the baby tighter and keep an eye out for anyone else who looks like they might throw a baby off the cliff, also maybe we should do something to prevent people from being able to throw babies off the cliff".