C.O.
My son had one when he was around 3 and named him Anni (like as Anakin Skywalker). I think he was around 5 when I stopped hearing him talk to or talk about Anni. I think it's just something he outgrew. Sometimes I'll ask him about Anni and he goes "Oh yeah, my imaginary friend!" My son is now 8 and has no effects from it if that's what you're worried about.