Most phobias have their roots somewhere in your past I think. I am phobic of stairs also. I fell down ours with the baby. No one was really hurt but the possibility was so strong that it could have been worse I have developed a terror of them. I watched a movie about fire ants when I was little. More like I was forced to watched by my adult brother. The people were covered by them and one person ran of screaming and was eaten. i was like 6. To this day I have issues with ants. If one is one me it freaks me out so badly. I will wake up at night thinking another got on me. Its irrational and I can tell myself that all day long. Its no help. I don't think having a phobia means you are unstable or ill. If it becomes debilitating then you might need help with it but many many people have them. Many just don't admit it or label them as a phobia. Instead of a phobia I just say I have a thing about ants and stairs. You add a little shudder and people laugh and will admit to their own "things".