I have used my Irish Grandmother's cure on 3 children (in my life) all whom were cured immediately ... (she used this on me)
It is a deep set "fear of the dark" she told me when she sat me down , to talk to me ... she said, before you go to sleep , ask St. Brigid to "Please wake me up if I have to go to the bathroom" ... and when you wake up, know that all you have to do is call out to me (that is call out to my grandmother) ... I will hear you and tell you I will let you know I am awake and ... you will be able to get up and go to the bathroom knowing someone else is awake which takes away the fear of the dark ... you also let them know that they should ALWAYS go to the bathroom BEFORE going to be (cuz most kids don't even think about brushing their teeth , let alone going to the bathroom when they don't need to at the moment) ... I was a camp counselor and used it on 3 kids during 5 summers of being a counselor ... all 3 went home cured of bed wetting .... (and in case you aren't a spiritual person, I guess you don't need to use St. Brigid, you can just tell them to tell themselves to WAKE UP... sorry I just thought I'd add a little PC in a PC world .