Hi Sandy
I have been on prednisolone for 24 years, since diagnosis, and yes it can have a variety of side effects. Mood changes, changes in thoughts and behaviour, sleeping difficulties, confusion, blurred vision, anxiety and hyperactivity are a few of the more common effects. We are all different in our responses though and the dosage that affects one person may be insignificant in someone else.
I have been on varying doses but find if I can cope on 7.5mg or less, without excessive joint inflammation, then I am not affected by the unwanted nasties. How long are you expecting to be on 15mg? It may be worth putting up with it until the RA is well controlled, then I imagine your rheumatologist will want to very slowly reduce to a low maintenance dose.
I suspect it really is the steroids! Don't think you're losing your mind just yet
Lyn x