Decadron is a strong cortico steroid...it can have temporary effects on the elderly in terms of psychosis, insomnia, agitation...increases in glucose in diabetics and prediabetics. I deal with wacky granny situation a lot with elderly folks on decadron.
It can happen but 6 a day for short term is generally not a high enough dose to do that. In addition Trump has. it show. any evidence of being wacky.....