I notice in our house (husband and son are BiPolar (BP)) that they are not in synch, they do not cycle at the same time but that one will start, then get settled then the other ones does the same. I wonder if having one cycling triggers the other one? Right now difficult child is good, husband is a PITA! and yes, he gets caps for that.
I am not sure if there is any research that validates any of this, I will look and see what I can find.