My suggestion is that he or you(or perhaps both) maintain a daily
journal detailing mood swings, appetite, whether medications are being taken as prescribed, any memory losses or lack of concentration, his daily diet and whether or not he exercises and if so, how much and what kind..
Although, this might seem like a lot, it'll prove to be most useful for his psychiatrist in making an accurate diagnois and prescribing the proper medication(s) and/or adjunct therapy, if appropriate.