The vulnerable will deal less well with severe emotional distress than others. Other than that I don't agree that most normal people suffer some of the symtoms listed but the obsessional phase of love is very similar to other forms of obsession.
In essence you are in a state of anxiety until you are with your lover. Not pleasant but then the reason why people like falling in love (vs being mentally ill) is that it's fantastic when you are with them. The rollercoaster of extreme highs and lows is mediated by brain chemicals as are all emotional reactions.
I think it's playing with semanitics to sell a book. If you are ill then you have some form of abnormal functioning. Love is part of the human condition, it's not an illness. You could say any major emotional experience looks like illness: childbirth, divorce.
What do I know? I'm as crazy as the rest of you loons
