The other night I wandered back up to my old uni (they were having an open day thing) and I sat in on a psychology lecture. They were debating about what an emotion is and how easy/viable it is to try to change other people’s emotions i.e. if you see a friend looking upset, is it better to help them or should you leave them to it?
Near the end a member of the audience asked one of the speakers if it is scientifically proven that money makes people happier, and the scientist person said that it was, but only to a point. Obviously everyone needs enough money to be happy, but by doing a cross-section of all the households in an area they discovered that after a certain point it levels off and that having huge amounts of extra cash makes no difference. She also said that wealth-related unhappiness came not from how much stuff you had as such, but from comparing how much stuff you had to your peers, meaning that even millionaires become unhappy when they compare themselves to billionaires.