If you really dig into the study and results you will see at the end, there are very few people in the highest income category, only 1.2%. So, you could have a problem with results if you happened to have an abnormal amount of 'unhappy' in the highest income (as defined by the study's questions) people respond to the study because of the small size at this income level (it is only about 340 people at this income level so just a few people could skew results for this category). Also, they are going off of income, not assets/net worth. I could have $30 million of Muni bonds, what is my income, $0. Finally, on income, it implies that they are focusing on working people, in fact the average age is in the 30s.
The other big issue is their binary questioning. Meaning, if a higher income person is really, really, really happy their response for analysis in the study would be the same as a person who is 'just' happy and that 'just' happy person makes half of what the high income really, really, really happy person makes.
As you can tell, I think these types of studies are silly. What are they trying to accomplish? A way to make someone struggling to get by because they live in a HCOL area making $80,000 a year that they should feel happy because others in their same income category are? They do not even take geography into consideration.
I remember when I was building my business and struggling, I was happy (working hard, using my brain, building something, etc.). I am blessed to be sitting on some money and I am happy now for other reasons (spending time with wife and kids, travel anywhere on a moment's notice, etc.).
Finally, anyone who says money does not help is, I do not believe, being honest. It takes a major stressor off the table and more importantly, it buys time, and time is one of the few limitations in life.