What is the best predictor of happiness among lawyers?

The Smithsonian Magazine has a review of an article that attempts to determine the factors that go into making a lawyer happy.  According to the article it was not the prestigious lawyers, or those who did the best, or even those who made the most money who were the happiest. It was actually those who had the lowest incomes and the lowest grades in law school—most of whom were public service lawyers.  The abstract of the study reads as follows:

Attorney well-being and depression are topics of great concern, but there has been no theory-driven empirical research to guide lawyers and law students seeking well-being. This article reports a unique study establishing a hierarchy of five tiers of factors for lawyer well-being, including choices in law school, legal career, and personal life, and psychological needs and motivations established by Self-Determination Theory. Data from several thousand lawyers in four states show striking patterns, repeatedly indicating that common priorities on law school campuses and among lawyers are confused or misplaced. Factors typically afforded most attention and concern, those relating to prestige and money (income, law school debt, class rank, law review, and USNWR law school ranking) showed zero to small correlations with lawyer well-being. Conversely, factors marginalized in law school and seen in previous research to erode in law students (psychological needs and motivation) were the very strongest predictors of lawyer happiness and satisfaction. Lawyers were grouped by practice type and setting to further test these findings. The group with the lowest incomes and grades in law school, public service lawyers, had stronger autonomy and purpose and were happier than those in the most prestigious positions and with the highest grades and incomes. Additional measures raised concerns: subjects did not broadly agree that judge and lawyer behavior is professional, nor that the legal process reaches fair outcomes. Specific explanations and recommendations for lawyers, law teachers, and legal employers are drawn from the data, and direct implications for attorney productivity and professionalism are explained.