Call it the revenge of Quinn Morgendorffer: no matter what you end up buying the angsty malcontent in your life for the holidays, a new study has proven that their bad attitude is bound to continue in a vicious cycle.  Data collected from 10,000 American teenagers by University College London and the University of Warwick appeared in the journal Proceedings of the National Association of Sciences, which judged the kids' happiness on a scale of one to five, found that those who were happiest as young adults grew up to make about $8,000 more than those who ranked the lowest on the teen happiness scale.  Meanwhile, the saddest of the adolescent bunch earned about 10% less than the others.  This held true despite all of the other factors researchers took into consideration: IQ, education level, self esteem and height. 

Accordingly, when it came to siblings—a good test model due to their identical backgrounds and socioeconomic starting points—the happier brother or sister studied grew up to earn a larger paycheck than their depressed counterparts.  Of course, there are more than a few contextual situations that aren't accounted for in the study, e.g. undiagnosed clinical depression (which, given some psychiatrists' hesitation to medicate adolescents, is often held for treatment until the kid's early 20s).  Nevertheless, it's an interesting concept, as the question of money and happiness have been tumbling in a timeless "chicken vs. egg" theoretical washer/drier for ages.