While student loans are a painful, long-term expense, they are also an investment in one’s career and earnings prospects. But what does lavish spending on a wedding provide? It can lead to divorce, according to a study by Emory University researchers Andrew Francis and Hugo Mialon. More interesting, they suggest that the stress that comes with wedding debt might be the underlying cause for the unhappy outcomes. Weddings, which peak in early summer and surge again in the fall, have become more elaborate over the years. Engagement rings usually have diamonds – that wasn’t always the case. The average expense for a wedding and reception in this country is now $30,000. But the researchers found that women who spend more than $20,000 on…