Why are Southern Middle-Aged People So Sad?

Via Economix, I see this Gallup report on Americans' well-being (their emotional, physical and fiscal health). In broad strokes, the happiest Americans are older, richer and living out in California. The least healthy are middle-aged, lower-middle-class, and southern. Why?

Dig into the numbers and you begin to see some interesting gaps in well-being. The healthy behavior index is almost 10 percent higher in the West compared with the Midwest and South (68 vs. 63.3, 63.1, respectively.) Separated couples have a low 56.2 overall well-being rating, compared with married couples' 69.4. Asians lead all ethnicities. Well-being goes up with every income level, and work environment is rated best in the West and worst in the Northeast.

Here are the overall numbers, graphed over the last eight months, by age and region.

Given that Gallup's well-being index correlates so highly with income, the regional breakdown doesn't surprise me. But why should middle-aged Americans rank so low? I'm thinking lingering investment, home equity and retirement anxieties. Other thoughts on the poll?