Any parent will tell you kids can be depressing at times. A new study shows that raising them is a lifelong challenge to your mental health. Not only do parents have significantly higher levels of depression than adults who do not have children, the problem gets worse when the kids move out. "Parents have more to worry about than other people do—that's the bottom line," said Florida State University professor Robin Simon. "And that worry does not diminish over time. Parents worry about their kids' emotional, social, physical and economic well-being. We worry about how they're getting along in the...