It's called "social comparison theory," which says that people can't help comparing their lives to the lives of others.

And when you watch something like the Academy Awards…where beautiful, rich people get awarded for being so great…it affects your self-esteem, whether you realize it or not.

Social comparison theory also explains why so many people get addicted to BAD celebrity news…like everything Lindsay Lohan does…because it's the easiest way to feel BETTER than celebrities.

And it makes us feel okay about not getting to wear designer clothes and go to all the great after-parties.

So, if you're feeling more depressed than you usually do on Mondays, pick up an issue of "Us Weekly" and start reading.  Or better yet, listen to anything Charlie Sheen has said in the past week.