Interesting point -- that happy people watch less TV than unhappy people -- but it really doesn't deal with causality. Are people watching TV more because they're unhappy? Or are they unhappy because they're watching more TV?
One point the study apparently makes is that they biggest predictor of how much TV people watch is unemployment. If you don't have a job, you have more time to watch TV, but you're unhappy because you're out of work and have less money and less status.
What Happy People Don’t Do - NYTimes.com