A study co-authored by a University of Maryland researcher says unhappy people watch more television.

Sociologist John P. Robinson, the study's lead author, found that people who described themselves as "not too happy" watched 5.6 hours more of TV a week, compared to their jolliest counterparts.

Published in the December issue of the journal Social Indicators Research, the study finds that happy people spend more free time participating in religious services, socializing with friends and having sex.

Researchers say the findings don't mean watching TV makes people unhappy, but indicates that there is a link that's yet to be understood.

The findings are based on a survey of nearly 40,000 people ages of 18 and 64. Overall, most respondents were happy; the "not too happy" folks accounted for 11 percent of the total.