Maybe it's not such a good idea to always know what wonderful things your friends are up to these days. A recent study from Nanyang Technological University, Bradley University and the University of Missouri Columbia revealed that use of Facebook may lead to envy and then sadness. The study of 736 college students showed that users may have symptoms of depression after experiencing envy brought about by reading Facebook updates by friends. Researchers found that Facebook users who reported envy of their Facebook friends were also more likely to report feeling depressed. However, Facebook users who didn't compare their lives to those of their friends didn't experience negative effects. The study was published in Computers in Human Behavior.