Browsing Facebook could leave you down in the dumps, research has shown.
A new study released on Wednesday found the social network site promotes feelings of envy among users that can lead to depression.
Looking through Facebook has become a daily activity for millions of people, but researchers set out to discover how emotionally involved users are with the social networking site and how regular use can affect their mental health.
Experts at the University of Missouri found Facebook use can lead to symptoms of depression if it triggers feelings of envy among its users.
Professor Margaret Duffy, who co-authored the study, said they way Facebook fans use the site makes a difference in how they respond to it.
She said: "Facebook can be a fun and healthy activity if users take advantage of the site to stay connected with family and old friends and to share interesting and important aspects of their lives.
"However, if Facebook is used to see how well an acquaintance is doing financially or how happy an old friend is in his relationship - things that cause envy among users - use of the site can lead to feelings of depression."
For the study, 700 young Facebook users were questioned. It found that some of those who engage in "surveillance use" of Facebook also experience symptoms of depression, while those who use the site simply to stay connected do not suffer negative effects.
"Surveillance use" of Facebook occurs when users browse the website to see how their friends are doing compared with their own lives.
The researchers found that Facebook postings about things such as expensive holidays, new houses or cars - or even happy relationships - can evoke feelings of envy among "surveillance users".
They say that these feelings of envy can then lead to Facebook users experiencing symptoms of depression.
Professor Duffy said: "We found that if Facebook users experience envy of the activities and lifestyles of their friends on Facebook, they are much more likely to report feelings of depression.
"Facebook can be a very positive resource for many people, but if it is used as a way to size up one's own accomplishments against others, it can have a negative effect. It is important for Facebook users to be aware of these risks so they can avoid this kind of behavior when using Facebook."
The findings are published in the journal Computers in Human Behaviour.