A small study suggests that for adolescents, their number of Facebook friends may be related to their stress levels, with more than 300 friends associated with higher levels of the stress hormone cortisol.
The study only included 88 participants at one point in time, so it can't indicate whether changes in Facebook metrics cause an increase in stress, or vice versa.
Other important external factors are also responsible for cortisol levels, but Facebook involvement may have its own effect, senior author Sonia Lupien of Montreal Mental Health University Institute said in a statement.
"We were able to show that beyond 300 Facebook friends, adolescents showed higher cortisol levels; we can therefore imagine that those who have 1,000 or 2,000 friends on Facebook may be subjected to even greater stress," she said.
The 88 teens in the study, age 12 to 17, answered questions about their Facebook use frequency, number of friends, self-promoting behavior and supporting behavior of friends. The researchers measured the teens' cortisol levels four times a day for three days.
Kids who had more than 300 Facebook friends tended to have higher cortisol levels than those with fewer friends, the researchers reported in Psychoneuroendocrinology.
With more peer interaction on Facebook, however, cortisol levels tended to be lower. Neither depression nor self-esteem were related to cortisol levels.
Cortisol levels in early adolescence may influence risk of depression years later, the authors wrote.
Wenhong Chen of the department of Radio-TV-Film and the department of Sociology at the University of Texas at Austin, who was not part of the new study, points out that the research is about Facebook, and so the findings can't necessarily be generalized to other forms of social media use.
It may also not be generalizable to other age groups, Chen said.
"The preliminary nature of our findings will require refined measurement of Facebook behaviors in relation to physiological functioning and we will need to undertake future studies to determine whether these effects exist in younger children and adults," Lupien said. "Developmental analysis could also reveal whether virtual stress is indeed 'getting over the screen and under the skin' to modulate neurobiological processes related to adaptation."
Offline friend network size was also related to cortisol levels.
"It may not be about the number of friends either online or offline, it may be more about potential communication overload," Chen told Reuters Health by email.
Larger networks may mean more peers and more drama, she said.
Rather than using the overall number of friends online or offline it may be more revealing to examine network composition, strong ties and weak ties, as well as individuals' position in their networks, she said.