People who use social media most often tend to have higher rates of depression, according to new research .
The study looked at over 1,700 adults in the US. The group was evenly split on gender and were fairly racially representative. Researchers asked subjects to report how often they use social media each day and subjects filled out standard questionnaires about their depression.
The subjects were divided into four groups based on how much they used social media. The group with the highest rate of social media use had "significantly increased odds of depression," even when all other factors were controlled for, when compared with those with the lowest rate of social media use.
Is this because social media tends to make people depressed or because depressed people turn to social media for social support (or is it something else entirely)? We don't know. This study only looked at the correlation between social media and depression.
Some previous work  has offered evidence of a causal link between Facebook use and unhappiness in younger people. They found that using Facebook made people less happy. The researchers explicitly ruled out the explanation that people turn to Facebook when they are feeling bad by testing people's well-being before and after using the site. Of course, feeling a bit sadder is not the same thing as depression, and thus this previous work does not wholly explain what was found in the new study.
On the other side, there is also research that shows social interaction online can increase feelings of self-esteem and social support and decrease loneliness and depression . So we know that there are also emotional benefits that come from using social media.
Understanding the direction of this link will be important going forward. If social media use can cause or exacerbate depression, there is work to be done on identifying why and potentially guiding at-risk users away from these sites. On the other hand, if depressed people turn to social media for emotional support - and if there is evidence that it can help - then we may actually want to encourage social media use among depressed patients.
The likely answer (as with most things) is "it's complicated." Just as is true of offline socializing, depending on how people interact on social media and with whom, the effect may vary. Much more research is necessary to understand these nuances, and there is a wealth of insight to be found in exploring these links.
 Sidani, Jaime E., et al. "Association between social media use and depression among US young adults." Depression and anxiety 33.4 (2016): 323-331.
 Kross, Ethan, et al. "Facebook use predicts declines in subjective well-being in young adults." PloS one 8.8 (2013): e69841.
 Shaw, Lindsay H., and Larry M. Gant. "In defense of the Internet: The relationship between Internet communication and depression, loneliness, self-esteem, and perceived social support." Cyberpsychology & behavior 5.2 (2002): 157-171.