From what I can find, the correlation between social media use and mental health problems is small [1] or nonexistent [2]. There are few causal studies, and their results are even smaller, eg: halting Facebook usage for a month decreased depression by 0.09 stdev [3].
[1] "We found a small but significant positive correlation (k=12 studies, r=.11, p<.01) between adolescent social media use and depressive symptoms."
https://www.sciencedirect.com/science/article/abs/pii/S01650...
[2] "There was no association between frequency of social media use and SITBs [self-injurious thoughts and behaviors] however, studies on this topic were limited."
https://www.sciencedirect.com/science/article/abs/pii/S02727...
[3] "A study using an experimental design measured the effects of abstaining from Facebook for four weeks in an adult population and found that there was a slight decrease (SD=0.09) in depression."
https://www.sciencedirect.com/science/article/abs/pii/S01650...