For teenage girls, controlling for smartphone use, what is the relationship between social media and eating disorders?

The sample is teenage girls, as they tend to be the most affected by eating disorders.

The control variable is how often they have access to a smartphone. Social media is typically used on smartphones, but can also be used on computers.  By controlling how much these girls have access to social media, we can see how it affects their likelihood for developing an eating disorder.

The independent variable is how much access and how often these girls use social media. We could either put together a focus group of teenage girls or send out a survey asking about their social media use, like how often they use it and what apps they have,

The dependent variable is the likelihood that these girls will have or develop an eating disorder. This, again, could be done through a focus group or a survey by asking, if they have ever thought of restricting their diet to look a certain way, if they have done so before, or if they are doing so now.