Can the usage of social media contribute to mental disorders or are these mental disorders already present before usage of social media?

Not either/or: It's probably the case that fits the old saying. "it's neither 'either' 'or' - it's both - and more!" people with a fragile adjustment can falter or be shaken by many common activities and some of them are riskier than others for individual reasons. If one has fairly good judgement, it helps to stay safe - if not, taking advise from folk who care about you may be a good idea.

We are living in a: "Brave New World" with both amazing opportunities and dangers. Social media, like social interactions can be assets enhancing lives and improving mental health or deficits contributing to and increasing mental disorders. On one hand anonymousness and lack of oversight of social media can lead to bullying and abuse. When used for social good, it can lead to wonderful encounters and accomplishments.