And even if it was causal, you'd still need to investigate what it is on social media that causes misery, e.g. ideologies/misinformation, social comparison/envy

And even if it was causal, you'd still need to investigate what it is on social media that causes misery, e.g. ideologies/misinformation, social comparison/envy, cyber-bullying, addiction, bad news/sensationalism or echo chambers.