Anxiety and FOMO are directly related to social vulnerability about current and future social settings in which we do crave to be included and accepted. Social anxiety is more commonly involves an avoidance of social situations or a fear of being in a social situation that you can't get out of. In contrast FOMO is not diagnosable in a professional sense, it also concerns a fear of not being present in social situations whereas social anxiety involves that fear that kicks in once we're in them. So there are some tenuous links between social anxiety and this fear of missing out. They're both directly related to relationships and the social element of our psychology but FOMO seems to be its own