OP: What are the things that cause loneliness and exacerbate it?
I see the desire for companionship as a type of sensual craving (kama tanha). When you engage in social media and obtain the pleasure of companionship and entertainment by chatting with others, you could increase this craving. When you imagine pleasures you could enjoy, by watching the lives of other people, who delight themselves in things that you have not, again, you could increase this craving. When you watch others, you could also experience the craving to become like them (bhava tanha).
When craving is not met, it leads to negative feelings. In this case, when the craving for companionship is not satisfied, it leads to loneliness.
OP: What are the non-social antidotes to loneliness?
As stated by other answers, you can redirect your mind to other pursuits, for e.g. reading a book. I suggest the book "In the Buddha's Words" by Bhikkhu Bodhi. Please also see this answer.
OP: Does active and directed attention, whether in meditation or
attending to tasks, alleviate feelings of loneliness in the long term?
OP: what is the Buddhist view on social media use?
Is it inherently fragmenting awareness as I suspect?
Does it have no benefits?
Over-excessive indulgence in social media could be akin to habitual partying, with potential exposure to bad companionship and potentially increasing laziness.
According to the Sigalovada Sutta:
"These are the six dangers inherent in habitual partying: You
constantly seek, 'Where's the dancing? Where's the singing? Where's
the music? Where are the stories? Where's the applause? Where's the
"These are the six dangers inherent in bad companionship: any rogue,
drunkard, addict, cheat, swindler, or thug becomes a friend and
"These are the six dangers inherent in laziness: saying, 'It's too
cold,' one does not work; saying, 'It's too hot,' one does not work;
saying, 'It's too late,' one does not work; saying, 'It's too early,'
one does not work; saying, 'I'm too hungry,' one does not work;
saying, 'I'm too full,' one does not work. With an abundance of
excuses for not working, new wealth does not accrue and existing
wealth goes to waste."
Of course, it is also possible to find good friends and be a good friend to others through social media. From the same sutta above:
"Young man, be aware of these four good-hearted friends: the helper,
the friend who endures in good times and bad, the mentor, and the
"The helper can be identified by four things: by protecting you when
you are vulnerable, and likewise your wealth, being a refuge when you
are afraid, and in various tasks providing double what is requested.
"The enduring friend can be identified by four things: by telling you
secrets, guarding your own secrets closely, not abandoning you in
misfortune, and even dying for you.
"The mentor can be identified by four things: by restraining you from
wrongdoing, guiding you towards good actions, telling you what you
ought to know, and showing you the path to heaven.
"The compassionate friend can be identified by four things: by not
rejoicing in your misfortune, delighting in your good fortune,
preventing others from speaking ill of you, and encouraging others who
praise your good qualities."
Social media is like a knife that both the surgeon and the murderer could use, in my opinion.