Radtke muses on the topic of loneliness from many angles. One is the toll it takes on a person's health:
In 2017, a research team aggregated seventy studies, totaling over three million subjects, and found that those who reported feelings of loneliness were more likely to be dead by the time the studies were over than those who identified as socially fulfilled.
Those who lived independently were thirty-two percent more likely to have died within a seven-year period than those who shared their homes with others.
...the difference in life expectancy between those who are socially isolated and those who are not is too great to attribute its cause only to individual behaviors, like smoking or drinking or sitting still.
The problem isn't so much in the time one spends alone, but in how one feels about that loneliness.
...in those who are chronically lonely, Dr. Cole told me, "just about every high-prevalence killer in contemporary epidemiology gets you faster."
I have, in the past, gone through long periods of feeling extremely isolated. To me, saying that loneliness will make you ill feels a bit like saying that being lit on fire will damage your clothes: it's true, but it's a rather secondary concern. The worst part of loneliness is the misery that comes with it. (I can at least attest that it's a solvable problem—given patience, effort, and luck.)
Loneliness also has negative effects on our behavior:
Participants in [Baumeister and Twenge's] studies who'd been made to feel left out showed less brain activity in the areas responsible for executive control than those who were not excluded.
In a companion study, those who felt isolated were more willing to inflict pain on strangers—even those they knew hadn't personally wronged them.
I might suggest that this is a practical reason to be very cautious about using ostracism to try to change (or punish) people's beliefs and behaviors.
Radtke notes that our media sometimes glorifies the very traits that can condemn us to loneliness:
Contemporary male TV protagonists ... drink hard alone in bars, eyes focused on middle distance, placating the unbreaking stream of attractive women who perch down next to them, unfulfilled and underwhelmed by what those around them can provide. ... They are too brilliant to bother with the banalities of the everyday, too haunted by their troubled childhoods to let anyone get close.
She uses Don Draper as an example:
Almost all of his actions are laced with a disinterest in others, but this is the important part: it implies superiority, and only when a man is superior to others is his loneliness meaningful instead of pathetic.
A woman's loneliness, meanwhile, may be treated as something convenient for men:
Pop songs are still sung to women who are beautiful but don't know it. Their beauty is for others, and for the man singing his song, who seems to know he is getting something for free. He benefits from her beauty without its threat—she won't leave, she won't ask for too much, because she hasn't learned the value of what she has.
One of the most fascinating sections in the book is a biographical sketch of Harry Harlow, an unpleasant-sounding man who ran horrifying experiments on monkeys, but whose work helped discredit very harmful theories about child-rearing.