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Loneliness alters your brain's social network: Feeling disconnected from others is reflected by how the brain represents relationships -- ScienceDaily

Thinking about someone from each category corresponded to a different activity pattern in the mPFC: one for the self, one for the social network (both friends and acquaintances), and one for celebrities. The closer the relationship, the more the pattern resembled the pattern seen when thinking about the self. These brain patterns differed for lonelier individuals. Activity related to thinking about the self was more different from activity related to thinking about others, while the activity from thinking about others was more similar across social categories. In other words, lonelier people have a "lonelier" neural representation of their relationships.

Loneliness in young adults linked to poor sleep quality -- ScienceDaily

Loneliness is defined by researchers as a distressing feeling that people experience when they perceive their social relationships to be inadequate. This is distinct from the concept of social isolation, as people can be socially isolated without feeling lonely, or feel lonely despite being surrounded by many people. While the effect of being lonely is well documented among the elderly, it is a common problem for young people too -- the Mental Health Foundation reports that loneliness is most frequent between the ages of 18-34. Despite this, little is known about health problems that are associated with loneliness among young adults, or the impact on sleep.
Even when you’re careful about picking a spot—protected forest, wild coastline, lonesome desert alongside a national park—you need a form of income and you need interludes of friendship and love and other problems. It doesn’t matter if you’ve got a whole crowd in the nearest city, because they will rarely if ever visit. People are lazy. Even the smart ones toss away most of their “free time” watching television. You’re on your own out there, and even Henry David Thoreau got lonesome and went back to town. Your rural neighbors might be fellow conservationists and tree huggers, but they’re more likely gun nuts with a sheet-metal garage crowded with dirt bikes and off-road buggies.