Why do you feel lonely? Neuroscience is starting to find answers

With research over the years increasingly pointing to social relationships as a key source of happiness and well-being, Covid driven social isolation has raised concerns about rising mental health issues. Indeed, Ben Carlson wrote about how whilst stock markets are soaring, there is a bear market in happiness. Why, the suicide of a  Bollywood star suffering from mental health issues during the lockdown has been many a living room discussion over the past month (unfortunately, the discourse has moved beyond mental health suppressing an opportunity to create much needed awareness of mental health issues). For many of us, the workplace has been a key source of social interactions which now are hard to come by, exposing us to risks of loneliness. This piece in the MIT Technology Review first shows how there is very little scientific research around the biological reactions to loneliness limiting medical science’s ability to deal with it. The author talks about how that is changing as the pandemic increases the awareness and need to accelerate research in this space. The piece talks about two studies – first in rodents which identified specific type of neurons responsible for cravings for social activity and then among humans which showed that the need for socialising is comparable to that of hunger, both of which trigger increased activity in the mid brain.
“In recent years, a vast scientific literature has emerged linking loneliness to depression, anxiety, alcoholism, and drug abuse. There is even a growing body of epidemiological work showing that loneliness makes you more likely to fall ill: it seems to prompt the chronic release of hormones that suppress healthy immune function. Biochemical changes from loneliness can accelerate the spread of cancer, hasten heart disease and Alzheimer’s, or simply drain the most vital among us of the will to go on. The ability to measure and detect it could help identify those at risk and pave the way for new kinds of interventions.
…quantifying, or even defining, loneliness is a difficult challenge. So difficult, in fact, that neuroscientists have long avoided the topic.
Loneliness.. is inherently subjective. It’s possible to spend the day completely isolated, in quiet contemplation, and feel invigorated. Or to stew in alienated misery surrounded by a crowd, in the heart of a big city, or accompanied by close friends and family. Or, to take a more contemporary example, to participate in a Zoom call with loved ones in another city and feel deeply connected—or even more lonely than when the call began.
This fuzziness might explain the curious results that came back when Tye, before publishing her first scientific paper on the neuroscience of loneliness in 2016, ran a search for other papers on the topic. Though she found studies on loneliness in the psychological literature, the number of papers that also contained the words “cells,” “neurons,” or “brain” was precisely zero.”
Tye came across the work of Gillian Matthews. As a graduate student at Imperial College London, Matthews had made an unexpected discovery when she separated the mice in her experiments from one another. Social isolation—the very fact of being alone—seemed to have changed brain cells called DRN neurons in ways that implied they might play a role in loneliness.
…One of the first things Tye and Matthews noticed was that when they stimulated these neurons, the animals were more likely to seek social interaction with other mice. In a later experiment, they showed that animals, when given the choice, actively avoided areas of their cages that, when entered, triggered the activation of the neurons. This suggested that their quest for social interaction was driven more by a desire to avoid pain than to generate pleasure—an experience that mimicked the “aversive” experience of loneliness.
Scientists have long known that the brain harbors the biological equivalent of a car’s fuel gauge—a complex homeostatic system that allows our gray matter to track the state of our basic biological needs, like those for food, water, and sleep. The purpose of the system is to drive us toward behaviors aimed at maintaining or restoring our natural state of balance.
Tye and Matthews seemed to have found the equivalent of a homeostatic regulator for the basic social-contact needs of rodents.”
A similar study involving humans showed activity in the brain linked to social isolation:
“Last year, Livia Tomova, a postdoc who has been overseeing the research in Saxe’s lab, recruited 40 volunteers who self-identified as having large social networks and very low levels of loneliness. Tomova exiled her subjects to a room in the lab and forbade any human contact for 10 hours. For comparison, Tomova asked the same participants to come back for a second 10-hour session that contained plenty of social interaction, but no food.
At the end of each session, the subjects were asked to climb into the fMRI scanner and were exposed to different images: some showed people offering nonverbal social cues, and others contained pictures of food.
Unlike Tye and Matthews, Tomova was unable to home in on individual neurons. But she was able to track changes in blood flow within larger areas of the scan, known as voxels; each voxel displayed the changing activity of discrete populations of several thousand neurons. Tomova focused in on areas of the midbrain known to be rich in the neurons associated with producing and processing the neurotransmitter dopamine.
…Insights into the circuitry of loneliness in the brain might also shed some light on addiction, which isolated animals are more prone to, according to some research. The evidence appears particularly strong in adolescent animals, which seem to be even more sensitive to the effects of social isolation than older or younger ones. Humans between the ages of 16 and 24 are the most likely to report feeling lonely, and this is also the age when many mental-health disorders first begin to manifest. Is there a connection?”
Tye’s research will likely trigger a whole new body of work that can be crucial in future as technology minimises the need for social interaction among humans.