Thirst is an aversive signal, that motivates us to search for drinkable water prior to falling victim to dehydration. And pain is an aversive system that notifies us of potential tissue damage and motivates us to take care of our physical body.
You might think that the biological warning machinery stops there but there’s more. Although not common sense, although not intuitive, the pain and aversiveness of loneliness, of feeling isolated from those around you, is also a part of biological early warning machinery to alert you to threats and damage to your social body, which you also need to survive and prosper.
Just about all of us have felt physical pain and nearly all of us have felt the heartbreak of home sickness, the agony of bereavement, the torment of unrequited love and the pain of being shunt. All of these are variations on the experience of loneliness.
When I started to study the effects of loneliness and brain and biology a couple of decades ago, loneliness had been characterized as a non-chronic disease without redeeming features. It was even equated with shyness and depression with being a loner, a person with marginal social skills. Scientific measurements and sophisticated calculations, to our surprise, revealed that these were myths.
Science and common sense had again produced two very different depictions of a phenomenon. And yet if you look at the way we are increasingly living our lives, it shows the extent to which we still buy in to those myths of loneliness and values of autonomy and independence. For instance, if you look at the percentage of one-person households in 1940 across the US it was largely less than 15% of the households by state.
Fast-forward to 1970, and it’s grown to be between 15% and 20%.
Fast forward to 2000 and it now exceeds 25% in most states in America. And that light blue state, Utah in the 2010 census has gone darker blue.
The prevalence of loneliness is also on the rise. In the 1980s, scholars estimated that about 20% of Americans felt lonelier than at any given point in time. Two recent nationally representative surveys indicate that this number has doubled, but you don’t hear people talking about feeling lonely, and that’s because loneliness is stigmatized. The psychological equivalent to being a loser in life or a weak person. And this is truly unfortunate because it means we are more likely to deny feeling lonely, which makes no more sense than denying we feel hunger, thirst or pain.
For living with loneliness we now know is the major risk factor for broad-based morbidity and mortality. Consider a couple of the conditions we know about — premature death. Living with air pollution increases your odds of an early death by 5%. Living with obesity, we know, a national health problem, increases your odds of an early death by 20%. Excessive alcohol consumption: 30%. A recent med analysis of around a hundred thousand participants shows that living with loneliness increases your odds of an early death by 45%. We’re not the only social species and the experimental investigation of non-human social animals who were isolated shows they too suffer deleterious physiological consequences and an abbreviated lifespan.
Across our history, as a species, we have survived and prospered by banding together, couples, families and tribes, for mutual protection and assistance. We think of loneliness as a sad condition, but for social species, being on the social perimeters, not only sad, it is dangerous.
The brains of social species, including our own, have evolved to respond to being on the social perimeter by going into a self-preservation mode. If you isolate a rodent and then put it in an open field such as these dots at the bottom of the image, it engages into what’s called predator evasion, it walks around the outside and doesn’t venture into the middle where escape from a flying predator would be more difficult.
When humans feel isolated, they’re too, not only in an unhappy circumstance, but in a dangerous circumstance. And their brains too snap into a self-preservation mode.
In a brain-imaging study that we conducted, we showed people negative images that had nothing to do with other people or negative social images, while they were sitting in a scanner and we were scanning. What we found was the lonelier the brain, when a negative social image was presented, that is in a person’s environment, when something negative socially happened, the brain allocated more attention, greater visual cortical activity depicted in yellow here, to that image.
Now, as you follow that image forward, you come to those two blue areas: that’s a temporal parietal junction. This is a piece of brain tissue that’s involved in theory of mind, in mind reading and mentalizing, in taking another person’s perspective and empathy. It’s responsible for the attentional control required to step out of your head and put yourself, at least figuratively, inside the head of someone else so you can take their point of view.
The lonelier the brain, when something negative in the social context was depicted, the less the activation in this region. It’s dangerous on the social perimeter. When something happens negative in the social environment, that brain is focused on self-preservation, not a concern of the other person.
The similarity in neural and behavioral effects across phylogeny is a testament to the importance of the social environment for social species. And these deep evolutionary roots tilting our brain and biology towards our self-preservation also suggest that much of what’s triggered by social isolation is non-conscious.
For instance, when you feel isolated you feel this motive, this desire, this intention to connect with other people again. What you don’t feel, is that your brain has gone into a hypervigilance for social threats and this hypervigilance means you introduce intentional, confirmatory and even memory biases in terms of those social interactions. And if you’re looking for dangers, you’re more likely to see dangers whether they exist or not, meaning that you’re more likely to have negative interactions. And that threat surveillance of always looking for the next foe activates neuro-biological mechanisms that can degrade your health and lead to early mortality.