Look around you: Imagine modern relationships, interactions, media conversations of today transported back to, say, 1940. Would they seem peculiar or out-of-place? Put aside differences in technology. Focus on the nature of human interaction. Do you sense that self-serving, selfish, exploitative behaviors have worsened among modern people, patterns of behavior that would have been unacceptable in prior times? Self-aggrandizing posts on social media, tattoos advertising some personal agenda, haircuts and hair colors designed to set yourself apart rather than fitting in—was this the norm when your great grandmother was dancing the Charleston or when Americans had to ration gasoline and coffee to support the war effort?

Psychologists have been chronicling the rise of narcissistic behavior over the past 40 or more years. They have developed questionnaires designed to quantify such behaviors, such as the Narcissistic Personality Inventory and the Pathological Narcissism Inventory, both of which suggest a skyrocketing frequency of narcissistic tendencies among modern people. For example, adolescents asked whether they feel that “I am an important person” increased from 12% in 1963 to 77–80% in 1992. Narcissistic phrases such as “I am the greatest” dramatically increased between 1960 and 2008. Witness the explosion of “selfies” on social media. Sociologists have proposed that some of our modern crises stem from narcissism: Wall Street greed, the excessive profit motive in healthcare and pharmaceutical industry, excessive consumption of personal goods financed with debt.

Twenge 2008

If there is one defining characteristic that is lost in narcissists, it is lack of empathy, the lack of understanding of what someone else is experiencing, of not caring for other people’s feelings, not sharing in their joys or pain.

Narcissism needs to be distinguished from self esteem or self confidence. Feeling good about yourself—self esteem—or being confident of your abilities and limitations—self confidence—do not lead to exploitative, self-serving behaviors as narcissism can. In addition to lack of empathy, narcissistic behavior traits include never accepting personal blame and blaming others and a need to control every situation even when you lack ability. And, while it appears that narcissistic behaviors are on the rise, the extreme version, i.e., narcissistic personality disorder, is not increasing.

Curiously, I am witnessing narcissistic behavior unwinding in the people who restore Lactobacillus reuteri to their GI microbiomes, lost due to antibiotics and other factors despite being ubiquitous in hunter-gatherer humans and all other mammals. In other words, people boosting bacterial counts to the hundreds of billions per serving of our L. reuteri yogurt are reporting feeling closer to their partners, to their families, neighbors, and coworkers, feeling a greater sense of generosity, a greater need for the companionship of other people, and acceptance of other people’s opinions—a reversal of narcissistic behavior. Note that this is occurring while the rest of the world is experiencing record social isolation, record suicide, sky-high divorce rates, and, yes, an increase in narcissistic behaviors. There is a lot of agonizing over whether the capitalistic system encourages narcissism, or whether current child-rearing methods are to blame. But what I see happening with restoration of the microbe lost by nearly all modern people, L. reuteri, is a return to what I believe is the way people used to be. Surely, there is more at work in society to account for the rise in narcissism than loss of this microbe. But what other solutions are you aware of that are so direct, so simple?

Could a microbe, so small you can’t even see it with the naked eye, underlie so much about human behavior? I believe it does. And what other aspects of modern human behavior can be backtracked to disruptions of the microbiome—sleep, anxiety, depression, suicide, violence, aggression?