Rising inequality and social isolation have led to an “epidemic of despair” that is driving down fertility rates worldwide, according to a new paper by Penn neuroscientists Michael Platt and Peter Sterling.

This acute sense of loneliness and anxiety is contributing to more physical and mental ailments, particularly in high-income countries, and dampening the most basic of human desires — procreation. The U.S. birth rate has declined by an average 2% a year for the last decade. The global fertility rate has plunged to 2.3 (live births per person) and is expected to continue decreasing below the 2.1 rate needed for population replacement.

“My co-author and I are just kind of gobsmacked by this because this is not what species do. They don’t decline in numbers, because reproduction is the driver of evolution,” Platt said during an interview with Wharton Business Daily on SiriusXM. (Listen to the podcast.)

The paper, “Declining Human Fertility and the Epidemic of Despair,” appears in the journal Nature Mental Health.

“This is not what species do. They don’t decline in numbers, because reproduction is the driver of evolution.”— Michael Platt

Declining Fertility Rates Are Bad for Business

A declining population may be beneficial for a planet already scarred by the effects of climate change and resource scarcity. But it could have profound effects on economies and labor markets, the professors said. Without enough young people, it will be difficult to staff work that requires “young muscle,” such as construction and the military, or find new recruits for fields such as medicine and engineering. There will be fewer consumers overall, and an overall reduction in the wages that generate taxes for programs like Social Security.

“Knowledge work may be a little bit less [affected] because of the rise of AI and tech. But that in and of itself is probably accelerating the conditions that we think are actually driving part of this fertility decline,” Platt said.

The professor pointed to a catastrophic rise in anxiety, depression, and obesity-related diseases such as diabetes that corresponds with the rise of digital culture, where people are interacting with screens more than with each other. The problems are worst among teen girls, who are reporting record high rates of sadness and suicidal thoughts.

“If you’re spending more time on your phone or in front of a screen, you’re not out experiencing real life and making real connections.”— Michael Platt

Government Interventions Have Yet to Slow Fertility Rate Decline

All these factors coalesce to create a “negative momentum,” which the professors explain as a drop in the dopamine-inducing rewards that usually come from material gains and deep social bonds.

“If you’re spending more time on your phone or in front of a screen, you’re not out experiencing real life and making real connections, making real friends,” Platt said. “And you’re potentially limiting your ability to find the person you’re going to fall in love with and start a family.”

The professors argue that government interventions to encourage having babies, like subsidizing child care, have had little effect on the downward fertility trend. More foundational changes are needed, they said. Countries that have banned smartphones at school, for example, have reported improved mental health and less bullying among students.

“I think, unfortunately, what we’re looking at is something more like a restructuring of our economic and social lives,” Platt said. “That’s a big task, but we can start small.”