I feel that this is relevant to the discussion:

https://en.wikipedia.org/wiki/Behavioral_sink

Behavioral sink is a term invented by ethologist John B. Calhoun to describe a collapse in behavior that can result from overpopulation.

Many [female rats] were unable to carry the pregnancy to full term or to survive delivery of their litters if they did. An even greater number, after successfully giving birth, fell short in their maternal functions. Among the males the behavior disturbances ranged from sexual deviation to cannibalism and from frenetic overactivity to a pathological withdrawal from which individuals would emerge to eat, drink and move about only when other members of the community were asleep.

Having reached a level of high population density, the mice began exhibiting a variety of abnormal, often destructive, behaviors including refusal to engage in courtship, and females abandoning their young. By the 600th day, the population was on its way to extinction. Though physically able to reproduce, the mice had lost the social skills required to mate.

"Calhoun's work was not simply about density in a physical sense, as number of individuals-per-square-unit-area, but was about degrees of social interaction."

Obviously rodent studies are only so applicable to humans, but I see myself and worrying modern societal tends in some of their behavior and the ways they suffer.

I think that when we interact with too many strangers every day that we're unable to make meaningful connections with any of them, leading to stress and illness. If we had few enough encounters that we could come to recognize most of them, it would build trust and a sense of community.