Big Cities Blues Buster

 With regard to depression, the most important insight is that larger cities facilitate more social interactions. And yes, this too follows the 12 per cent rule. To ground this in some hypothetical numbers, if residents of a city of 1 million people averaged 43 social contacts within the same city, then residents of a city of 10 million people would be expected to average 63 social contacts. Why is this important for depression? For about 10 years, we have known that the number of social contacts people have is strongly associated with the risk for depression: the more people you interact with, the lower your risk of experiencing depressive symptoms. Given this, it makes sense that we have found that depression rates are lower in larger cities, and that this reduction in depression rates follows the 12 per cent rule.

https://psyche.co/ideas/why-life-is-faster-but-depression-is-lower-in-bigger-cities