Could have told you that - cities

Always has been a link. Here, here, here, here and here for starters. From United Press International:

Adults at risk for mental health disorders drawn to city living, study finds
People genetically predisposed to mental health disorders such as schizophrenia, bipolar disorder and anorexia nervosa prefer to live in urban areas as adults, a study published Wednesday by JAMA Psychiatry found.

Those with higher genetic risk for these disorders were 5% to 10% more likely to "preferentially move" from rural to urban areas as adults, the data showed.

This means that people with more genetic mutations who increase their risk for mental health problems are drawn to urban environments, which is significant, given that city-living long has been associated with increased risk for schizophrenia, the researchers said.

Not healthy.