New research suggests there’s a link between genetic risk for psychiatric disorders and the likelihood of living in a city.
Previous studies argue that the stress of living in a city, along with exposure to elements like pollution, is a risk factor for mental health conditions like schizophrenia. Cities are typically associated with higher rates of mental health problems — the why, however, is up for debate.
In a study published in October in the journal JAMA Psychiatry, researchers find one’s genetic risk for mental health conditions can influence where a person chooses to live. This isn’t to say that environment doesn’t play a role in the development of mental health conditions. Instead, the study team calls for more integrated approaches when it comes to exploring, and addressing, what causes these conditions — therapeutic steps that consider all the factors that result in a diagnosis.
Critically, carrying this genetic risk doesn’t mean a person has a mental health condition — and the majority of individuals in the 385,793 person sample did not have a diagnosis. Overall, when the research team compared people who moved from rural areas to urban areas to those who stayed in rural areas, they found higher genetic risks for autism, anorexia, bipolar disorder, and schizophrenia. Meanwhile, they found a lower genetic risk for ADHD.
Jonathan Coleman is a co-author of this study and a lecturer at King’s College London. He tells Inverse this research doesn’t negate the adverse effects of living in cities on mental health, but instead “supports the idea that people with a greater genetic predisposition to worse mental health are also more likely to move to cities.”
“We would say our research shows that the influences on mental health are nuanced,” Coleman says. “Both environmental and genetic factors may have important effects, and we need to take an integrated approach to understand these effects.”
The link between genes and where you live
Coleman and colleagues examined genetic data pulled from people between the ages of 37 and 73 who participated in the UK Biobank project.
This study is based on a specific population. Because cities, and the reason people choose to live in cities, are different all over the world, “there are good reasons to think that the genetic and environmental influences of cities on mental health may vary between.”
The team calculated the polygenetic risk score for each participant for various mental health conditions. A polygenetic risk score is a measurement of disease risk based on a person’s genes — it’s an estimation and most people have some level of genetic risk for mental health conditions.
The scores were compared to data associated to:
- Where the study participants live
- Where they’ve moved
- The population density of these places, based on UK census data
Overall, the study team writes, these “findings suggest a high genetic risk for a variety of psychiatric disorders may affect an individual’s choice of residence.”
Mental health and why people move — “Where an individual lives is obviously a highly complex matter, influenced both by things within their control and things outside of their control,” Coleman says.
You may move to a city to seek further education, to be closer to better healthcare, or because you got a new job. And while many of these elements have been found to be related to genetics, DNA is only one part of the recipe. Genes can inform a framework for how one behaves, but one’s environment is arguably what determines the actual result.
Moving to cities, Coleman points out, may also with it some degree of risk because genetic influences on risk-taking could influence that decision. “Overall, there are lots of different contributing factors to moving to a city,” he says, “and many of those may be influenced in part by genetic variation.”
Seemingly confounding the situation, alongside studies that find urban dwellers are more likely to develop mental health conditions, are other studies that suggest cities can actually benefit mental health because cities provide the sort of social interactions that help mental health.
So, what exactly is going on? Ultimately, research like the kind displayed in the JAMA Psychiatry study suggests there’s more to this link between genes and urban living than we previously realized — and it’s something to probe if we really want to get better at providing much-needed mental health support.
That understanding can be incorporated into this wider understanding that physical and social factors influence mental health too.