The results of two new studies suggest that the neighbourhood you live in affects your chance of developing schizophrenia. Surprisingly, neighbourhood seems to have no effect on your risk of bipolar disorder.
The received wisdom says that schizophrenia affects 1% of the population worldwide, with little variation between race, country and area.
These two new studies, led by Dr James Kirkbride, investigated whether street-by-street differences also have an effect.
The research team examined every person who was treated by mental health services in South East London for a first episode of psychosis over a two-year period.
Psychosis involves delusions and hallucinations and most often leads to a diagnosis of schizophrenia or bipolar disorder, bipolar being most associated with mood problems such as soaring highs followed by crashing lows.
South East London is notable for many things, not all of them positive. It’s a high poverty, high crime, highly urbanised inner-city area.
We know that one of the single largest environmental risk factors for schizophrenia is living in an urban area, and, unsurprisingly, this corner of the UK’s captial has one of the highest rates of psychosis in the world.
The team looked at all the areas, and, controlling for the effects of age, sex and ethnicity, used statistics to test whether any differences between areas were likely to due to chance, or whether they varied enough to be confident that the critical influence was the neighbourhood.
The map on the left shows the variation between neighbourhoods. If you know South East London, click on the map to see how it relates to specific areas.
You”ll notice that the toughest, poorest areas tend to have a higher rate of schizophrenia. In comparison, the rates for bipolar disorder were largely the same wherever the team looked.
Even if you don’t know the area at all, the amount of neighbourhood variation is quite startling. In some cases, moving just a few streets could dramatically affect your mental health.
In a second study, the team looked at characteristics of the area to try and see what risk was linked to.
Some main influences stood out: poverty, ethnic fragmentation, and, surprisingly, local election voter turnout.
In fact, a 1% increase in the number of voters in local elections was linked to a 5% reduction in new cases of schizophrenia.
Voter turnout itself is hardly likely to affect mental health, but the researchers suggest it might reflect the sense of community in the neighbourhood: the more you’re concerned about your neighbourhood the more likely you are to vote on issues affecting the area.
Ethnic fragmentation is a measure of how many people of your ethnic background live in your neighbourhood.
Immigrants are known to be at greater risk of schizophrenia than other people in the country, and South East London has a large immigrant population.
This might mean that contact with a community of people who share your cultural experiences may be protective against mental illness, perhaps again suggesting that ‘community spirit’ is key for mental health.
So why do all these things affect schizophrenia and not bipolar disorder? The researchers don’t discuss it in detail probably because it’s a bit puzzling.
The truth, of course, is just outside the front door.
Link to abstract of ‘Neighbourhood variation in the incidence of psychotic disorders in Southeast London’.
Link to abstract of ‘Neighbourhood-level effects on psychoses: re-examining the role of context’.