Schizophrenia may be linked to deprivation after research showed higher concentrations of the disease in poor urban areas with high population density.
Researchers at the University of Cambridge and the Queen Mary University in London analysed 427 people with schizophrenia between the ages of 18 and 64.
They found that there were higher rates of the disease in urban areas linked with deprivation and inequality.
Researchers assessed the social environment by measuring the neighbourhood they lived in at the onset of the disease.
The incidence of schizophrenia was increased by three environmental risk factors: increased deprivation, increased population density and increased inequality.
Results, published in the journal Schizophrenia Bulletin, suggest that people living in poorer areas were four per cent more likely to develop the disease.
In the UK, schizophrenia affects around 40,000 adults in England and around 24 million worldwide.
A recent report by the Schizophrenia Commission found the care for people with the disease is failing catastrophically and that many patients with severe psychosis spend time in hospitals that have become "frightening places".
Inequality in Western societies increasing
The latest findings offer further evidence that inequality is linked to health. Lead author James Kirkbride, said: "Inequality seems to be important in affecting many health outcomes, now possibly including serious mental illness ... both absolute and relative levels of deprivation predict the incidence of schizophrenia."
Peter Kinderman, chartered psychologist from the University of Liverpool, added: "Like many other similar pieces of research, it confirms that social, economic and psychological factors are important causes of many mental health problems - even problems as serious as those leading to a diagnosis of schizophrenia.
"Many people seem to believe that all mental health problems - and perhaps especially schizophrenia - are simply brain diseases. Instead, research such as this clearly demonstrates that social causes are crucial and are key elements of helping people too.
"The fact that inequity is linked to a diagnosis of schizophrenia is particularly striking. Inequalities in many Western societies are acute and rising, especially in our current economic crisis.
"We need to understand that our mental health is not merely a biological phenomenon, but is much more a product of how people make sense of their world. And this, in turn, is affected by social, economic and political decisions."
Dr John Williams, head of neuroscience and mental health at the Wellcome Trust said: "This research reminds us that we must understand the complex societal factors as well as the neural mechanisms that underpin the onset of mental illness, if we are to develop appropriate interventions."