Country and Rural life (vs. city living) before age 15 is associated with lower rates of schizophrenia

Researchers have found a positive correlation between rural birth, and living conditions and lower rates of schizophrenia. In fact, a number of studies have demonstrated that psychotic illness is more prevalent in urban settings than in rural areas. Why this potential connection exists is unclear, but higher rate in urban areas may be due to environmental toxins, the social context that people live in, and viruses or influenza, including prenatal infections. Where you are born and brought up is a larger contributing factor to risk than genetic predisposition.

In the past 10 years, major birth cohort studies in developed countries have revealed that the incidence of schizophrenia is about 2 times higher among people in cities, reported Dr. Ezra Susser, head of epidemiology at Columbia University's Mailman School of Public Health.

"It's not clear if it is birth in cities, or upbringing in cities, but there is something about city living that increases risk," he said. Where you are born and brought up is a larger contributing factor to risk than genetic predisposition. Indeed, 34.6% of schizophrenia cases would be prevented if people were not born and brought up in cities, compared to 5.4% of cases that would be prevented if people did not have parents or siblings who suffered from the illness, Susser told participants at the New York conference (2004).

Moreover, there is a clear dose-response relationship for "urbanicity" - in that the larger the town of birth, the greater the risk of schizophrenia. This dose-reponse relationship suggests that causal factors are of an ongoing or repeated nature are operating in urbanized environment.

A recent study of 4.4 million men and women in Sweden found a 68%–77% increased risk of psychosis (a broader term that includes schizophrenia) for people living in the most urbanized environments, a significant proportion of which is likely to be accounted for by people who have schizophrenia (Source: Urbanisation and incidence of psychosis and depression: Follow-up study of 4.4 million women and men in Sweden. British Journal of Psychiatry)

Preben Mortensen, M.D., a professor of psychiatry at Aarhus University in Taasingegade, Denmark, and colleagues have found the more time a person spends before the age of 15 in an urban area, the higher his or her risk of developing schizophrenia. Those researchers speculated that people born in urban areas are exposed to more infections during prenatal development and childhood. Some experts believe early exposure to infections may affect the developing brain in a way that makes it more vulnerable to schizophrenia. Other experts have suggested that in high density urban environments there is higher likelyhood of social stress and social adversity (bullying, etc.) as well as lower income levels, and poorer educational systems. Additionally, leaded gasoline has been implicated as a factor in causing brain damage and increased risk of schizophrenia.

Interestingly - being in a very isolated rural area is also a factor that has been identified as increasing the risk of schizophrenia. This relates to the "social isolation" factor that has also been identified as something that increases the risk of schizophrenia. In 1956 Dr. Hare reported that social isolation, as measured by single person households in a geographical area, was associated with increased rates of schizophrenia. In 1993, Dr. Thornicroft noted that clustering of individual cases of schizophrenia in deprived areas of the city occurs only in urban areas and suggested that social isolation is an important mediator in this (while other researchers note that its difficult to separate cause and effect in this research). In 2000, Dr. Van Os found that people who were single had a slightly higher risk of developing psychosis if they lived in a neighborhood with fewer single people compared with a neighborhood with many other single people.

Action: Living outside a city before age 15 may reduce your chances of getting schizophrenia. If you do live in an urban area, try to maintain an active social network, a healthy diet, and a low-stress lifestyle (all of which have been shown to reduce schizophrenia risk) for you and/or or your children. Avoid excessive exposure to viruses while pregnant, and toxins such as lead. Maintain a healthy, low stress family life.

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