(June 14, 2016) Multiple studies have found that growing up in a city doubles the risk of developing schizophrenia or other psychotic disorders in adulthood. Research also has found that children who experience psychosis are at significantly higher risk for developing schizophrenia and other mental health disorders as adults.
Given the personal and economic toll of psychiatric diseases and the fact that two-thirds of the world's population is projected to be living in cities by 2015, the question of "Why?" urbanicity is associated with psychosis is an urgent one.
Childhood Psychosis "Surprisingly Prevalent"
In search of answers, a team of researchers from King's College in London and Duke University in North Carolina analyzed the neighborhood characteristics of more than 2,200 12-year-olds participating in a longitudinal twin study in Great Britain. An advance report on the team's findings was published May 6 in Schizophrenia Bulletin online ("Why are children in urban neighborhoods at increased risk for psychotic symptoms? Findings from a UK longitudinal cohort study").
Joanne Newbury and colleagues note that psychotic symptoms are "surprisingly prevalent" among children in the general population. Although such symptoms typically are short-lived, children who experience them are at "significantly elevated risk" for schizophrenia and other psychotic and mental health conditions as adults, including substance abuse, depression, post-traumatic stress and suicidal behavior. The authors said the trajectory is "consistent with the neurodevelopmental model of schizophrenia," which holds that serious psychiatric disease begins developing at the neurological level during childhood or early adolescence, long before symptoms are manifest.
The participant twins were equally likely to be living in urban or suburban/small town/rural settings. At the age of 12, 5.9% of the 2,232 children reported experiencing at least one psychotic symptom (e.g., hallucinations, paranoid delusions). However, city children were 80% more likely to have experienced symptoms: 7.4% of the urban-dwelling children compared 4.4% of the non-urban children.
The pattern held true independent of family socioeconomic status, psychiatric history, maternal psychosis and/or whether the neighborhood was affluent or economically deprived. The same association was not found between urbanicity and depression or anxiety.
Risk and Mitigation Factors
The study analyzed four neighborhood social characteristics for their potential role in the association: social cohesiveness and supportiveness among neighbors; social control, including the likelihood of neighbors intervening in neighborhood problems; neighborhood disorder, whether physical or social; and direct experiences of being victimized (e.g., mugged).
Children who lived in neighborhoods with higher social cohesion and social control at the age of 5 were "significantly less likely to experience psychotic symptoms" at the age of 12, the analysis found, while children living in neighborhoods with higher levels of disorder and crime victimization at 5 years old were "significantly more likely" to experience psychotic symptoms by the age of 12. Low social cohesion combined with crime victimization explained nearly 25% of the association between urbanicity and psychosis in childhood.
"From a child's perspective, growing up in a crowded neighborhood characterized by insecure/ nonexistent social support networks, unfriendly/unpredictable interactions between neighbors, and fear of/ exposure to crime could promote psychotic symptoms in various mutually compatible ways," according to the authors.
The researchers speculated that prolonged exposure to neighborhood-level social stressors "could dysregulate the hypothalamic-pituitary-adrenal axis, dopaminergic system and/or neurodevelopment" to increase risk of psychotic symptoms, particularly among children with a genetic predisposition, but these possible mechanisms were beyond the scope of the study.
"The present findings therefore underscore the emerging need to identify the social, psychological and biological pathways leading from neighborhood-level exposures to childhood psychotic symptoms," the authors concluded - and, by extension, into adult schizophrenia and other serious mental illness.
"Urbanicity," they said, "is a key area for psychosis research."
Doris A. Fuller
Chief of Research and Public Affairs
References:
- Newbury, J. et al. (6 May, 2016). "Why are children in urban neighborhoods at increased risk for psychotic symptoms? Findings from a UK longitudinal cohort study." Schizophrenia Bulletin.
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