Evidence that childhood urban environment is associated with blunted stress reactivity across groups of patients with psychosis, relatives of patients and controls

Psychosis is associated with urban upbringing, and increased emotional reactivity is associated with psychosis. The aim of this study was to examine to what degree urban upbringing impacts emotional reactivity, and how this may be relevant for psychotic disorder and familial risk of psychotic disorder. Patients with a diagnosis of non-affective psychotic disorder (n = 57), 59 first degree relatives of patients and 75 healthy comparison subjects were studied with the experience sampling method (a random time sampling technique to assess affective experience in relation to fluctuating stressors in the flow of daily life), to measure a change in negative affect in relation to subjective stress. Urban exposure was defined at 5 levels, considering the population density and the number of moves between birth and the 15th birthday, using data from the Dutch Central Bureau of Statistics and the equivalent database in Belgium. Multilevel random regression analyses showed that urban upbringing was consistently and strongly associated with a reduced increase in negative affect in relation to SS in adulthood in a dose-response fashion in all three groups. Regression coefficients in the patient group decreased from 0.148 (p <0.001) in the lowest urbanicity level to 0.094 (p <0.001) in the highest urbanicity level. The findings suggest that urban upbringing may occasion "habituation" rather than "sensitization" across groups, which may or may not be relevant for the onset of psychotic disorder.