title: No Evidence of Association between Childhood Urban Environment and Cortical Thinning in Psychotic Disorder.
abstract: The alterations in cortical morphology, such as cortical thinning, observed in psychotic disorder, may be the outcome of interacting genetic and environmental effects. It has been suggested that urban upbringing may represent a proxy environmental effect impacting cortical thickness (CT). Therefore, the current study examined whether the association between group as a proxy genetic variable (patients with psychotic disorder [high genetic risk], healthy siblings of patients [intermediate risk] and healthy control subjects [average risk]) and CT was conditional on different levels of the childhood urban environment and whether this was sex-dependent.
  
  
  
  T1-weighted MRI scans were acquired from 89 patients with a psychotic disorder, 95 non-psychotic siblings of patients with psychotic disorder and 87 healthy control subjects. Freesurfer software was used to measure CT. Developmental urban exposure was classified as low, medium, and high, reflecting 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 regression analyses were used to examine the association between group, sex, and urban upbringing (as well as their interactions) and cortical CT as the dependent variable.
  
  
  
  CT was significantly smaller in the patient group compared to the controls (B = -0.043, p <0.001), but not in the siblings compared to the controls (B = -0.013, p = 0.31). There was no main effect of developmental urbanicity on CT (B = 0.001, p = 0.91). Neither the three-way group × urbanicity × sex interaction (χ2 = 3.73, p = 0.16), nor the two-way group × urbanicity interaction was significant (χ2 = 0.51, p = 0.77).
  
  
  
  The negative association between (familial risk for) psychotic disorder and CT was not moderated by developmental urbanicity, suggesting that reduced CT is not the outcome of familial sensitivity to the proxy environmental factor 'urban upbringing'.
authors.affiliation: Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands.
authors.forename: Aleida
authors.initials: A
authors.lastname: Frissen
authors.affiliation: Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands.|King's College London, King's Health Partners, Department of Psychosis Studies, Institute of Psychiatry, London, United Kingdom.
authors.forename: Jim
authors.initials: J
authors.lastname: van Os
authors.affiliation: Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands.
authors.forename: Petra
authors.initials: P
authors.lastname: Habets
authors.affiliation: Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands.
authors.forename: Ed
authors.initials: E
authors.lastname: Gronenschild
authors.affiliation: Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands.|Institute for Mental Health Care Eindhoven (GGzE), Eindhoven, The Netherlands.
authors.forename: Machteld
authors.initials: M
authors.lastname: Marcelis
mesh_terms: D000293:Adolescent; D000328:Adult; D001530:Belgium / Q000453:epidemiology; D001921:Brain / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D016022:Case-Control Studies; D002947:Cities; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011156:Population Density; D011618:Psychotic Disorders / Q000453:epidemiology* / Q000209:etiology; D012044:Regression Analysis; D012307:Risk Factors; D012720:Severity of Illness Index; D012737:Sex Factors; D035781:Siblings; D012984:Software; D011795:Surveys and Questionnaires; D014505:Urban Population; D055815:Young Adult