The observation that higher rates of schizophrenia and other nonaffective psychotic disorders are associated with city living is robustly replicated across epidemiologic studies conducted throughout Northern Europe and North America. The weight of this evidence, combined with exhaustive investigations of potential bias, suggest that methodological artifacts are unlikely to explain such associations. Instead, they imply a causal role for underlying environmental factors more common in urban settings. Evidence from northern Europe strongly links social factors, including deprivation, inequality, and social isolation, to raised rates of nonaffective psychotic disorders in urban settings, and while mechanisms through which such factors influence psychosis remain uncharacterized, they may include effects of social stress and possibly exposure to socially distributed biological factors, such as poor nutrition, infections, and/or pollutants.
James B. Kirkbride, PhD; Katherine M. Keyes, PhD; Ezra Susser, MD, DrPH
JAMA Psychiatry, October 10, 2018