Psychotic illness after prenatal exposure to the 1953 Dutch Flood Disaster

We tested the hypothesis that maternal stress during pregnancy increases the risk of non-affective psychosis for the child. The concept of non- affective psychosis includes the ICD categories schizophrenic disorder, paranoid state and other non-organic psychosis. Data from the Dutch Psychiatric Registry were examined for an effect of the Flood Disaster of 1 February 1953. On this day, a gale caused a flood in the South-west of The Netherlands and 1835 people perished. Our study concerned the 19 villages where mortality exceeded 0.25%. The risk of non-affective psychosis for the cohort born in the period February-October 1953 was compared to the risks for the cohorts born in the corresponding periods of the previous and subsequent 2 years. The relative risk of non-affective psychosis for those exposed during gestation was 1.8 [95% Confidence Interval (CI): 0.9-3.5]. Thus, our study failed to demonstrate a significant association between prenatal exposure to maternal stress and risk of non-affective psychosis. The possible explanations for this finding are discussed.