Prevalences of Anorexia, Autism, and Schizophrenia, Are Strongly Associated With Average Annual Temperatures: Systematic Review and Linear Regression Analysis.

BACKGROUND: The impact of potential environmental influences, like temperature changes and latitudinal gradient, has not been investigated in depth in psychiatric diseases. The aim of this project was to investigate the association of geographical latitude and temperature with the prevalence of psychiatric disorders. METHODS: Linear regression analysis was performed for 201 countries by analyzing average annual temperatures and age-standardized rates (prevalence) of seven major psychiatric entities. A systematic review was also performed, investigating if these correlation data were supported by published original studies. RESULTS: Linear regression analysis showed a significant correlation between average annual temperatures and age-standardized rates (p < 0.0001) for three psychiatric disorders: anorexia, autism, and schizophrenia. Systematic review analysis showed that the prevalence of autism and schizophrenia is potentially influenced by geographic and climatic factors. However, no published data were identified to support the findings for anorexia. CONCLUSION: These preliminary findings underscore the complexity of interactions between environmental, genetic, and socioeconomic factors for psychiatric diseases. The association between temperature and prevalence of psychiatric diseases needs further investigation to reveal any unknown epidemiological factors that contribute to disease pathogenesis.