Protective Effect of Being Born in Autumn Against Schizophrenia or Schizoaffective Disorder

Objective: Birth season, one of the environmental factors in the etiology of schizophrenia, has been considered as a risk factor and various studies have been conducted. Some studies on the relationship between season of birth and schizophrenia have emphasized that, while being born in winter is a risk factor, being born in summer and autumn should be investigated as a protective factor. The aim of our study is to determine whether being born in autumn is a protective factor for being diagnosed with schizophrenia/schizoaffective disorder. Method: It was aimed to determine the relationship between the diagnosis of schizophrenia or schizoaffective disorder and the season of birth by comparing the seasons of 832 patients diagnosed with schizophrenia or schizoaffective disorder who were admitted to Trakya University Faculty of Medicine psychiatry outpatient clinics or hospitalized in the psychiatric clinic between 2005 and 2023, with 17.360.594 live births that took place in Turkey since 2009. Result: Season (p=0.018) and gender (p<0.001) variables showed a statistically significant difference between the patient and control groups. When being born in autumn is taken as a reference, it has been determined that being born in winter increases the risk of being diagnosed with schizophrenia or schizoaffective disorder by 1.36 times (p=0.001), being born in spring by 1.25 times (p=0.014), being born in summer by 1.18 times (p=0.045) and using being female as a reference, being born as male increases the risk of being diagnosed with schizophrenia or schizoaffective disorder by 1.32 times (p<0.001). Conclusion: According to the results of our study, being born in winter is a risk factor for being diagnosed with schizophrenia-schizoaffective disorder, while being born in autumn is a protective risk factor for being diagnosed with schizophrenia-schizoaffective disorder.