Birth Seasonality of Schizophrenia and Bipolar Disorder? A Review of Inpatient Records.

Background: Numerous studies on seasonality of birth for mood disorders and schizophrenia have been published but findings are inconsistent . We aim to test the hypothesis of lack of seasonal birth differences in hospitalized Bipolar Disorder and Schizophrenia patients.

Methods: 15969 inpatient records in UTHealth Harris County Psychiatric Center between 2012-2014 were enrolled (HSC-MS-14-0274). Patients birth months that were diagnosed as Schizophrenia (n=4178) and Bipolar Disorder (n=5303) according to the DSM IV Criteria were tabulated including admitting diagnosis. Texas Birth statistics between 1903-1997 were obtained as control group (n= 17096471).

Results: There was no significant difference for winter births between schizophrenia patients and control group (P=0.738) and there was no significant difference for winter births between bipolar patients and control group either (P= 0.862). Mann Kendall Trend Analysis showed no significant trends of birth months for schizophrenia, bipolar and control groups.

Limitations: The study limitations include being a retrospective study, inability to control for environmental factors, and recruiting from a single location.

Conclusions: Our large sample showed no association between birth season or months with schizophrenia or bipolar disorder. Severe schizophrenia that requires admission may not be related with birth seasonality.