An association between autumn birth and clozapine treatment in patients with schizophrenia: A population-based analysis

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

  • Holger Jelling Sørensen, Aalborg University, Denmark
  • Leslie Foldager
  • Rasmus Røge, Aalborg University, Denmark
  • Sofie Gry Pristed, Aalborg University, Denmark
  • Jesper T. Andreasen, University of Copenhagen, Denmark
  • Jimmi Nielsen, Aalborg University, Denmark

Background: Numerous studies on seasonality of birth and schizophrenia risk have been published but it is uncertain whether, among those with schizophrenia, refractory illness exhibits any predilection for birth month. We hypothesized and examined whether a season of birth effect was present in patients with schizophrenia with a history of clozapine treatment.
Method: Using record linkage with Danish registers, we examined patients with schizophrenia born between 1950 and 1970, and between 1995 and 2009 and Cox regression analysis was used to examine season of birth in relation to history of clozapine treatment.
Results: In a study population corresponding to 60,062 person-years from 5328 individuals with schizophrenia of which 1223 (23%) received at least one clozapine prescription, birth in the autumn (September – November) was associated with clozapine treatment (HR 1.24; 95% CI 1.07 – 1.46) when compared with birth in the spring (March – May).
Conclusion: Although replication studies are needed, this is the fi rst evidence from a nationwide study suggesting a possible seasonassociated risk of clozapine treatment in schizophrenia. The reasons for this relationship remain to be further investigated but might be partially explained by early exposures such as winter
flu season and low vitamin D levels.

Original languageEnglish
JournalNordic Journal of Psychiatry
Pages (from-to)428-432
Publication statusPublished - 2014

See relations at Aarhus University Citationformats

ID: 56702767