Sibship size, birth order and psychotic experiences: Evidence from 43 low- and middle-income countries

Ai Koyanagi, Hans Oh, Andrew Stickley, Brendon Stubbs, Nicola Veronese, Davy Vancampfort, Josep Maria Haro, Jordan E. DeVylder

Research output: Contribution to journalArticlepeer-review


Background: Sibship size and birth order may be contributing factors to the multifactorial etiology of psychosis. Specifically, several studies have shown that sibship size and birth order are associated with schizophrenia. However, there are no studies on their association with psychotic experiences (PE). Methods: Cross-sectional, community-based data from 43 low- and middle-income countries which participated in the World Health Survey were analyzed. The Composite International Diagnostic Interview was used to identify four types of past 12-month PE. The association of sibship size and birth order with PE was assessed with multivariable logistic regression. Results: The final sample consisted of 212,920 adults [mean (SD) age 38.1 (16.0) years; 50.7% females]. In the multivariable analysis, compared to individuals with no siblings, the OR increased linearly from 1.26 (95%CI = 1.01–1.56) to 1.72 (95%CI = 1.41–2.09) among those with 1 and ≥ 9 siblings, respectively. Compared to the first-born, middle-born individuals were more likely to have PE when having a very high number of siblings (i.e. ≥9). Conclusions: Future studies should examine the environmental and biological factors underlying the association between sibship size/birth order and PE. Specifically, it may be important to examine the unmeasured factors, such as childhood infections and adversities that may be related to both family structure and PE.

Original languageEnglish (US)
Pages (from-to)406-412
Number of pages7
JournalSchizophrenia Research
StatePublished - Nov 2018


  • Birth order
  • Psychotic experience
  • Risk factor
  • Sibship size

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Biological Psychiatry


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