Month of birth and mental disorders: A population-based study and validation using global meta-analysis

Area of Science:

• Psychiatry
• Epidemiology
• Genetics

Background:

• Month of birth (MOB) has been linked to certain mental disorders (MDs).
• However, the extent of this association across all MDs remains incompletely understood.
• Investigating MOB's role is crucial for understanding MD etiology.

Purpose of the Study:

• To investigate the association between month of birth and a comprehensive range of mental disorders.
• To determine if specific birth seasons correlate with increased risks for various MDs.
• To provide a population-based and meta-analytic reference for future etiological research.

Main Methods:

• A population-based cohort study of 1,951,777 patients in Taiwan examined 34 DSM-5 mental disorders.
• Relative risk ratios (RR) for each disorder by month of birth were calculated.
• A meta-analysis of 51 studies (10 MDs) was conducted, pooling RRs and assessing birth season effects.

Main Results:

• Most mental disorders showed significant month of birth periodicity, excluding PTSD, dissociative disorders, feeding/eating disorders, gender dysphoria, and paraphilic disorders.
• Winter births were associated with higher risks of schizophrenia, bipolar I disorder, and major depressive disorder.
• Youngest age at school entry (due to MOB) correlated with increased risks for intellectual disability, autism, and attention-deficit/hyperactivity disorder.

Conclusions:

• Month of birth is demonstrably related to the risk of developing specific mental disorders.
• These findings highlight the importance of birth timing in the multifactorial etiology of mental health conditions.
• The study offers valuable insights for future research into the developmental origins of mental disorders.