Being First or Second Born Could Determine What Diseases You Develop
Researchers found that the illnesses first born children and second born children are diagnosed with tend to differ.
Being the first or second child in a family may influence the types of diseases one is more likely to develop, according to a comprehensive new study. Researchers examined health records from over 10 million individuals across 5.1 million U.S. families and discovered significant birth-order associations for more than 150 diseases.
The study, published in Nature Health, identified several conditions where the first-born and second-born children experienced notable differences in diagnosis rates. Among neurodevelopmental disorders, first-born children were more likely to be diagnosed with autism, ADHD, Tourette's syndrome, and obsessive-compulsive disorder.
Second-born children, however, had about 43% lower odds of being diagnosed with other pervasive developmental disorders and also showed reduced rates of autism. Besides autism, second-born children were more likely to develop substance abuse disorders, migraines, gastritis, biliary tract disease, kidney infections, and herpes zoster (shingles).
Researchers found the strongest links between birth order and neurodevelopmental and allergy-related conditions. The study's lead author, Andrey Rzhetsky of the University of Chicago, noted that the unexpected findings, including the large effect of herpes zoster and the nearly even distribution of outcomes between first-born and second-born children, suggest a complex interplay of biological, environmental, and social factors.
While the study does not establish causation, it provides valuable insights into the potential impact of birth order on disease risk and highlights the need for further research into these mechanisms.
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