Uploaded August 2026 | Updated September 2026, 2 weeks ago
Does birth order affect ADHD risk? New research says that first-born siblings in families with two children are more likely to develop ADHD and autism, plus other conditions such as allergies, asthma, and acne. Second-borns showed higher rates of migraines, stomach issues, and substance use disorder.
Scientists studied more than 10 million individuals for one of the largest birth order studies yet. But the data doesn’t tell the whole story. Being the older or younger of two doesn’t necessarily cause these conditions. What the data may reflect is the different environments siblings grow up in.
Does this track for you?
Read the full study here: nature.com/articles/s44360-026-00177-z
Does birth order affect ADHD risk? New research says that first-born siblings in families with two children are more likely to develop ADHD and autism, plus other conditions such as allergies, asthma, and acne. Second-borns showed higher rates of migraines, stomach issues, and substance use disorder.
Scientists studied more than 10 million individuals for one of the largest birth order studies yet. But the data doesn’t tell the whole story. Being the older or younger of two doesn’t necessarily cause these conditions. What the data may reflect is the different environments siblings grow up in.
Does this track for you?
Read the full study here: nature.com/articles/s44360-026-00177-z
