Overview

• Researchers tracked over one million Norwegians born from 1991 to 2012 through national health registries assessing psychiatric diagnoses from ages 4 to 17.
• Children born in October through December are diagnosed with mental health disorders more often than their older classmates.
• ADHD rates rise by 20–80 percent for the youngest cohort members depending on term status.
• Late-year births also show increases in other neuropsychiatric disorders with delays spanning language, academic skills, motor development.
• The youngest premature girls face significantly higher risks of anxiety, depression, adaptation disorders compared with their oldest peers.