Birth order affects ADHD risk

By Wayne Kuznar, for MDLinx
Published June 1, 2018

Key Takeaways

The risk of attention deficit hyperactivity disorder (ADHD) increases for firstborn children compared with the youngest born and single children, according to a German study published in the Journal of Attention Disorders. In addition, the risk for ADHD increases with the number of younger siblings of a firstborn child.

The authors state the findings provide evidence that birth order plays a role in ADHD and should be considered during diagnosis and treatment.

“Professionals might benefit from focusing more intensively on the subjective meaning of having younger siblings, for example, regarding individual etiology models when treating ADHD,” they wrote.

Previous studies examining birth order and the risk of ADHD have produced inconsistent results.

The authors of the current study, led by Charlotte Reimelt, Technische Universität, Dresden, Germany, used the German National Health Interview and Examination Survey for Children and Adolescents study to examine factors for the occurrence of ADHD in children and adolescents. The analysis included 13,488 children between 3 and 17 years of age, including 660 children who had been diagnosed with ADHD. Within the ADHD group, 79.8% were male, whereas 48.5% of the children and adolescents in the non-ADHD group were male.

A higher risk for ADHD was found in firstborn children with siblings compared with children without a sibling (single child; OR: 1.31, 95% CI: 1.03-1.68). The higher risk in firstborn children was confirmed when firstborn children were compared with youngest born children in families with siblings (more than one child; OR: 1.31, 95% CI: 1.09-1.58).

The higher risk of ADHD in firstborn children remained significant after controlling for potential confounders that were associated with ADHD, such as children’s age and gender, socioeconomic status, maternal age at childbirth, low birth weight/premature birth, and duration of breastfeeding. Firstborn children had a higher risk for ADHD when compared with single children (OR: 1.55, 95% CI: 1.09-2.21) and when compared with youngest born children within the group of children with siblings only (OR: 1.37, 95% CI: 1.06-1.76).

After controlling for confounders, the risk for ADHD was 1.52-times higher in firstborn children with one younger sibling (95% CI: 1.05-2.19) when compared with single children, and 1.71-times higher in firstborn children with two or more younger siblings (95% CI: 1.08-2.69) when compared with single children.

“This indicates that the risk for ADHD in firstborn children increases with the number of younger siblings,” the authors wrote.

The results are comparable with two previous studies that also reported an increased risk for ADHD in firstborn children. These studies either did not control for other common ADHD risk factors1 or controlled only for sex2, the researchers noted.

The findings of the current study suggest that changes to the family structure that a firstborn child must address when younger siblings arrive, as well as the number of younger siblings, play an important role regarding the risk for ADHD in firstborn children.

To read more about this study, click here


  1. Carballo JJ, et al. Soc Psychiatry Psychiatr Epidemiol. 2013;48(8):1327-1333.
  2. Marin AM, et al. J Atten Disord. 2014;18(7):594-597.
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