Miller M, et al. - Using data obtained from medical records of 2 large health care systems in the US, researchers examined the risk of sibling recurrence and sibling cross-aggregation of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in children with either disorder who were later born. The findings suggested that later-born siblings of ASD or ADHD children seem to be at a high risk for the same disorder, but also for the other disorder. They advised that later-born siblings of children with ADHD or ASD for both conditions should be monitored. In later-born siblings of children with ASD or ADHD, specialists may want to share this information with families given the potential relevance of monitoring social communication, attention, and behavior regulation skills.

Methods

• In this study, estimates of recurrence risk and cross-aggregation in later-born siblings of ADHD or ASD children were compared with later-born siblings of children without these diagnoses.
• One data set included children between January 1, 1995 and December 31, 2013, while the other data included children born between January 1, 1998 and May 17, 2010.
• Participants in the study were 15,175 later-born siblings of children with ADHD, ASD, and no known diagnosis.
• The study was carried out between October 2, 2017 and August 14, 2018.
• The primary outcomes of interest were the diagnoses of ASD or ADHD in the later-born sibling, ascertained from medical records.
• Moderators included sex, gestational age, and maternal age.

Results

• In total, 15,175 later-born siblings were classified by familial risk status based on the diagnostic status of the older child: ADHD risk (n = 730; male [51.92%]), ASD risk (n = 158; male [48.10%]), and no known risk (n = 14 287; male [50.73%]).
• Later-born siblings of children with ASD were more likely to be diagnosed with ASD (odds ratio [OR], 30.38; 95% CI, 17.73-52.06) or ADHD in the absence of ASD (OR, 3.70; 95% CI, 1.67-8.21) vs later-born siblings of children without ADHD or ASD.
• Later-born siblings of children with ADHD were more likely to be diagnosed with ADHD (OR, 13.05; 95% CI, 9.86-17.27) or ASD in the absence of ADHD (OR, 4.35; 95% CI, 2.43-7.79) vs later-born siblings of children without a diagnosis.