In the Journals

Environmental risk factors associated with ADHD risk

New study findings from Australia suggest there may be maternal, pregnancy and newborn risk factors associated with attention-deficit/hyperactivity disorder.

The risk for ADHD is increased with smoking during pregnancy, maternal urinary tract infections, being induced, and experiencing threatened preterm labor, according to the study results published in Pediatrics.

“It is important that mother recognize the risk of ADHD associated with smoking in pregnancy and the small increased risk with prematurity,” Desiree Silva, MB, BS, FRACP, MPH, of the Telethon Institute for Child Health Research in Australia, told Infectious Diseases in Children. “Attention to maternal infections and preeclampsia may also reduce this risk.”

Desiree Silva

Silva and colleagues evaluated 12,991 non-Aboriginal children and adolescents born in Western Australia younger than 25 years diagnosed with ADHD and prescribed stimulant medication to determine maternal, pregnancy and newborn risk factors. All participants were chosen from the Midwives Notification System, including 30,071 children in the control group.

Participants with ADHD were more likely to have mothers who were younger, single and smoked during their pregnancy. The mothers also were more likely to have had threatened preterm birth before 37 weeks for both boys (OR=2.46; 95% CI, 1.73-3.51) and girls (OR=2.09; 95% CI, 0.9-4.85). There also was an increased risk for ADHD for boys (OR=1.37; 95% CI, 1.21-1.55) and girls (OR=1.51; 95% CI, 1.21-1.9) when the mother had a urinary tract infection during pregnancy.

Boys (OR=1.32; 95% CI, 1.21-1.44) and girls (1.44; 95% CI, 1.22-1.7) also had an increased risk for ADHD when their mothers had preeclampsia during pregnancy. However, oxytocin augmentation had a protective effect on female births (OR=0.58; 95% CI, 0.34-0.98).

“Our study is one of the largest population studies on antenatal risk factors published to date, using a robust, reliable data linkage system with only de-identified data, ensuring strict privacy,” the researchers wrote. “Importantly, we found that risk associations were generally similar for boys and girls with ADHD. We did not confirm an elevated risk for a number of previously published prenatal, pregnancy and postnatal factors. However, the risk of ADHD remained elevated in children exposed to maternal smoking, preeclampsia, maternal UTIs, induced labor, and early term deliveries, irrespective of gender.” — Amber Cox

Desiree Silva, MB, BS, FRACP, MPH, can be reached at

Disclosure: The study was funded by a grant and fellowship from the National Health and Medical Research Council Program Grant and Australian Research Council Linkage Grant. The study authors report no relevant financial disclosures.