Preterm and low–birth-weight births have been thought to be risk factors for the development of ADHD. A recent meta-analysis now sheds light on the magnitude of the association.1
A review of cross-sectional, prospective, and retrospective studies—conducted by a multicenter team of Brazilian researchers—showed that children who were very premature or otherwise had very low birth weight had a 2-fold increased risk of ADHD diagnosis and symptomatology compared with children of normal gestation and birth weight (odds ratio [OR] = 2.25 [95% confidence interval (CI), 1.56-3.26]). Risk was more pronounced for children who were extremely preterm or had extremely low birth weight. (OR = 4.05 [95% CI, 2.38-6.87]).
The team acknowledged that the cause of ADHD is complex and not fully understood; it consists of a multifactorial interplay of genetic and nonheritable factors. They reviewed studies of children, adolescents, and adults that assessed ADHD diagnoses in relation to very or extremely premature births and/or very low or extremely low weight births against controls born near or at normal birth weight (≥ 5.5 lb) or near, at, or more than 37 weeks’ gestational age. Very premature was defined as gestational age < 32 weeks, and very low birth weight was defined as < 3.3 lb, and extremely premature and extremely low birth weight were defined as higher degrees of prematurity (< 28 weeks) or low birth weight (< 2.2 lb), respectively. Study subjects must have had an ADHD diagnosis established via DSM-III criteria.
Of 519 studies identified, 34 met inclusion criteria and were included in the final analysis. Twelve of these studies, inclusive of 1787 subjects, were included in a categorical diagnosis analysis, and 29 studies, inclusive of 3504 subjects, were included in an analysis of ADHD symptomatology.
ADHD risk was confirmed to be higher in persons who were born very or extremely premature and/or were of very low or extremely low birth weight, with an OR that was 3.04 higher than controls (95% CI, 2.19-4.21). The more extreme the prematurity or low birth weight, the higher the OR. That is, persons who were born very/extreme premature and of very/extremely low weight were about 3 times more likely to receive an ADHD diagnosis than those who had term, normal-weight births. Whereas the risk was doubled in the very premature/low birth weight, it was quadrupled in the extremely premature/low birth weight.
Analysis of ADHD symptomatology found significant associations between prematurity/low birth weight and inattention (standardized mean difference [SMD] = 1.31 [95% CI, 0.66-1.96]), hyperactivity and impulsivity (SMD = 0.74 [95% CI, 0.35-1.13]), and combined symptoms (SMD = 0.55 [95% CI, 0.42-0.68]) versus controls (all P < .01).
The bottom line
In light of these findings, the researchers recommend that specific neonatal, pediatric, and psychiatric interventions be applied to prevent and minimize ADHD symptomatology in premature and low–birth-weight infants. They call for further research to clarify the specifics of the association between ADHD and prematurity/low birth weight.
1. Franz AP, Bolat GU, Bolat H, et al. Attention-deficit/hyperactivity disorder and very preterm/very low birth weight: a meta-analysis. Pediatrics. 2017 Dec 18. [Epub ahead of print]