Autism Spectrum Disorders and Attention Deficit Hyperactivity Disorder in a Low Birth Weight Cohort: Evidence for a Shared Familial Risk Factor

Autism Spectrum Disorders and Attention Deficit Hyperactivity Disorder in a  Low Birth Weight Cohort: Evidence for  a Shared Familial Risk Factor

Background: Preterm/low birthweight (LBW) infants, who now account for almost 10% of births in the United States, are at excess risk for both ASD and ADHD  Family and twin studies have given rise to the notion that Autism Spectrum Disorders (ASD) and Attention-Deficit Hyperactivity Disorder (ADHD) may have familial risk factors in common.  Within the preterm/LBW population, ASD and ADHD have two established non-familial risk factors in common, namely male gender and perinatal brain injury, but familial risk factors have been less well studied.   A longitudinally followed regional preterm/LBW birth cohort having retrospective data on maternal childhood ADHD symptoms provides an important opportunity to test the hypothesis of shared familial risk for ASD and ADHD,

Objectives: The objective of this study was to determine whether diagnoses of ASD and ADHD but not diagnoses of other psychiatric disorders were associated with maternal recall of ADHD symptoms in their own childhood.    

Methods: This study is based on data from a longitudinal epidemiological study of outcomes in a regional LBW (< 2000 g) cohort (the Central NJ Neonatal Brain Hemorrhage Study, NBHS), born 1984-1987 (N=1105). The entire cohort was screened with neonatal serial head ultrasound for perinatal brain injury.  At the age 16 follow-up, mothers completed (1) the Wender Utah Rating Scale (WURS), a validated measure for the retrospective measurement of childhood ADHD, on themselves (2) a parental report research psychiatric diagnostic interview covering a wide range of DSM IV diagnoses exclusive of ASD, on their adolescent (3) a screen for ASD on their adolescent.  A research diagnostic evaluation of ASD screen positives and a systematic sample of screen negatives was conducted at age 21. Thus, by early adulthood, the NBHS cohort had been assessed for nearly the entire range of DSM IV Axis I diagnoses, including ASD. The twenty-five items on the WURS that have been shown to discriminate between adults with ADHD and controls were used here to derive a total score.

 Results: The table below shows the WURS scores in relation the three diagnostic groups of interest. 

Wender 25-Item Total Scores by ASD, ADHD,  and Any Other Diagnosis
Diagnoses	Positive for Diagnosis		Negative for Diagnosis		Difference	P-values
	N	Mean (± SD)	N	Mean (± SD)	Unadjusted	Adjusted
ASDa	13	21.23 (±15.78)	169	11.23 (±11.77)	.005	.004
ADHDb	20	18.65 (±11.33)	395	11.29 (±12.12)	.008	.006
Other	94	12.65 (±12.08)	301	10.86 (±12.11)	.212	.187

^{a. Excluding those with ADHD                b. Excluding those with ASD      c. All other assessed diagnoses combined, exclusive of ASD and ADHD}                        

^{d. Adjusted for gender and neonatal head ultrasound abnormalities}

 

Conclusions:  In a non-referred preterm/LBW population, retrospectively assessed maternal childhood ADHD symptoms are associated selectively with offspring diagnoses of ASD and ADHD, suggesting that these diagnoses may have a common familial risk factor. This finding awaits replication in prospective follow-up studies of preterm/LBW infants as well as of term infants.