Do Externalizing and Internalizing Symptoms Moderate Medication Response in Preschool Attention-Deficit/Hyperactivity Disorder? A DBPNet Study.

OBJECTIVES: This study aimed to determine whether parent ratings of attention-deficit/hyperactivity disorder (ADHD) symptom severity or externalizing symptoms (EXT) or internalizing symptoms (INT) moderate response to stimulants (STIM) and alpha-2 adrenergic agonists (A2As) in preschool ADHD.

METHODS: Health records for children treated with medication for ADHD and with parent rating scale data available (N = 309; age <72 months) were reviewed at 7 Developmental-Behavioral Pediatric Research Network sites. Severity of ADHD was defined as the number of ADHD symptoms occurring often or very often on DSM-IV-based parent rating scales. EXT or INT from standardized rating scales were categorized as T score <60, 60 to <70, or ≥70. Ordinal logistic regression models predicting response to medication were calculated.

RESULTS: The median (interquartile range) age at ADHD diagnosis was 59 (54-65) months. One hundred eighty-three participants had ADHD symptom severity, and 195 had EXT or INT data. ADHD severity was not associated with medication response. Both EXT and INT were associated with medication response but with significant medication class by EXT/INT interactions. Children with higher EXT were less likely to respond to STIM, with percentage of nonresponders for T-score categories <60, 60 to <70, and ≥70 being 3.6%, 25.7%, and 33.3% (p = 0.016) and, for A2As, being 60%, 50%, and 33.3% (p = 0.55), respectively. A similar pattern was observed for INT categories: STIM 19.4%, 22.5%, and 50.0% (p = 0.002) and A2As 42.3%, 30%, and 42.3% (p = 0.48), respectively.

CONCLUSION: For preschool ADHD, low ratings of EXT or INT are associated with a high likelihood of response to STIM. By contrast, response rates to STIM and A2As are more similar for children with high levels of EXT or INT.