Antipsychotic Drug Prescribing in Children Previously Treated With Stimulants for ADHD: A Population-Based Longitudinal Study: La prescription d'antipsychotiques chez les enfants précédemment traités avec des stimulants pour le TDAH : une étude longitudinale basée sur la population

Objective Stimulant drug treatment in preschool-age children for attention-deficit hyperactivity disorder (ADHD) as well as the concomitant use of antipsychotic drugs is largely unstudied in terms of longitudinal outcomes. We characterized longitudinal patterns of stimulant drug use in children diagnosed for ADHD and analyzed the mental health disorders leading to add-on therapy with antipsychotics.Method The study population comprised of children and adolescents (age: 0-19 years) in the province of British Columbia (BC), Canada, with at least one dispensing for any psychotropic drug between 1997 and 2017 (N = 144,825). BC health administrative databases were used to identify children with diagnosis for ADHD and dispensings for stimulant and antipsychotic drugs. Longitudinal patterns of drug use and diagnostic codes proximal to the add-on of antipsychotics were assessed.Results We found that residence in rural regions and lack of child psychiatrists are significantly associated with higher rates of stimulant drug prescription in preschool and early school-age children. Residence in rural regions was also associated with a higher rate for the concomitant use of antipsychotics over the course of stimulant treatment. When comparing children starting stimulant therapy before the age of 6 with those starting therapy after 6 years, we found an 82% increase in the likelihood of antipsychotic add-on in those starting stimulants at younger ages (HR: 1.82, 95% CI [1.63-2.04]). Moreover, children starting stimulant therapy before the age of 6 years had 3.57-fold higher rates of diagnostic codes for specific delays in development (ICD-9 315) in close proximity to the antipsychotic add-on.Conclusions The question remains whether the add-on of antipsychotics is a consequence of insufficient action of the stimulant in ADHD, or required to ameliorate the adverse effects of the stimulant drug. Our result suggests that care need to be taken in the diagnosis for ADHD in children at the age when entering elementary school.