(193) Stimulant Drug Use in Children Before Six Years of Age and Antipsychotic Add-on Therapy: A Population Based Longitudinal Study

Publication Number: 1238

Background: Stimulant drugs, such as methylphenidate and amphetamine, are frequently prescribed to children at early school age for treatment of attention-deficit hyperactivity disorder (ADHD). Stimulant drugs enhance dopaminergic neurotransmission, a major contributing factor in the development of psychosis.

Objectives: To characterize the pattern of stimulant use in children and adolescents up to the age of 19 years and determine their requirement for antipsychotic drugs in relation to frequency, age at onset (index date), and local health area (i.e., urban v. rural) of stimulant use.

Methods: Longitudinal patterns of stimulant- and antipsychotic drug use in children were analyzed using British Columbia health administrative databases (PharmaNet, Medical Services Plan, Vital Statistics) from 1997 to 2018. Children having been on stimulants for at least one year and with ADHD diagnosis were identified; those received antipsychotics before index date (first stimulant prescription) were excluded. We conducted Kaplan Meier estimates of the rates of antipsychotic add-on following the index date. To quantify factors associated with antipsychotic add-on, the cohort was stratified by their frequency of stimulant use, age at first prescription of stimulants, and by their local health area. Cox regression was fitted for both unadjusted and adjusted models. Hazard ratios and 95% CI were presented for each included covariate.

Results: We found 14,924 patients that met the inclusion criterion in this cohort study. The mean age of starting stimulants is 9.9 years (sd=3.8), Males were significantly younger. While stimulant use remains low under the age of 5 years, we find a sudden increase before the age of 6 years, at the period when children enter elementary school. After using stimulants, the average time up to antipsychotic add-on is 5.9 years (sd=4.5). Most important, in the adjusted Cox regression model, patients who started stimulants close to school age, were 88% more likely to have antipsychotic add-on than those started above 6 years of age.

Conclusions: Children starting stimulant use < 6 years of age are more than 8x more likely to require an antipsychotic medication within a period of 7 years from the index date. Rural areas have more antipsychotic add-on, likely due to fewer mental health services available for children in those communities.
Study limitations are the absence of a cohort with diagnosis of ADHD but untreated with stimulant drugs.