Rachael Morkem, Scott Patten, John Queenan, and David Barber

Journal of Attention Disorders 1 –8 , 2017 DOI: 10.1177/1087054717720719

This study describes trends the incidence and prevalence of prescribing ADHD medication in a large Canadian Primary Care Physician (PCP) Network over a ten year period from 2005-2015. Canada has public funded health care, creating a system that the provision for chronic disorders (such as ADHD) is often provided by PCPs, who serve as gatekeepers to specialty referrals only when necessary. A population-based retrospective cohort was derived from EMR data from the Canadian Primary Care Sentinel Surveillance Network, which has 11 practice-based research networks (PBRNs) composed of 1,100 primary care practitioners throughout Canada. Total number of prescriptions, type of medication, age group were assessed by year throughout the ten-year span. The annual prevalence was determined by establishing the number of patients prescribed at least one ADHD medication, divided by total number of patients with a PCP visit that year. Annual incidence rates were established using a similar formula for patients who were receiving their initial treatment with ADHD medication. The authors found over the decade a 2.5 and 2.6 fold increase in the prescribing prevalence in preschool and school age children, respectively and a 4 fold increase in prescribing prevalence in adults. Methylphenidate was the most commonly prescribed medication over the decade (65%), with a slight decrease in the later years of the decade, presumably due to the introduction of the long-acting amphetamine lisdexamphetamine. The authors noted that although ADHD disease prevalence was stable, the prescribing prevalence was increasing over the decade. Also gender differences of higher prescribing rates of boys:girls in children and adolescents were not seen in adults. The investigators posit that since the ADHD disease prevalence was noted to be relatively stable in Canada (Hauck et al. 2017), and the frequency of medication prescription remains below ADHD prevalence, the increased prevalence of prescriptions may reflect improved long-term treatment. Several caveats should be noted to this study: 1) the most common annual frequencies of taking medications were in the 20% range for once or >=10/year; this bimodal distribution may indicate ongoing issues with adherence to medications in Canadanian ADHD patients, 2) the authors were unclear as to how they handled patients who switched between medication preparations and 3) as the authors note, the study is only able to examine what was prescribed, but not what was taken. One take home point for US clinicians is the higher utilization of methylphenidate products in the Canadian population as compared to what has been described in US adult ADHD populations.

REFERENCES:
Hauck, T. S., Lau, C., Wing, L. L. F., Kurdyak, P., & Tu, K. (2017). ADHD treatment in primary care: Demographic factors, medication trends, and treatment predictors. Canadian Journal of Psychiatry, 62, 393-402.