Prescribing Trends of ADHD Medications in UK Primary Care

Date of ISAC Approval: 
Lay Summary: 
Millions of individuals worldwide are currently being treated for Attention-Deficit Hyperactivity Disorder (ADHD). ADHD is one of the most common mental disorders that develop in children, and partly continue in adolescents and adults. Over the last decades, a rapid increase in ADHD prescriptions has been observed in many countries including the UK that raised concerns about a possible over-diagnosis and inappropriate prescribing of ADHD drugs. In this context, the National Institute for Health and Care Excellence (NICE) issued a reminder in July 2013 to avoid methylphenidate in children and young people with moderate ADHD. However, impact of this recommendation has not been assessed. Moreover, there are no studies on the recent longitudinal trends of ADHD medications for children and adults in the UK. Therefore, the main objective of this study is to describe the secular trends in ADHD prescribing in UK primary care and evaluate time trends according to sex, age, and types of ADHD medications.
Technical Summary: 
This study aims to describe time trends of prescribing of ADHD medications over 1995-2015 for children and adults in the UK primary care. We will conduct a longitudinal study using data extracted from the United Kingdom's Clinical Practice Research Datalink (CPRD). Cohort will be defined as all patients between 6 and 45 years of age between 1 January 1995 and 30 September 2015. ADHD drugs will include methylphenidate, dexamphetamine (and lisdexamphetamine), and atomoxetine. The number of ADHD prescriptions will be calculated for each calendar year for each individual based on defined five age categories. Prescription rates will be estimated by dividing the total number of prescriptions in each calendar year by the total number of person-years at risk. We will calculate annual prescription rates and their corresponding 95% confidence intervals (CIs) using Poisson regression, and annual rates will be stratified by sex, age groups, and different ADHD drugs. Average annual change will be estimated by including calendar time as a linear predictor in the Poisson model.
Health Outcomes to be Measured: 
Prescribing of ADHD medications

Samy Suissa - Chief Investigator - McGill University
Christel Renoux - Collaborator - McGill University
Ju-Young Shin - Collaborator - McGill University
Sophie Dell'Aniello - Collaborator - McGill University