Causal modelling of variation in clinical practice and long-term outcomes of ADHD using Norwegian registry data: the ADHD controversy project

Arnstein Mykletun, Tarjei Widding-Havneraas, Ashmita Chaulagain, Ingvild Lyhmann, Ingvar Bjelland, Anne Halmøy, Felix Elwert, Peter Butterworth, Simen Markussen, Henrik Daae Zachrisson, Knut Rypdal, Arnstein Mykletun, Tarjei Widding-Havneraas, Ashmita Chaulagain, Ingvild Lyhmann, Ingvar Bjelland, Anne Halmøy, Felix Elwert, Peter Butterworth, Simen Markussen, Henrik Daae Zachrisson, Knut Rypdal

Abstract

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is among the most common mental disorders in children and adolescents, and it is a strong risk factor for several adverse psychosocial outcomes over the lifespan. There are large between-country and within-country variations in diagnosis and medication rates. Due to ethical and practical considerations, a few studies have examined the effects of receiving a diagnosis, and there is a lack of research on effects of medication on long-term outcomes.Our project has four aims organised in four work packages: (WP1) To examine the prognosis of ADHD (with and without medication) compared with patients with other psychiatric diagnoses, patients in contact with public sector child and adolescent psychiatric outpatient clinics (without diagnosis) and the general population; (WP2) Examine within-country variation in ADHD diagnoses and medication rates by clinics' catchment area; and(WP3) Identify causal effects of being diagnosed with ADHD and (WP4) ADHD medication on long-term outcomes.

Method and analysis: Our project links several nationwide Norwegian registries. The patient sample is all persons aged 5-18 years that were in contact with public sector child and adolescent psychiatric outpatient clinics in 2009-2011. Our comparative analysis of prognosis will be based on survival analysis and mixed-effects models. Our analysis of variation will apply mixed-effects models and generalised linear models. We have two identification strategies for the effect of being diagnosed with ADHD and of receiving medication on long-term outcomes. Both strategies rely on using preference-based instrumental variables, which in our project are based on provider preferences for ADHD diagnosis and medication.

Ethics and dissemination: The project is approved by the Regional Ethics Committee, Norway (REC number 2017/2150/REC south-east D). All papers will be published in open-access journals and results will be presented in national and international conferences.

Trial registration numbers: ISRCTN11573246 and ISRCTN11891971.

Keywords: child & adolescent psychiatry; epidemiology; mental health.

Conflict of interest statement

Competing interests: None declared.

© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.

Figures

Figure 1
Figure 1
Theoretical model on clinicians’ consensus on diagnosis and medication by ADHD symptom load among referred patient. ADHD, attention-deficit/hyperactivity disorder.
Figure 2
Figure 2
Two sources of as-if randomisation. Quasi-experiment 1 is provider preference for ADHD diagnosis. Quasi-experiment 2 is provider preference for ADHD medication among those diagnosed with ADHD. ADHD, attention-deficit/hyperactivity disorder.
Figure 3
Figure 3
County variation in ADHD diagnosis and medication percent for children and adolescents between 10 and 19 years in Norway. ADHD as main diagnosis registered once or more times during 2009–2011. Registered diagnosis in NPR 2009–2011 and registered filled ADHD prescription NorPD 2012. ADHD, attention-deficit/hyperactivity disorder; NorPD, Norwegian Prescription Database; NPR, Norwegian Patient Register; WP, work package.
Figure 4
Figure 4
Scatterplot of ADHD diagnosis and medication among children and adolescents between 10 and 19 years by Norwegian counties. ADHD as main diagnosis registered once or more times during 2009–2011. Linear fitted line. Registered diagnosis in NPR 2009–2011 and registered filled ADHD prescription NorPD 2012. ADHD, attention-deficit/hyperactivity disorder; NorPD, Norwegian Prescription Database; NPR, Norwegian Patient Register.

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