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Abstract
Background
Although the worldwide prevalence of attention-deficit/hyperactivity disorder (ADHD) in adults is estimated to be between 2% and 5%, it is considered to be underdiagnosed. This register study explored the prevalence of diagnosed ADHD and incidence of newly diagnosed ADHD in Swedish adults over time, and assessed comorbidities and pharmacologic treatment.
Methods
National Patient Register data were used to estimate the overall prevalence of adults (≥18 years) with a registered ADHD diagnosis from 2006 to 2011, and the incidence of newly registered diagnoses from 2007 to 2011. Data from the Prescribed Drug Register were used to estimate the mean dose of the most frequently prescribed ADHD medication.
Results
The estimated annual prevalence (N=44,364) of diagnosed ADHD increased from 0.58 per 1,000 persons in 2006 to 3.54 per 1,000 persons in 2011. The estimated annual incidence of newly diagnosed ADHD (N=24,921) increased from 0.39 per 1,000 persons to 0.90 per 1,000 persons between 2007 and 2011. At least one comorbidity was diagnosed in 52.6% of adults with ADHD (54.0% of newly diagnosed adults), with anxiety, substance use disorders, and depression being the most common. Among all adults with ADHD, 78.9% (65.7% of newly diagnosed adults) were prescribed ADHD medication and one-third were prescribed more than one add-on medication. Osmotic release oral system methylphenidate was the most commonly used medication. The mean daily dose was 51.5 mg, and was significantly higher in males, patients with substance use disorders, patients with drug holidays, and patients with at least one add-on medication. The most frequent concomitant medications were anxiolytics and hypnotics.
Conclusion
In Sweden, the number of adults diagnosed with ADHD increased between 2006 and 2011, and the majority of patients were prescribed ADHD-specific medication. Over one-half of patients had psychiatric comorbidities; one-third were prescribed more than one add-on medication. Consumption of pharmacologic ADHD medication was high in specific patient subpopulations.
Acknowledgments
Under the direction of the authors, Jocelyn Woodcock, MPhil, of Caudex, Oxford, UK and Denise Graham, PhD, for Caudex, Oxford, UK, provided writing assistance for this publication, funded by Shire International GmbH. Editorial assistance in formatting, proofreading, copy editing, and fact checking the manuscript, and coordination and collation of comments, was provided by Caudex (funded by Shire International GmbH). This research was funded by Shire Sweden AB. Although employees of Shire were involved in the design, collection, analysis, interpretation, and fact checking of information, the content of this manuscript, interpretation of the data, and decision to submit the manuscript for publication in Neuropsychiatric Disease and Treatment was made by the authors independently.
Author contributions
YG, EA, and EM contributed to study design, manuscript development, and final manuscript review. MP contributed to data collection and analysis, manuscript development, and final manuscript review. All authors contributed toward data analysis, drafting and revising the paper and agree to be accountable for all aspects of the work. All authors approved the final version of the manuscript.
Disclosure
M Polyzoi is employed by PAREXEL International, which has been funded by Shire Sweden AB. E Ahnemark is employed by Shire Sweden AB. E Medin is employed by PAREXEL International, which has been funded by Shire Sweden AB. Y Ginsberg has over the past 3 years received speaker fees, reimbursement for travel costs, and/or served as a consultant for Novartis, HB Pharma, Shire, Eli Lilly, Hogrefe, Broadman Clarke Partners, Medscape, Medibas, and Natur & Kultur. The authors report no other conflicts of interest in this work.