Background:
Attention Deficit Hyperactivity Disorder (ADHD) is a common neurodevelopmental disordercharacterised by the symptoms of inattention, impulsivity and hyperactivity. ADHD was onceperceived as a condition of childhood only; however increasing evidence has highlighted theexistence of ADHD in older adolescents and adults. Estimates for the prevalence of ADHD inadults range from 2.5-4%. Few data exist on the prescribing trends of the stimulantsmethylphenidate and dexamfetamine, and the non-stimulant atomoxetine in the UK. The aimof this study was to investigate the annual prevalence and incidence of pharmacologicallytreated ADHD in children, adolescents and adults in UK primary care.
Methods:
The Health Improvement Network (THIN) database was used to identify all patients agedover 6 years with a diagnosis of ADHD/Hyperkinetic Disorder (HKD) and a prescription formethylphenidate, dexamfetamine or atomoxetine from 2003-2008. Annual prevalence andincidence of pharmacologically treated ADHD were calculated by age category and sex.
Results:
The source population comprised of 3,529,615 patients (48.9% male). A total of 118,929prescriptions were recorded for the 4,530 patients in the pharmacologically treated ADHDcohort during the 6-year study. Prevalence (per 1000 persons in the mid-year THINpopulation) increased within each age category from 2003 to 2008 [6-12 years: from 4.8(95% CI: 4.5-5.1) to 9.2 (95% CI: 8.8-9.6); 13-17 years: from 3.6 (95% CI: 3.3-3.9) to 7.4(95% CI: 7.0-7.8); 18-24 years: from 0.3 (95% CI: 0.2-0.3) to 1.1 (95% CI: 1.0-1.3); 25-45years: from 0.02 (95% CI: 0.01-0.03) to 0.08 (95% CI: 0.06-0.10); >45 years: from 0.01(95% CI: 0.00-0.01) to 0.02 (95% CI: 0.01-0.03). Whilst male patients aged 6-12 years hadthe highest prevalence; the relative increase in prescribing was higher amongst femalepatients of the same age – the increase in prevalence in females aged 6-12 years was 2.1 foldcompared to an increase of 1.9 fold for their male counterparts. Prevalence of treated ADHDdecreased with increasing age. Incidence (per 1000 persons at risk in the mid-year THINpopulation) was highest for children aged 6-12 years.
Conclusions:
A trend of increasing prescribing prevalence of ADHD drug treatment was observed over theperiod 2003-2008. Prevalence of prescribing to adult patients increased; however thenumbers treated are much lower than published estimates of the prevalence of ADHD. Thisstudy has added to the limited knowledge on ADHD prescribing in primary care, particularlyin the area of drug treatment in adulthood.