There is still some debate over whether adulthood ADHD is simply childhood ADHD diagnosed later in life or whether it is a type of ADHD that has a late onset. With regards to treatment in individuals with ADHD, medication compliance in practice is still suboptimal. The aim of this study was to investigate and characterise medication compliance in adults with ADHD who were diagnosed in childhood compared with in adulthood using health insurance claims data.
This retrospective study included participants aged 18–23 years with claims related to ADHD and anti-ADHD medication from July 2017 to December 2018, and with a history of any International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) F90.0x* claims from January 2007 to June 2017 in the Korean National Health Insurance System (NHIS) Claims database. Participants were divided into those diagnosed with ADHD in childhood and those diagnosed in adulthood. Persistence, defined as the number of days of continuous therapy, and adherence, according to a medication possession ratio (MPR)† >80%, were calculated.
A total of 10,604 adults were included in the study; 8172 (77.06%) adults were assigned to the childhood ADHD group (mean [standard deviation (SD)] age of 19.65 [1.62] years) and 2432 (22.94%) adults to the adulthood ADHD group (mean [SD] age of 20.07 [1.79] years). In the childhood group compared with the adulthood group, there were more males (76.21% vs 54.61%, respectively), there was less use of National Health Insurance (91.89% vs 94.61%, respectively), and participants were more often treated by psychiatrists (96.56% vs 93.79%, respectively) and in hospitals (33.86% vs 25.90%, respectively; p<0.0001 for all comparisons). Combination therapy was the most common initial treatment in those with an adulthood diagnosis (45.81%), whilst methylphenidate was most common in those with a childhood diagnosis (47.48%).
The first 30-day gap in therapy occurred a mean (SD) time of 136.95 (124.91) days after treatment initiation in the adulthood group and 206.47 (126.74) days in the childhood group (p<0.0001). The proportions of medication persistence without a 30-day gap were 62.95% and 57.77% in the adulthood and childhood groups, respectively. An MPR of >80% was achieved in very similar proportions of the adulthood and childhood groups (63.3% and 63.8%, respectively). In the regression analysis excluding non-persistent participants, in both the adulthood and childhood groups, treatment in a private clinic (MPR >80%; odds ratio [OR] 1.602; 95% confidence interval [CI] 1.1–2.332 and OR 2.912; 95% CI 2.206–3.845, respectively; p<0.0001) and initiation with bupropion medication (OR 2.513; 95% CI 1.008–6.271 and OR 2.365; 95% CI 1.241–4.508) were significantly associated with adherence.
It was noted that the data used in this study were collected from the NHIS, a secondary database, therefore the effects of potentially significant factors such as educational level, socioeconomic status, intelligence, and disease severity or subtypes could not be determined. Furthermore, the results of this study were not generalisable for all adult age groups and were limited to only those in early adulthood. Finally, individuals with ADHD who did not use medical facilities covered by National Health Insurance could not be assessed in this study.
The authors concluded that significant differences were found between individuals who were diagnosed with ADHD in childhood versus adulthood, adding to the evidence which suggests that adults with ADHD diagnosed in adulthood may be treated separately from those in childhood. It was proposed that thorough evaluation at diagnosis and treatment in private clinics may improve medication compliance in this study population.
Read more about persistence and adherence in adults with ADHD here
*ADHD can be found in the ICD-10 under the code F90.0, Disturbance of Activity and Attention (Doernberg & Hollander, 2016)
†The MPR reflects the number of days for which patients were in possession of their prescribed medication. In this study, the MPR was calculated by summing the daily supply and dividing by the treatment period
Disclaimer: The views expressed here are the views of the author(s) and not those of Takeda.
Doernberg E, Hollander E. Neurodevelopmental disorders (ASD and ADHD): DSM-5, ICD-10, and ICD‑11. CNS Spectr 2016; 21: 295-299.
Lee SM, Cheong HK, Oh IH, et al. Comparison of persistence and adherence between adults diagnosed with attention deficit/hyperactivity disorder in childhood and adulthood. Neuropsychiatr Dis Treat 2021; 17: 3137-3146.