Abstract and Introduction
Suboptimal adherence to treatment regimens is a major obstacle to treatment efficacy and positive outcomes for patients. While poor adherence is common across a variety of chronic conditions, an area which presents unique challenges to clinicians and researchers is non-adherence among pediatric populations. These challenges are well illustrated by the management of attention-deficit/hyperactivity disorder (ADHD), a pervasive pediatric psychiatric condition. The average rates of non-adherence in children and adults ranged between 15 and 87%. Factors predicting increased adherence/persistence included the use of long-acting formulations, younger age, Caucasian background, family structure and the presence and treatment of comorbidities. Decreased adherence/persistence were predicted by multiple daily dosing, family history of ADHD, experiences of adverse effects, stigma and treatment inefficacy. The broad range of non-adherence rates identified reflects the complexities of adherence research in ADHD, and highlights the need for better standardization of adherence/persistence definitions and measurement approaches.
The multi-faceted dimensions of chronic health conditions are reflected in the complexity of their management practices, which stipulate the utilization of multiple treatment modalities and interventions, often over a prolonged period of time and across multiple settings. While this approach allows for more holistic management, it nevertheless presents several challenges to those affected. Perhaps the most apparent of these challenges is adherence, with figures from developed countries highlighting that only 50% of patients with chronic disease are adherent to their treatments.
As medication adherence has a central role in predicting morbidity and mortality associated with chronic illness, deviations from prescribed regimens can be expected to lead to a range of undesirable outcomes.[4–6] In the short term, non-adherence can affect treatment efficacy and tolerability while in the long term it can lead to poor therapeutic outcomes and increased economic disease burden.[7,8] Comparatively, adherence to treatment regimens has been associated with positive health outcomes, patient safety and improvements in quality of life[9–13] even when the treatment used is a placebo.[14,15] By extension, improving adherence can reduce medical expenditure and overall disease burden.
Non-adherence is considered to be a serious public health issue, presenting challenges not only to affected individuals, but to clinicians and policy makers alike. The gravity of this issue is heightened by the recognition that the prevalence of medication non-adherence is approaching 'crisis proportions'. This, coupled with the steady rise in the incidence of chronic conditions has catalyzed significant interest in investigating the underlying issues associated with non-adherence and developing ways to remedy this.
While extensive research has been conducted exploring these issues in a variety of conditions and populations, an area which poses unique challenges is medication adherence in pediatric populations.[18,19] Depending on the chronic condition in question, medication adherence rates among pediatric populations can be as low as 11%. What is of great interest in the pediatric setting is that the traditional patient–clinician dynamic is complicated as the parent becomes an intermediary between their child and the clinician. Children may have limited involvement in the treatment decisions made during consultations and can often be unaware of the purpose of prescribed treatments. In turn, medication adherence does not necessarily depend on the patient (child) alone, but also on the parent or caregiver who will often assume sole responsibility for administering the medication.[18,22] This parental involvement has the potential to introduce a number of factors which could influence adherence to treatment regimens. With regard to chronic illnesses in particular, parents often discontinue medications upon perceived resolution of symptoms, lack of effectiveness or observation of adverse effects.
These issues are particularly apparent in pediatric psychiatric disorders which often require pharmacological intervention well into adolescence and even adulthood.[23–26] Public resistance to biomedical conceptualizations for such disorders, and negative attitudes toward their treatment using medications may encourage premature termination of treatment. These issues are exemplified in attention-deficit/hyperactivity disorder (ADHD) which is a common chronic psychiatric disorder of childhood characterized by persistent and impairing symptoms of inattention, hyperactivity and impulsivity. The disorder is believed to affect between 5.9 and 7.1% of children and adolescents, with prevalence peaking during middle childhood and declining over time. The prevalence of ADHD among adults has been estimated to be approximately 2.5%. The experience of ADHD symptoms during adolescence and adulthood has been associated with impaired academic, occupational and social performance in addition to strained family relationships.[30,31]
Current ADHD treatment guidelines recommend a multi-faceted approach to treatment[32,33] incorporating the use of medications in conjunction with psychological and behavioral interventions where appropriate.[34,35] Stimulant medications such as methylphenidate (MPH) are considered first-line therapy for ADHD[36,37] as they have been shown to significantly improve symptoms[38–41] and are efficacious in approximately 80% of users. Due to the chronicity and nature of the impairing symptoms associated with ADHD, the use of such medications is often required over extended periods of time. Hence, adherence to these long-term medication regimens is important in the treatment of ADHD.[1,42,43]
Despite strong empirical evidence supporting their safety and efficacy,[44,45] adherence rates to stimulant medications for ADHD are poor and persistence rates of 15% 1 year after treatment initiation have been reported. These suboptimal figures are believed to be a major barrier to positive treatment outcomes. Poor medication adherence in ADHD not only leads to symptomatic relapse, but it can also affect clinicians' ability to determine treatment efficacy and to assess the need for dose or medication changes.[49,50] The severity of this predicament is emphasized by the understanding that ADHD is as prevalent as asthma in school-aged populations and accounts for greater annual healthcare expenditure. Hence, although this area hasn't traditionally been the focus of much interest, over the past 5 years there has been a surge in research examining the extent and causes of non-adherence to ADHD medications.
By reviewing the findings of recent research, this article aimed to explore the prevalence of non-adherence to ADHD medications and to provide insight into why users of ADHD medications cease treatment despite the persistence of symptoms and impairments. Users were defined as children, adolescents and adults with ADHD. The article begins with background information about the adherence measures used in the retrieved studies and is followed by the summarized findings of the literature search.
Expert Rev Pharmacoeconomics Outcomes Res. 2013;13(6):791-815. © 2013 Expert Reviews Ltd.