Factors influencing medication adherence in people with attention-deficit hyperactivity disorder and their parents/carers

Abstract

Introduction Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by inattention, hyperactivity, and/or impulsivity. ADHD can manifest itself as predominantly inattentive, predominantly hyperactive-impulsive, or a combination of both. Whilst the exact cause of ADHD is unknown, it is believed that the major contributing factors are genetics and environmental factors such as psychosocial adversity, pregnancy and birth complications, and exposure to toxins. ADHD is primarily a childhood disorder; however, it often persists into adolescence and adulthood. The worldwide prevalence of ADHD in children (under 18 years) is 7.1% (1). In adults, the mean prevalence of ADHD is 2.8% (2). In Australia, the prevalence of ADHD in children (aged 4-17 years) is 7.4% (3). In childhood, ADHD is more likely to impact the child’s cognitive abilities and school performances. In adolescence, ADHD casts doubts among adolescents about their own identity, and may promote anti-social behaviour and substance abuse. In adulthood, the person may have developed some degree of self-control; however, the symptoms remain problematic. Particularly, the ones associated with inattention and impulsivity, which may contribute to marital and employment-related issues. ADHD can be managed by pharmacotherapy, behavioural therapy (psychotherapy, educational therapy), or a combination of the two approaches. Numerous studies have demonstrated the effectiveness of medications in managing ADHD. Therefore, the use of medications is a common practice in clinical settings. Recent studies suggest that there has been a significant increase (as much as 100%) in the use of medication in the past decade (4). The long-term use of medication is critical to achieving the desired medication outcomes; however, studies have shown that adherence to ADHD medication is sub-optimal (9.8% to 64%) (5). Several factors have been reported in the literature that influence adherence to medication in people with ADHD; however, it is not clear how the factors impact adherence at its different phases (from initiation to discontinuation). Adherence to medication is a complex and dynamic process that changes over time during the medication-taking journey. The Ascertaining Barriers to Compliance (ABC) taxonomy has categorised this dynamic behaviour into three distinct but related phases: initiation, implementation, discontinuation. There is limited information in the literature about the impact of factors that influence adherence at the three phases in people taking medication for ADHD. Therefore, a comprehensive review of the literature was conducted to identify the factors that influence adherence at its three phases in people with ADHD. The review aimed to differentiate phase-specific factors. The factors were also differentiated based on different groups, such as children, adolescents, adults, and parents. As ADHD is primarily a childhood disorder, the involvement of parents was important as they are responsible for their child’s health and usually act as decision-makers about their child’s health including the use of medication. The review found considerable variability in how adherence was measured and the factors that influence adherence. More importantly, the review found some unique factors in each phase of adherence in addition to factors that were common across the phases. The review also found that factors can vary across different groups. The review concluded that it is important to examine adherence at each of the three phases because identification of phases-specific factors could help in better understanding the complex and dynamic nature of adherence, and to design targeted interventions to improve adherence. Furthermore, it was also important to quantify factors to determine the significance of their impact at the three phases of adherence. The literature review identified limited information about the relative importance of factors, and how people trade-off those factors to decide whether or not to adhere to medication. Aims and objectives The research project aimed to identify the factors that influence decision-making at the initiation, implementation and discontinuation phases of medication-taking in people with ADHD and parents of children with ADHD; evaluate the relative importance of those factors; and the extent to which patients and parents are willing to trade-off those factors to adhere to medication. The specific objectives of the research were:  To explore factors influencing initiation, implementation and discontinuation of medications in adolescents and adults with ADHD, and parents of children with ADHD.  To estimate the factors that influence parents’ and patients’ preferences to initiate and continue taking medication, the relative importance of those factors, and the extent to which patients and parents trade-off various medication attributes to initiate and continue medication.