Individual differences and medication-mediation in chronic illness conditions: a mixed methods approach to the development of a novel, conceptual framework

Chronic illness is prevalent; adherence to pharmaceutical therapy facilitates an optimal outcome and is the single most influential affect in the individual’s illness trajectory. Hence, a prerequisite of efficacy is that medication is taken as prescribed. Adherence levels are, however, sub-optimal, with rates to pharmacological interventions as low as 17%; this represents a significant challenge to the effectiveness of therapy, undermining the benefits of clinical care. The reasons for nonadherence are various and complex, incorporating demographic factors, such as age and gender, cognitive variables including forgetfulness, as well as illness and treatment concerns, such as disagreeable symptoms and side effects. An underexplored factor, however, is the influence of personality factors on health behaviour, even though individual differences have been noted as central in health psychology. The ambit of this thesis is to explore the determinants of, and barriers to, pharmacological adherence in chronic illness, with a particular emphasis on personality affects; the overarching aims of the research are to develop a taxonomical framework of adherence factors and, further, a conceptual model demonstrating various influences of medication-taking. Two literature reviews were undertaken to establish what is currently known in extant literature; the first review, an expansive historical timeline, encompassed an appraisal of published literature in order to secure an overall understanding of topics that have been considered in relation to the phenomenon of medication adherence, and revealed the foci of adherence studies over the past few decades. This historical timeline evidenced that the biomedical stance is habitually used by researchers at the exclusion of patient’s perspectives, and highlighted a gaping lacuna in terms of individual differences; furthermore, the review formed a novel basis on which to contextualise the second systematic literature review and meta-analysis, which honed in on personality and its causal affects on medication adherence in chronic illness conditions. To substantiate quantitative data attained from the reviews and to expound the core dimensions underlying medication adherence, phenomenological investigation was performed. Emergent themes of experiential notions of adherence, informed by interviews with thirty-one participants, were thematically analysed; motifs included challenges with self-management in chronic illness, coping with an alteration in the self and notions of ‘normality’, together with psychosocial negotiation of the illness itself. Prior to interviews participants also completed psychometric assessments in order to ascertain adherence rates (the Medication Adherence Rating scale) and identify influential personality traits (the Five Factor Model). Data were synthesised to construct a comprehensive taxonomical framework of the diverse determinants of adherence, which deepens our understanding, facilitates an entry-point into adherence research and has significant utility as a research-informed theoretical structure. Additionally, the novel IndEx-MediC conceptual model of adherence was developed, predicated on findings that medication-taking is a mediational process influenced temporally, experientially, and contextually, determined by individual and external factors. The model presents a novel description of patients’ experiences of adherence to pharmaceutical therapy in chronic illness and serves as a foundation to develop a predictive measure to identify individuals potentially at risk of nonadherence, from which tailored interventional strategies may be devised.