1. Introduction
In 2003, the World Health Organization (WHO) declared medication non-adherence as a worldwide issue of striking magnitude, which should be a priority for policymakers and health care providers [
1]. Despite this, medication adherence remains a global health concern [
2]. It is estimated that in developed countries, approximately 50% of adults with a chronic illness do not adhere to their medication regimens [
3], with this number expected to be even lower for preventative medications such as the oral contraceptive pill, which do not provide instant symptom relief [
4]. Poor medication adherence increases the likelihood of experiencing adverse medical events, worsening of condition symptoms, increased comorbidity, higher health care costs, and in some instances, higher risk of mortality [
5]. Similarly, medication non-adherence creates an economic burden, costing approximately USD 100–300 billion in the United States alone [
6]. With an increase in the number of co-morbid chronic diseases in adults, particularly young adults [
7], including diabetes, hypertension, mental health disorders, Crohn’s disease and arthritis [
8,
9,
10] it is important set up healthy and effective adherence patterns in young adulthood. The transition to adulthood is a difficult time for many, and a time where many begin to take control over their own health, however this population tends to be underrepresented in the adherence literature [
11,
12], with most research recruiting older adults.
There is a large body of scientific literature investigating medication adherence, or lack of adherence, using quantitative research methods. Many of these existing quantitative studies have employed the use of health psychology theories to explain non-adherence [
13], and to guide intervention creation in attempts to improve the behaviour [
14]. In attempting to understand medication adherence, these quantitative studies have identified the role of important mechanisms such as self-efficacy, perceived barriers, perceived susceptibility, necessity beliefs, and concerns about medication [
13]. Many of the theories have also been extended in attempts to negate weak relationships between variables (i.e., intention and behaviour in the theory of planned behaviour) [
15] or to explore the influence of non-psychosocial variables in medication adherence (i.e., side effects) [
16]. However, whilst these variables may be important for predicting adherence to various types of medications, it is not known which variables are more or less influential in predicting adherence to regimens of varying complexities. Complex medication regimens are commonly defined as taking at least five medications at one time [
17].
Temporal self-regulation theory (TST) [
18] is a newer theory of behaviour change that incorporates dual processes (e.g., rational and automatic processes) in the prediction of behaviour. The theory extends from the primary premise of the theory of planned behaviour which suggests that intention is the most proximal predictor of behaviour [
19] by incorporating additional processes, i.e., self-regulatory capacity (rational processes) and behavioural prepotency (automatic processes). Rational or conscious processes are those under volitional control, such as intention and some self-regulatory processes like planning, goal-setting and self-efficacy [
20]. Automatic or unconscious processes (i.e., habit) operate without conscious awareness and tend to be executed without thought [
21]. The theory proposes that intention, behavioural prepotency and self-regulatory capacity all directly predict behaviour. In addition, both behavioural prepotency and self-regulatory capacity are proposed to moderate the intention–behaviour relationship [
18].
Although temporal self-regulation theory has been quantitatively applied to various health behaviours [
22,
23,
24] it has only been applied to medication adherence in one study [
16]. In this study, the theory predicted approximately 50% of the variance in adherence to a range of medication types and regimen complexities, with both rational (intention, planning and self-control) and automatic (habit and cues) processes being important. However, this study did not individually investigate the predictors of adherence to simple or complex regimens. Certain variables in temporal self-regulation theory may be more important in simple regimens, rather than complex regimens, and vice versa. For instance, habit may be more predictive of adherence to a simple regimen, as taking a single medication at the same time every day is likely to become more habitual, and the repetition of a single action within the same context is an optimum environment for habits to form [
21]. Similarly, more complex medication regimens have been associated with decreased adherence [
25]. Thus, having a greater understanding of the modifiable predictors that may be associated with increased adherence to these complex regimens is important, not only for researchers tailoring interventions, but also general practitioners and pharmacists. One way to go about this is through the use of qualitative research methods, as quantitative explorations of behaviour change theories can only tell us what variables may be important in a behaviour but lack the “why”. Qualitative research also allows for the identification of additional variables that may not be accounted for in the theory, and may be capable at predicting additional variance when tested quantitatively. Furthermore, qualitative research is important in medication adherence research as it allows both researchers and clinicians to further understand medication adherence, or non-adherence, from the patient’s point of view, rather than just their responses to self-report measures, which may be biased [
26].
By focusing research on the modifiable psychological variables associated with adherence to different medication regimen complexities, interventions aimed at increasing adherence to various regimen complexities can be tailored. In addition, by having a further understanding of the influence of the variables that may not be modifiable or accounted for in behaviour change theories (e.g., side-effects), findings regarding these can be communicated with clinicians who can then provide their patients with ways of navigating and living with such effects, or be considered when designing interventions to improve adherence [
27].
The Current Study
To guide this qualitative research study, the overarching research questions “what variables from temporal self-regulation theory are important in adhering to different medication regimens, specifically simple and more complex regimens?” and “are there any additional variables, not included in the theory, that are important in effectively adhering to these different regimens?” were explored. The overarching aim was to explore how temporal self-regulation can help explain medication adherence in people’s daily lives, and whether the theory explains different patterns of behaviour in the adherence to simple and complex medication regimens. An inductive and deductive qualitative approach was used to ensure the possibility of identifying other additional variables that are important in adherence, and that are not accounted for in the theory. As temporal self-regulation theory only accounts for a moderate amount of variance, the identification of additional influences is just as important.
5. Conclusions
The present study sought to explore the utility of temporal self-regulation theory in helping to explain medication adherence in people’s daily lives, specifically in how they adhere to their medication regimens, and whether there are any differences in how the theory operated in adherence to different medication regimen complexities. Six themes that influence adherence were identified. Differences between regimen complexities appeared, such that participants who take between three and five medications spoke more on the importance of having a consistent routine, planning and seeking knowledge. Participants taking only one medication highlighted the importance of implementing cues, specifically visual, to assist in adherence. The findings show some support for temporal self-regulation theory, specifically intention, past behaviour, cues and planning, but many non-psychological influences were also identified, such as the cheap cost of medications, support from health professionals and friends, the experience of side-effects, avoiding negative symptoms of the condition and being involved in the process. However, complex regimens were not necessarily captured in the university sample and therefore future research should consider applying the theory to samples with distinct simple and complex regimens. Future research may also consider investigating the role of visual or contextual cues in simple regimens to see if adherence can be improved over time.