Elsevier

Social Science & Medicine

Volume 68, Issue 6, March 2009, Pages 1060-1068
Social Science & Medicine

The effects of trust in physician on self-efficacy, adherence and diabetes outcomes

https://doi.org/10.1016/j.socscimed.2008.12.033Get rights and content

Abstract

Trust in physicians has been associated with a range of patient behaviors. However, previous research has not focused on the mechanisms by which trust affects health outcomes and mostly has made use of self-rated health. This study tested a theoretical model of variables influencing the relations of trust to both objective and self-rated health. We hypothesized that patients who trust their physicians more were likely to have stronger self-efficacy and outcome expectations. We expected this, in turn, to be associated with better treatment adherence and objective health outcomes. In addition, we hypothesized that highly trusting patients would be more likely to report better health status through enhanced self-efficacy. Data for this research came from a sample of 480 adult patients with type 2 diabetes in Taiwan. Patients completed measures of trust, self-efficacy, outcome expectations, adherence, and the SF-12 health survey. Objective outcomes, including body mass index, glycosylated hemoglobin, blood lipid, and diabetes-related complications, were assessed by follow-up chart review. The structural equation analyses which were implemented by LISREL VIII resulted in a proper solution that exhibited adequate fit. All hypothesized paths were statistically significant and in the predicted directions. The mediation roles of self-efficacy and outcome expectations were further confirmed by the results of structural equation modeling and bootstrap analyses. In the multivariate regression, although the relations of patient trust to blood lipid and self-rated health were confirmed, the direct link of trust to glycosylated hemoglobin was only significant in the bivariate model. This study clarifies the association of trust with different types of health outcomes and provides the empirical evidence that trust in physicians is associated with both self-rated health and therapeutic response. However, a more longitudinal study design is necessary to precisely determine both the strength and causality of these relationships.

Introduction

Trust in the physician is a patient's optimistic acceptance of a vulnerable situation, based on the expectation that the physician will act in the patient's best interest (Hall, 2006). Although trust is important in health organizations as shown by the increasing amount of research and theory on the topic, little is known about how trust relates, and through what mechanisms, to measurable health outcomes (Hall, 2006, Pearson and Raeke, 2000). The value of trust in health care contexts derives in large part from its potential to improve the efficacy of treating disease. Therefore, research on trust will be incomplete if we fail to tackle questions about relationships between trust and health care outcomes.

The present study seeks to extend existing research on trust in two ways. First, much of the past research has relied mainly on self-rated measures of outcomes, such as current general health status (Kao, Green, Zaslavsky, Koplan, & Cleary, 1998), or reported improvement of symptoms (Thom, Kravitz, Bell, Krupat, & Azari, 2002). Concerned about the limitations of these data, some researchers have urged using objective, independently observed outcome measures to examine health outcomes (Hall, Dugan, Zheng, & Mishra, 2001). Our study assesses the effect of trust on health outcomes by drawing on laboratory data from patients' medical records. In addition, we adopted a more sophisticated 12-Item Short-Form Health Survey (SF-12) instead of the single-item measures used in other studies concerning similar topics (Armstrong et al., 2006, Mohseni and Lindstrom, 2007, Thom et al., 2002)

Second, while some studies have researched outcomes of patient trust, detailed conceptual analyses and empirical information are scarce as to how trust actually contributes to health outcomes. It has been suggested that trust can improve therapeutic response through better treatment adherence (Thom, Hall, & Pawlson, 2004). The empirical basis to move beyond this speculation is limited. Similarly, past research has not addressed the issue of why patient trust would be related to adherence. Based on the self-efficacy theory (Bandura, 1986), we proposed both self-efficacy and outcome expectations as possible mediators that might link trust with patient adherence.

We posed two questions in the present research: Is patients' trust in physicians associated with better health outcomes? How and why would such associations occur? Fig. 1 illustrates our proposed relations and provides an overview of the study.

Capturing the key elements of the concept as highlighted by various disciplinary lenses, Bhattacharya and Devinney (1998) define trust as “the expectancy of positive outcomes that one can receive with the action of another party in an interaction characterized by uncertainty.” Recent public health surveys have found that low trust in the health care system is associated with poor self-rated health (Armstrong et al., 2006, Mohseni and Lindstrom, 2007). Likewise, research has reported that trust in one's physician is positively correlated with self-reported health status (Kao et al., 1998), symptom improvement (Thom et al., 2002), and physical and mental health-related quality of life (Préau et al., 2004). As trust has long been recognized as an important precursor of cooperation, a patient's intention to accept vulnerability is based on the level of trust. Without trust, cooperative behaviors--such as following physician's recommendations--are hard to achieve (Dibben, Morris, & Lean, 2000). Consequently, patient's health outcomes, as a result of effective care and increased adherence, are more likely to be improved.

Kaplan, Greenfield, and Ware (1989) have shown a significant relation between patient–physician relationships and both functional and mental health outcomes. Since trust is the core component of therapeutic partnerships in health care, we expected patients with higher levels of trust to have better health outcomes than patients with lower levels of trust. Accordingly, we hypothesized:

Hypothesis 1

Patient's trust in the physician is positively associated with self-rated health (Hypothesis 1a) and objective health indicators (Hypothesis 1b).

Although researchers have examined the relation between trust, self-efficacy, and outcome expectations in non-health care settings (Ergeneli, Arı, & Metin, 2007), a look at the health care literature reveals a lack of research in this area. However, Crow et al. (1999) have proposed the patient–physician relationship as a critical determinant of these two types of expectations. Consequently we tested a model that examined self-efficacy and outcome expectations as mediators of the link between trust and patient adherence, and adherence as a mediator between trust and health outcomes.

The explanation for trust and cooperative behavior in previous research hinges on the positive expectations engendered by trust (Bhattacharya and Devinney, 1998, Gambetta, 1988). When patients feel their physicians are trustworthy, they expect better results from the physicians' recommended health behaviors or treatment plans. However, effort and performance are a function of not only the outcomes individuals expect will result from their action but also their efficacy expectations (Bandura, 1986). Although some studies have proposed that patient–physician relationships are a key determinant of self-efficacy (Ohya et al., 2001, Zachariae et al., 2003), research to date has not evaluated the relation between trust and patients' self-efficacy.

Self-efficacy, defined as confidence in one's ability to perform a specific behavior or set of behaviors (Bandura, 1977), reflects context-specific evaluations of one's capabilities to mobilize motivation, cognitive resources and courses of action. In this study, the term self-efficacy refers to the patient's belief in his/her ability to carry out specific self-care behaviors. How trust influences a patient's self-efficacy regarding adherence may operate through a number of means (Bandura, 1997). First, because mastery of experience is the most influential source of efficacy information (Bandura, 1986), patients' sense of efficacy is likely to be shaped by previous successes in trusting settings. Second, through support and realistic encouragement, a trusted physician's persuasion can enhance patients' efficacy and motivate them to overcome the impediments to adherence. Third, higher levels of anxiety serve as negative feedback that can erode self-efficacy (Bandura, 1997). However, patients are likely to feel less anxious if a trusted physician is making treatment decisions (Hall et al., 2001) resulting in higher self-efficacy.

Based on this research, we expected that trusting patients would have higher levels not only of outcome expectations but also of self-efficacy. We also expected that self-efficacy and outcome expectation would mediate the trust–adherence link. In general, self-efficacy and outcome expectations are highly correlated with patient adherence to treatment (Iannotti et al., 2006). For example, a study of motivation to exercise in stroke survivors found that self-efficacy and outcome expectations were key determinants of adherence to both initiating and maintaining exercise programs (Shaughnessy, Resnick, & Macko, 2006). Rosenbaum (1990) posited that the patient–physician relationship may influence the process-regulating cognition that underlies adherence to treatment. Taken together, we advanced the hypothesis as follows:

Hypothesis 2

Self-efficacy and outcome expectations mediate the relationships between trust in the physician and patient adherence.

Medical studies have shown that adherence is a primary determinant of treatment effectiveness and health outcomes (Kuo et al., 2003). Because improved treatment adherence may close the gap between potential and actual treatment benefits, the full benefit of a prescribed medication is achieved only if a patient follows the treatment recommendations reasonably closely. Thus,

Hypothesis 3

Patient adherence is positively associated with patient's objective health outcomes.

Evidence from meta-analyses across diverse spheres of functioning consistently shows that efficacy contributes significantly to performance including health outcomes (Bandura & Locke, 2003). In relation to health, individuals with strong self-efficacy have less feeling of helplessness and faster recovery from difficulty (Smarr et al., 1997). Compared to people with a low efficacy, patients with a high efficacy are also less likely to perceive themselves as sick or depressed (Bandura, 1997). Empirically, chronic illness research has shown that self-efficacy significantly predicts a sense of physical and emotional well-being (Hochhausen et al., 2007, Joekes et al., 2007).

Collectively, patients with a high level of trust are more likely than other patients to believe that they can overcome difficulties and favorably influence outcomes (high self-efficacy expectations). When patients' self-efficacy is strengthened, they are more resilient, adjust better to the sick role, and report better health status. Accordingly, we hypothesized:

Hypothesis 4

Patient's self-efficacy mediates the relations between trust in the physician and patient's self-rated health.

Section snippets

Research site and participants

We examined cross-sectional and follow-up data from a sample of adult patients with type 2 diabetes from one medical center, one regional hospital and one district hospital in Taiwan. Three facilities were chosen to involve a range of patients from different social, economic and ethnic backgrounds, which allowed a relatively realistic picture of patients who are undergoing routine treatment in various outpatient facilities. The study was approved by the Local Institutional Review Board, and

Results

The regression results of trust on outcomes are shown in Table 2. As expected, trust had a positive association with self-rated physical (ΔR2 = .01, β = .11) and mental (ΔR2 = .06, β = .24) HRQoL. Thus, Hypothesis 1a was supported. In relation to objective outcomes, trust had a positive association with triglycerides (ΔR2 = .01, β = −.09) but minimal association with body mass index and complications. Although trust was associated with glycosylated hemoglobin in the bivariate model, the association was not

Discussion

Our study makes two key contributions to the literature on patient trust, showing both how and why trust is linked to patients' health. The structural equation analysis confirmed the study's overall hypothesized model. Patients who trusted their physicians were significantly more likely to have stronger self-efficacy and outcome expectations, which in turn were associated with better treatment adherence and clinical outcomes. Also, highly trusting patients were likely to report better health

Conclusion

Our study provides empirical evidence that trust in physicians is associated with both self-rated and objective health outcomes. As health care organizations continue to devote vast resources to quality of care improvement, the need for a better understanding of effective health care relationships continues to grow. We have sought to develop a framework for understanding trust as a potential contributor to the outcomes of health care, deriving implications for the roles of health care providers

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    We would like to thank TK Peng for his input in the design of this study. We are also grateful to the helpful comments of the editor and anonymous reviewers in revising our paper.

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