Motivational Interviewing: An Evidence-Based Approach for Use in Medical Practice
Background: Motivational factors in health-relevant modes of behavior are an important matter in medical practice. Motivational interviewing (MI) is a technique that has been specifically developed to help motivate ambivalent patients to change their behavior.
Methods: This review is based on pertinent publications retrieved by a selective search in the PubMed, Cochrane, and Web of Science databases. Special attention was paid to systematic reviews and meta-analyses concerning the efficacy of MI in the medical care of various target groups. The present review focuses on the relevance of MI for patients with highly prevalent disorders.
Results: Meta-analyses reveal statistically significant mean intervention effects of MI in medical care with respect to a variety of health-relevant modes of behavior, in comparison to standard treatment and no treatment in the control groups (odds ratio [OR]: 1.55; 95% confidence interval: [1.40; 1.71]). Statistically significant effect sizes were reported for substance consumption, physical activity, dental hygiene, body weight, treatment adherence, willingness to change behavior, and mortality; effects on health-promoting behavior were mixed. Studies of the factors that contribute to the efficacy of MI suggest that it exerts its effects largely through the selective reinforcement of statements made by the patients themselves about potential changes in their behavior.
Conclusion: MI has been found useful for strengthening the motivation for behavioral change in patients with various behaviorally influenced health problems and for promoting treatment adherence. It can be used to optimize medical interventions. Further research is needed with respect to its specific mechanisms of action, its efficacy in reinforcing health-promoting modes of behavior, differential indications for different patient groups, and the cost-efficiency of the technique across the spectrum of disorders in which it is used.
In highly developed industrialized countries, behavioral risk factors such as substance use (tobacco, alcohol), unhealthy diet, and insufficient physical activity are a key determinant of the burden of disease in the population as measured by disability-adjusted life years (DALYs) (1). These factors also have a crucial impact on the course of a variety of chronic diseases.
For example, according to the Global Burden of Disease study, the 23.9 million DALYs lost in the German population in 2010 can be attributed in percentage terms to the following causes (2):
- Unhealthy diet (men: 16.2%, women: 11.2%)
- Smoking (men: 14.2%, women: 6.7%)
- High blood pressure (men: 11.5%, women: 10.2%)
- Overweight (men: 11.5%, women: 10.3%).
Therefore, motivational aspects are a significant factor in patient treatment. Other important motivational factors for medical practice stem from the often insufficient adherence to medication, which, according to a number of studies, lies between 31.2% and 59.1% and also represents a significant factor in the chronification of health impairments (3, 4, 5).
Furthermore, societal changes in recent decades that challenge our understanding of the clinician’s role are reflected in the concept of “shared decision-making,” according to which treatment steps should be developed in consultation with the patient (6).
Motivational interviewing (MI) (7), which originated in the field of addiction treatment, is a promising concept for encouraging motivation to change in patients that are currently either unwilling or ambivalent to change, and can be deployed even with limited time resources. Since the first publications on the approach in the early 1980s, it has also been increasingly used, and successfully so, in other disciplines. This article presents the basic principles of the approach from the perspective of their applicability in medical practice. To assess the effectiveness of the method, systematic reviews and meta-analyses published in the PubMed, Cochrane, and Web of Science databases since 2005 on the effectiveness of MI across disorders in medical treatment settings, as well as on the effectiveness of MI on medication adherence, were selectively searched and summarized using the search terms (“Motivational Interviewing” AND (“primary care” OR “medical care”).
Basic tenets of motivational interviewing
Although MI is not a theory-guided approach, it nevertheless combines a variety of evidence-based approaches from cognitive psychology and social psychology. MI assumes that people with problematic behaviors (for example, smoking, high-risk alcohol consumption, unhealthy diet, lack of medication adherence, insufficient exercise) have different levels of readiness for behavior change.
According to Janis and Mann’s conflict-theory model of decision-making (8), the advantages of healthy behaviors (such as better health prognosis and improved fitness, among others) are always countered by disadvantages of behavior change (for example, loss of hedonistic reinforcers, significant effort, possible side effects of medication). The assumption in MI is that people with problematic behaviors are not fundamentally unmotivated to change their behavior, but are instead ambivalent, that is to say, their problem behavior conflicts at least to some extent with their self-concepts, values, or life goals, with those affected potentially having subjectively good reasons against a behavior change. If this ambivalence is not recognized, well-intentioned medical advice is perceived by patients as an assault on their freedom of choice, which, according to socio-psychological reactance theory (9), increases their motivation to restore their own subjective power to make decisions. This, in turn, often results in non-compliance either in the form of open disagreement or non-adherence to recommendations. A prerequisite of sustained encouragement of motivation to change is that patients become more aware of their behavioral discrepancies and actively confront their behavior. Therefore, MI is defined as “a person-centered, goal-oriented style of communication with particular focus on expressions of change. The goal is to increase personal motivation for and commitment to behavior change by eliciting and intensifying a person’s own reasons for change in an atmosphere of acceptance and empathy” (7). In line with self-determination theory (SDT; ), the approach recognizes the needs for autonomy, competence, and relatedness. As such, the atmosphere of acceptance and empathy represents a necessary condition for patients’ self-disclosure in interviews relating to difficult or stigmatized subjects such as substance use, overeating, or health problems. The authors of MI have repeatedly emphasized that MI is not a technique, but a fundamental therapeutic style that does not seek to make people change their behavior against their will. Roger’s person-centered therapy (11) forms an important basis of the approach, whereby MI is characterized by a goal-oriented approach and can essentially be combined with other therapeutic methods. The hallmark of MI is a differentiation into inner attitude (“human image”), methods and principles of implementation, as well as different processes of implementation (Box 1).
Techniques of motivational interviewing
In addition to the basic principles of MI, the method includes altogether five intervention techniques, the importance of each of which may vary depending on the patient and the status of their treatment (7). The first four intervention techniques are methods that are also used in other schools of therapy, such as client-centered interviewing.
First intervention element
Open-ended questions are helpful for encouraging patients to confront their problem behavior, for example, “What worries you about your drinking?” MI is deemed to be good when at least 70% of the questions asked are open-ended (12).
Second intervention element
Active listening makes it possible to discover and focus on the patient’s concerns regarding their problem behavior. As part of this process, the clinician reflects back to the patient the essential content of their statements. Furthermore, active listening not only has the effect that the individual experiences understanding, it also enables the problem to be considered more deeply through increased self-exploration. At least 50% of reflections should be complex and go beyond simple repetition (12). Complex reflections refer either to non-explicit content that is inferred or to emotional elements (for example, patient: “I do think my cough comes from smoking.”; physician: “And that worries you.”). In good MI, at least two reflections should be used per question asked.
Third intervention element
Affirmation includes praise (“That’s great that you want to do something about your smoking!”), recognition (“You are going through a difficult time right now.”), and understanding (“I can well understand that you are concerned about the side effects your medication could have.”).
Fourth intervention element
Summarizing is an effective technique whereby the contents mentioned by the patient that are significant for motivation to change are reflected back to the patient (for example, “On the one hand, you don’t want to forbid yourself anything, but on the other, the amount of money you spend on smoking bothers you and your cough worries you”).
Fifth intervention element
MI is characterized in a narrower sense by the encouraging of self-motivational statements. This involves making a distinction between patient utterances that oppose change and suggest a stabilization of the status quo (“sustain talk”; for example, “I don‘t think those 10 cigarettes a day are so bad”) and utterances that make a behavior change more likely in that the patient names reasons and intentions for change (“change talk”; for example, “If I got sick again, I would probably lose my job—maybe I should try the medication after all”). “Change talk” is encouraged by asking specific questions (“How could the medication help you against your depression?”), by affirming (“It‘s impressive that you see a link between the medication and opportunities for your further career”), or by selective reflection (“The medication can help you to stay healthy”) and can be differentiated according to two objectives:
- Building motivation through concrete expressions characterized by the patient stating their desires, abilities, reasons for change, and perceived needs for change, as summarized by the acronym DARN (desire, ability, reasons, and need)
- Stating commitment, activation, and first steps (acronym [CAT] for “commitment,” “activation,” and “taking steps”).
For successful behavior change, it is important that the patient’s need for change translates in the next step into a commitment to change behavior.
Information, as well as the clinician’s own ideas, can be incorporated in MI, whereby it is important to ensure that the patient is prepared to be confronted with the information and that the clinician’s viewpoint is expressed merely as an option and not as the only truth. From a methodological perspective, this is achieved in a three-step process (elicit–provide–elicit) by first asking for consent (“Would you like to know more about...”), secondly, offering the information in a neutral way (for example, “Scientific studies have shown...”), and finally asking the patient for their view (for example, “What do you think about...”). Information that the patient does not want or that they perceive as threatening usually causes reactance.
Conflicts during an interviewing session typically occur when interventions are not suited to the patient’s current motivation to change, for example, when a patient with high-risk alcohol consumption is given recommendations for action, whereas the patient is not yet clear about whether their alcohol consumption constitutes problematic behavior. This can manifest interpersonal dissonance (discord; for example, “Are you trying to imply that I’m an alcoholic?”) or in a reversion to “sustain talk” (“In my case, exercise wouldn’t do any good anyway”). In situations such as these, in addition to treating the patient with empathy, it is particularly important to emphasize their autonomy (“Only you can decide whether you want to change something about that”) (Box 2, 3).
Effectiveness of MI in medical care
Since the approach was first developed, the number of MI-specific publications has increased exponentially, to the extent that there are now more than 1300 randomized trials and around 150 reviews on the effectiveness of MI in a variety of behaviors and target populations. The majority of studies address problematic substance use. By means of a systematic literature search limited to systematic reviews and meta-analyses in the PubMed, Cochrane, and Web of Science databases on the effectiveness of MI in medical care settings using the search terms (“Motivational Interviewing” AND [“primary care” OR “medical care”]), it was possible to identify a total of nine systematic reviews published since 2005, of which two were meta-analyses. Both meta-analyses found small to moderate effect sizes with regard to various health-related behaviors such as blood pressure, substance use, and medication adherence of d =0.18 (95% confidence interval [0.03; 0.33]; p =0.02) (13) and (odds ratio: [OR] = 1.55 [1.40; 1.71]; p <0.001) (14), for the effectiveness of the technique. The included MI interventions varied from single contacts lasting 15 min to long-term treatments lasting up to a total of 480 min, with the majority of studies including brief interventions of no more than three sessions (14). Selected results on individual outcome parameters from the more comprehensive meta-analysis by Lundahl et al. (2013), which covered 48 studies with a total of 9618 included subjects, are shown in the Table (14). Effect sizes represent the improvement in the outcome criterion relative to controls; odds ratios > 1 indicate superiority of the MI group. The practical effect of the intervention is expressed by the binomial effect size display (BESD), in which the probability of success in the treatment group is subtracted from the probability of success in the control group. Values of >50% indicate a greater effect for the condition in question. Particularly marked treatment effects were found for a reduction in substance use, physical inactivity, body weight, and mortality, as well as for improved dental hygiene, acceptance of further treatment, and self-monitoring of health behavior (for example, with regard to blood glucose monitoring and nutrition). No significant effects were seen for eating disorders, self-care behaviors, or individual medical parameters such as heart rate. Effect sizes were greater when the intervention was delivered by the treating clinicians (versus medical/technical assistants). The average treatment effects were significant across all outcome measures, but were most pronounced for patient self-reports (OR = 1.69; [1.55; 1.84]), followed by third-party assessments (OR = 1.48; [1.24; 1.78]), and lowest for biological outcome parameters (OR = 1.18; [1.09; 1.28]) (14). According to Lundahl et al. (2013), effect sizes decrease over time, but five studies with follow-up surveys after more than 13 months nevertheless demonstrate significant effects compared with controls (OR = 1.14; 95% CI [1.03; 1.28]). Treatment effects were significant in waiting lists, as well as in unspecified routine treatments and psychoeducational control conditions.
Reviews of the effects of MI on medication adherence across disorders not limited to medical care found positive, albeit small, effects with a pooled relative risk of 1.17 ([1.05; 1.31]; p < 0.001) (15) and a Cohen’s d of 0.23 ([0.08; 0.37], p > 0.001), with the included studies being of heterogeneous quality (16).
A systematic review of the overall effectiveness of MI across settings and based on 104 published reviews (of which 39 were meta-analyses) found good evidence for cessation or prevention of unhealthy behaviors, particularly with regard to problematic substance use (primarily alcohol, cannabis, and tobacco), whereas the evidence for health-promoting behaviors (except the promotion of physical activity) was more heterogeneous and, in terms of the methodological quality of the studies included, weaker (17). With regard to potential moderator variables, effects were found compared to control groups that had received either no treatment or unspecified routine treatment, but not compared to control conditions with other evidence-based interventions such as cognitive behavioral therapy (17). Although studies on the effectiveness of MI in substance-related disorders point to greater cost-effectiveness for MI compared to other evidence-based interventions (18), corresponding reviews on the cost-effectiveness of MI across disorders are lacking to date (17).
On the basis of the studies conducted to date, MI has proved to be an evidence-based, effective, and comparatively economical method of promoting behavior change in ambivalent patients, particularly in the case of problematic substance use. There are not yet enough studies of high methodological quality available for a variety of other medical fields of application, such as motivation to adopt health-promoting behavior, to be able to make detailed statements on the indication for and differential efficacy of MI.
Mechanisms of MI
With regard to the specific mechanisms of MI, three alternative hypotheses are purported. The technical hypothesis, according to which the effectiveness of MI is achieved through basic skills such as open-ended questions, active listening, affirming, and summarizing in the form of selective reinforcement of patients’ self-motivational utterances, is the hypothesis that has been the most extensively studied to date and, comparatively, has received the most empirical support (19, 20, 21). The relational hypothesis, in contrast, assumes that relationship quality and therapeutic empathy are the most significant factors for the effectiveness of MI. This hypothesis has been investigated to a lesser extent and is deemed to be insufficiently substantiated, with one critical review pointing out that, in the majority of studies considered, the MI clinicians studied differed insufficiently in these characteristics to be able to demonstrate effects on effectiveness (19). The conflict resolution hypothesis states that the effect of MI can be attributed to a large extent to exploration and resolution of conflict, although here again, the empirical evidence is heterogeneous. In their review, Magill and Hallgren (19) conclude that the various factors should be regarded more as necessary than as sufficient conditions for the effect of MI, whereby further research needed.
Conclusions for clinical practice
The MI approach has proved its value for the promotion of intentional readiness for behavior change in a number of behavioral health problems, as well as for the promotion of treatment adherence, and can be used in medical practice even with limited time resources. Continuing education courses on the basic principles of MI, which usually last 2 days, are regularly offered by German Medical Councils and various private sponsors, and specialist literature on different fields of application is available in German (7). A number of German-speaking trainers are members of the international Motivational Interviewing Network of Trainers (www.motivationalinterviewing.org/trainer-listing).
Conflict of interest statement
The authors are members of the international Motivational Interviewing Network of Trainers.
Manuscript received on 14 May 2020, revised version accepted on
8 September 2020.
Translated from the original German by Christine Rye.
Dr. phil. Gallus Bischof
Universität zu Lübeck
Klinik für Psychiatrie und Psychotherapie
Ratzeburger Allee 160
23538 Lübeck, Germany
Cite this as:
Bischof G, Bischof A, Rumpf HJ: Motivational interviewing—an evidence-based approach for use in medical practice.
Dtsch Arztebl Int 2021; 118: 109–15. DOI: 10.3238/arztebl.m2021.0014
This article has been certified by the North Rhine Academy for Continuing Medical Education. Participation in the CME certification program is possible only over the internet: cme.aerzteblatt.de. The deadline for submissions is 18 February 2022.
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