Evidence-Based Practice: Three-Legged Stool or Filter System?

By David F. Tolin, Ph.D., ABPP



The concept of evidence-based practice (EBP) in mental health has become more influential than ever over the past decade.  The APA Presidential Task Force on Evidence-Based Practice (2006) defined EBP as consisting of three components of information: best available research evidence, clinical expertise, and patient characteristics.  This definition, borrowed from the Institute of Medicine (2001), seems quite reasonable at first glance, but, as is often the case in our field, much is left open to interpretation.  Therefore, one psychologist’s EBP might not resemble another’s.

In many cases, the three components of EBP are treated equally, as shown in Figure 1.  In this “three-legged stool” conceptualization (Spring, 2007), research evidence, clinical expertise, and patient characteristics are all weighted equally, and are expected to have comparable effects on the overall outcome.  One significant problem with this conceptualization is the fact that the three components often don’t line up—for example, my clinical experience might be different from the best research evidence—and the practitioner is given little guidance about how to make appropriate treatment decisions in such cases.


I suggest that these three components (all of which are important) play different critical roles in clinical decision-making (see Figure 2).  The basis of clinical decisions is the best available research evidence.  Clinical expertise and patient characteristics serve as filters through which the research evidence is interpreted, adjusted, and implemented.

That is, a skilled evidence-based practitioner will first identify the treatment with the strongest scientific evidence base for the problem most closely matching that of the patient or client.  That treatment may subsequently be adapted or augmented, based on patient characteristics such as comorbid psychopathology, situational factors, patient preferences, or demographic features.  Such selection, adaptation, and augmentation procedures derive from the expertise of the clinician.

Importantly, in this model clinical expertise and patient characteristics do not trump the best available research evidence, nor are the three factors be considered an “either-or” selection.  That is, skillful EBP does not involve selecting a treatment based on research evidence or the clinician’s expertise or on patient characteristics.  Rather, the best available research evidence forms the basis of clinical judgment, with additional selection and modification based on clinical expertise and patient characteristics.


EBP is rapidly evolving from an option to an obligation for practitioners as the Affordable Care Act (“Patient Protection and Affordable Care Act,” 2010) influences treatment considerations.  However, clinical psychology may be behind the curve in this process: Many clinical psychologists practice what they learned in graduate school, rather than being informed by research findings (Cook, Schnurr, Biyanova, & Coyne, 2009).  Indeed, our use of research findings lags markedly behind that of physicians (Carlsen & Bringedal, 2011),including psychiatrists (Mullen & Bacon, 2004).  A better understanding of EST, and how research, clinical expertise, and patient characteristics can inform practice decisions, will help psychology lead the way to 21st century mental health care.

I’d love to hear your comments about EBP.  Write in to the Division listserv (div12apa@lists.apa.org), or email me directly at david.tolin@hhchealth.org.


APA Presidential Task Force on Evidence-Based Practice. (2006). Evidence-based practice in psychology. American Psychologist, 61(4), 271-285.

Carlsen, B., & Bringedal, B. (2011). Attitudes to clinical guidelines–do GPs differ from other medical doctors? BMJ Qual Saf, 20(2), 158-162.

Cook, J. M., Schnurr, P. P., Biyanova, T., & Coyne, J. C. (2009). Apples don’t fall far from the tree: influences on psychotherapists’ adoption and sustained use of new therapies. Psychiatric Services, 60(5), 671-676.

Institute of Medicine. (2001). Crossing the quality chasm: A new health system for the 21st century. Washington, DC: National Academy Press.

Mullen, E. J., & Bacon, W. (2004). A survey of practitioner adoption and implementation of practice guidelines and evidence-based treatments. In A. R. Roberts & K. R. Yeager (Eds.), Evidence-based practice manual: Research and outcome measures in health and human services (pp. 210-218). New York: Oxford University Press.

Patient Protection and Affordable Care Act, 42 U.S.C. § 18001 et seq. (2010).

Spring, B. (2007). Evidence-based practice in clinical psychology: what it is, why it matters; what you need to know. Journal of Clinical Psychology, 63(7), 611-631. doi: 10.1002/jclp.20373