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What is Evidence-Based?

By: Christopher M. Weed, M.A.T., M.S.W. 

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"Evidence-based thinking is a process by which diverse sources of information (research, theory, practice principles, practice guidelines, and clinical experience) are synthesized by a clinician, expert, or group of experts in order to identify or choose the optimal clinical approach for a given clinical situation".2 (p.1)

How to find the evidence?
Once a question or idea is formed, the next step is to find evidence in the form of literature, data or consensus-based guidelines that help to form an approach to answering the question or understanding the idea. There are four basic areas where information is sought in an evidence-based approach to questions or ideas. Data or information can be generated from: Studies which are original reports published in the scholarly literature, Syntheses which are systematic literature reviews of a given topic, Synopses which are study reviews/abstracts with content typically organized in a structured format, often accompanied by a comment, and Systems which are comprehensive data sources of best available evidence from clinical settings.6 (p.57)

Levels of evidence
Within evidence-based thinking, generally there are hierarchical levels of scientific evidence that are generally agreed upon and evidence-based frameworks rely on this hierarchy to help determine the quality of the scientific evidence bearing on a particular condition or service.5(p.114), 1 It can be difficult for a researcher to distill the wide variety and level of information being gathered and as with all research and information gathering, variables can be chosen and overlooked depending on researcher bias. Evidence-based approaches aim to reduce bias, misinformation, stereotyping, discrimination and stigmatization through comprehensive, empirically-based approaches to questions and information. Despite this aim, even the strongest of empirical evidence can still carry influences of systems of belief and privilege.

Below are some commonly agreed upon levels of evidence in order from highest to lowest level of credibility:

Level I: Evidence from true experimental designs
Example: Randomized Clinical Trial is the research design that provides the safest assumptive foundation for inferences about causal relations between interventions and outcomes. An example of randomization is where participants, clinicians, and outcome raters are unaware of who received the experimental and the control conditions. Singular clinical trials can demonstrate a high level of valid data. Repeated clinical trials that produce the same or similar data do even more to strengthen the validity of evidence or data obtained and therefore strengthen the inferences that one might derive from the data obtained.1(p.269), 6(p.61)

Level II: Evidence from quasi-experimental designs
Example: Clinical trials that do not include randomization but do include replication of the same pattern of behavior change across multiple cases or groups given the same intervention. These types of clinical trials offer some evidence of consistency of outcomes but no basis for comparison with other interventions or with control groups where no intervention was introduced.1(p.269),6(p.61-2)

Level III: Evidence from expert consensus
Example: The opinions of multiple respected authorities gathered to form clinical guidelines with some or no basis in research. This level of evidence is often appropriate when there is an absence of clinical studies available on a particular question or idea. This is also a popular form of evidence for practitioners in various fields of clinical work.6(p.62),1(p.269)

Level IV: Evidence from qualitative literature reviews and other publications
Example: Evidence derived from reviews and discussions of previously published literature without a quantitative synthesis of the data, and without clinical information offered in the form of opinion essays, formal case reports, etc.6(p.62)

Level V: Anecdotal information
Example: "Someone once told me…". This category of evidence is made up of various levels of informal information exchange among people interested in a particular question or idea.6(p.63)

How Evidence Gets Into Treatment Practice
In the early 1990s, wide-spread concern developed around the methods and structure of addiction treatment. Some issues of note were: "inadequately trained counselors with large caseloads, inconsistent beliefs about medications and confrontational counseling, treatment plans without behavioral outcomes, and treatment modalities without a clear rationale"3(p.555-6). In order to achieve consistency and improved treatment effectiveness for substance use and addiction, evidence-based treatment began to be developed and studied. In 1999, The National Institute on Drug Abuse (NIDA) established its Clinical Trials Network in order to test evidence-based treatments in actual community practice settings, with program staff delivering the treatment.4(p.2)

Evidenced-based treatment practice has come to be known as treatment which is based on the integration of clinical expertise or experience, clinical evidence derived from systematic research and the characteristics, culture and preferences of the patient or consumer of services.2(p.1), 6(p.53)

Searching for Evidence Based Treatment?
A good reference to consider using when searching for evidence-based substance addiction treatment is the NREPP - The National Registry of Evidence-based Programs & Practices which was initiated in 1998 by the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA). This registry is continually being revised.


  1. Miller, William R., Zweben, Joan, Johnson, Wendy R. Evidence-based treatment: Why, what, where, when, and how? Journal of Substance Abuse Treatment 29 (2005) 267– 276.
  2. Center for Substance Abuse Treatment. Treatment, Volume 1: Understanding Evidence-Based Practices for Co-Occurring Disorders. COCE Overview Paper 6. DHHS Publication No. (SMA) XX-XXXX. Rockville, MD: Substance Abuse and Mental Health Services Administration, and Center for Mental Health Services, 2006.
  3. Amodeo, Maryann, Ellis, Michael A., and Samet, Jeffrey H. Introducing Evidence-Based Practices into Substance Abuse Treatment using Organization Development Methods The American Journal of Drug and Alcohol Abuse. 2006. vol 32: 555–560.
  4. Field appears far from consensus on evidence-based practice Alcoholism & Drug Abuse Weekly Volume 18 Number 18. May 1, 2006.
  5. Hunsley, John Addressing Key Challenges in Evidence-Based Practice in Psychology. Professional Psychology: Research and Practice. 2007, Vol. 38, No. 2, 113–121
  6. McCabe, O. Lee Evidence-Based Practice in Mental Health Accessing, Appraising, and Adopting Research Data. International Journal of Mental Health, vol. 35, no. 2, Summer 2006, pp. 50–69.

This page was last modified on : 10/28/2013

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