The effectiveness of many psychotherapeutic treatments has been established through sufficient scientific support. However, for many treatments the research is still emerging, inconsistent or nonexistent. To understand the evidence-base for particular treatments, it is essential to appreciate the different levels of evidence that can be used to determine whether a treatment is effective.
The evidence pyramid below presents a hierarchy of study types, based on the rigor of the research methodology.
Levels of Evidence to Inform Practice
The VA/DoD Clinical Practice Guidelines
Evidence-based clinical practice guidelines (CPGs) reflect the highest standard for appraising the scientific evidence base to inform health care practices  . CPG developers evaluate both the quality and volume of the available research evidence to recommend particular treatments. The Veterans Health Administration (VHA) and Department of Defense (DoD) CPGs are developed using systematic, well-established and transparent methods to evaluate different treatments across a range of mental health conditions  . The VA/DoD CPGs are intended to improve care by reducing variation in practice and systematizing “best practices.” Based on their rigorous methodology, the VA/DoD CPGs provide the best appraisal of the evidence and should be a primary resource when choosing an evidence-based treatment.
Systematic reviews reflect one of the highest standards in evidence-based health care and directly inform clinical practice guidelines (CPGs). The systematic review methodology, as explicitly outlined in a report from the Institute of Medicine (IOM), “Finding What Works in Health Care: Standards for Systematic Reviews,”  relies heavily on systematic, rigorous and transparent processes to answer key questions on the state of the science for particular treatments.
Randomized Controlled Trials
A randomized controlled trial (or RCT) is the next level of scientific evidence and is considered the gold standard for research evaluating the effectiveness of psychotherapeutic interventions. RCTs aim to reduce bias by randomly allocating participants to different treatment groups. Randomization allows investigators to better detect true effects of a treatment, while keeping other variables constant.
IOM. (2011). Clinical Practice Guidelines We Can Trust. Retrieved from https://www.nap.edu/catalog/13058/clinical-practice-guidelines-we-can-trust.
 IOM. (2011). Finding What Works in Health Care: Standards for Systematic Reviews. Retrieved from https://www.nap.edu/catalog/13059/finding-what-works-in-health-care-standards-for-systematic-reviews.