"Gibbs (2003) and others (e.g., Straus, Richardson, Glaziou, & Haynes, 2005) have provided detailed suggestions in this regard. Some general principles for clinicians are as follows. Evidence from multiple studies is always preferred to results of a single study. Systematic reviews of research are preferable to traditional narrative reviews. Thus, clinicians should look for systematic reviews, mindful of the fact that these reviews vary in quality. The Cochrane and Campbell Collaborations are good sources of high-quality systematic reviews. Clinicians can and should assess potential sources of bias in any review. The characteristics of systematic reviews described in this chapter can be used as a yardstick that clinicians can use to judge how well specific reviews measure up. The QUOROM statement (Moher et al., 1999) provides guidance about what to look for in reports on systematic reviews, as does a recent report by Shea et al. (2007). When relevant reviews are not available, out of date, or potentially biased, clinicians can identify individual studies and assess the credibility of those studies, using one of many tools developed for this purpose (e.g., Gibbs, 2003). It would be ideal if clinicians were able to rely on others to produce valid research syntheses. Above all, clinicians should remember that critical thinking is crucial to understanding and using evidence. Authorities, expert opinion, and lists of ESTs provide insufficient evidence for sound clinical practice. Further, clinicians must determine how credible evidence relates to the particular needs, values, preferences, circumstances, and ultimately, the responses of their clients. Clinicians and researchers also need to have an effect on policy so that EBP is not interpreted in a way that unfairly restricts treatments. Policymakers and others can be educated about the nature of EBP. EBP is a process aimed at informing the choices that clinicians make. It should inform and enhance practice, "increasing, not dictating, choice" (Dickersin, Straus, & Bero, 2007, p. s10). EBP supports choices among alternative treatments that have similar effects. It supports the choice of a less effective alternative, when an effective treatment is not acceptable to a client. Policymakers and others can be educated about the nature of evidence and methods of research synthesis. Empirical evidence is tentative, and it evolves over time as new information is added to the knowledge base. At present, there is insufficient evidence about the effectiveness of most psychological and psychosocial treatments (including some so-called empirically supported treatments). Policymakers need to understand that most lists of effective treatments are not based on rigorous systematic reviews; thus, they are not necessarily based on sound evidence. It makes little sense to base policy decisions on lists of preferred treatments because this limits consumer choice. Lists of selected or preferred treatments should not restrict the use of other potentially effective treatments. Policies that restrict treatments that have been shown to be harmful or ineffective, however, are of benefit. Lists of harmful or wasteful treatments could be compiled to discourage their use."