There are 3 types of support for CAM therapies: Efficacy on clinical outcomes as shown in controlled clinical trials (considered the strongest evidence for clinical uses) Evidence of established physiologic mechanisms of action (eg, modification of gamma-aminobutyric acid [GABA] activity in the brain by valerian), although evidence of a validated physiologic mechanism of action does not necessarily indicate efficacy on clinical outcomes Use over periods of time ranging from decades to centuries (considered lower quality evidence) A substantial amount of information about CAM is available in peer-reviewed publications, evidence-based reviews, expert panel consensus documents, and authoritative textbooks; much of it has been published in languages other than English (eg, German, Chinese).