It is important to define precisely what is and is not meant by "empirically supported treatments," rigorously based on what is actually known about the nature of experimental therapy research. The criteria for empirically supported treatments merely allow conclusions about whether treatments cause any change beyond the causative effect of such factors as placebo or the passage of time. Applied implications are limited, due to external validity and to the fact that applied decisions are influenced by cost–benefit analyses. Creating increasingly effective therapies through between-group designs is best done by controlled trials specifically aimed at basic questions about the nature of psychological problems and the nature of therapeutic change mechanisms. Naturalistic research is important for external validity but is valuable only if it uses scientifically valid methods to address basic knowledge questions.