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Meta-analytic review of control groups in anxiety research: An investigation for resolving the methodological and ethical dilemma

12 December 2003


Both wait-list and placebo control groups represent a homogenous problem in conducting effectiveness research. Each is considered a methodological necessity, while at the same time being viewed as an ethically undesirable aspect of research. The present study attempts to satisfy both the ethical requirement to treat research subjects humanely and the rigors of scientific methodology. Effect sizes were calculated for wait-list and pill placebo controlled anxiety outcome studies. Data were analyzed from 36 studies including 1,439 unique subjects in an attempt to establish the improvement or deterioration of individuals in control conditions of anxiety treatment research. Data analyses determined subjects in anxiety outcome research assigned to the wait-list control condition demonstrated very little improvement regardless of anxiety diagnosis or time in the control condition. Data analyses also determined that subjects in the pill placebo control condition demonstrated significant improvement, with the greatest improvement during the first six weeks of the placebo condition. Further, the current study established posttraumatic stress disorder as the most responsive (i.e., demonstrated the greatest improvement) diagnosis, and obsessive-compulsive disorder as the disorder demonstrated the least improvement regardless of control condition


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