Most, but not all, published reviews of the literature have concluded that ECT is effective in the treatment of depression. In 2006, research psychiatrist Colin A. Ross reviewed the entire body of placebo-controlled literature on ECT and found that no study showed a significant difference between real and placebo ECT at one month post-treatment. The review also found that many of these studies failed to find a difference between real and placebo ECT even during the period of treatment. Based on these observations, Dr. Ross concludes that "claims in textbooks and review articles that ECT is effective are not consistent with the published data", and that consent forms for the procedure should state that "real ECT is only marginally more effective than placebo." The review was highly critical of other published reviews concluding that ECT was effective, because these reviews often relied primarily on studies that were not placebo-controlled.^[18]