Effect of the placebo control condition in neuroendocrine challenge studies

Neuroendocrine challenge studies are frequently used to make inferences about the pathophysiology of psychiatric illness or about the effects of chronic psychotropic drug treatment on brain monoamine function. The outcome of these exploratory neuroendocrine tests, however, may be influenced by the effects of confounding variables, such as specific stress effects and variations in basal hormone levels. The inclusion of a placebo control condition minimizes the variability due to these variables. A number of recent neuroendocrine studies have omitted the placebo control condition. Based on experimental data, it can be shown that failure to include a placebo control condition may result in both Type I and Type II errors of inference. These results suggest a placebo control condition should be included in exploratory neuroendocrine challenge studies.