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Placebo effects have long been considered nuisances in psychiatry, since their presence can complicate efforts to ascertain the biological mechanisms and efficacies of medication and psychotherapy. However, this view has changed in recent years with increasing recognition of placebo effects' utility in understanding the functioning of various normal brain systems, in elucidating the pathways by which effective treatments for psychiatric disorders may work, and in facilitating the clinical treatment of patients. A new publication by Lidstone and colleagues adds to the growing literature on placebo effects by demonstrating how patient expectancy leads to physiological changes that ameliorate the symptoms of Parkinson's disease (PD).
An influential earlier publication in Science by the same research group was among the first to report an objective basis for placebo effects. Before this work, it was not known whether the observed effects of placebos on a target disorder represented an actual improvement in the disorder or instead reflected a response bias. Based on response biases, patients may report symptom improvement even when the severity of their disorder is unchanged. De la Fuente-Fernandez et al. reported the results of a positron emission tomography (PET) study in which six subjects with PD were given placebo or active medication and asked to rate their symptoms. Dopamine release in the striatum was estimated with PET based on the competition between endogenous dopamine and [11C] raclopride (RAC) for binding to dopamine receptors. The investigators found a significant decrease in striatal RAC binding potential during placebo administration that was comparable