Placebo Effect: The Stem of Seminal Studies with Active Treatment Neurobiological Mechanisms, And Implications for Parkinson’s Disease with Deep Brain Stimulation

Despite long standing controversies about the therapeutic validity of placebo due to its administration of inert substances, placebo emerges for its efficacy to amplify the therapeutic benefits of active medical interventions through patients’ psychological beliefs and expectations. Advances in neuroimaging and utilization of hormonal agonists have elucidated underlying brain mechanisms and biochemical pathways such as the endogenous opioid systems. This research synthesizes pivotal studies on placebo effect, including Beecher’s 1995 analysis; whereas, Hróbjartsson and Gøtzsche’s 2001 meta analysis refuted its clinical significance. In-depth interaction in the assumption of additivity between placebo and active treatment as well as deep brain stimulation in Parkinson’s Disease reveals the placebo’s prominence in brain reward mechanisms. Moreover, placebo mechanisms induce significant neurotransmission in the endogenous opioid systems and several brain regions including periaqueductal gray. Further inquiries are necessitated for precision in examining the role of expectation, emotions, interactions with test administrators, as well as genetic levels.