Placebo is defined as a substance or method that has no specific effect on the condition being treated. Placebo leads to the state of contentment and shows its effects just like a drug by the pathways in the body. Various changes formed by plasebo on the brain activation, neurotransmitters and hormones have been observed with the development of neuroimaging methods. The effects of dopamine, serotonin, and opioid systems in the formation of the placebo response; the relationship between placebo effect, reward cycle and expectation process and the role of the some specific regions in the brain where pharmacological agents acting on during the placebo response have been shown in several studies. There are similarities between hypnosis and the placebo effects and expectation of improvement is closely related to the suggesting phenomenon in the hypnosis as well as placebo responses. The formation of similar changes in the brain after administration of placebo and hypnosis associated with the expectation models and suggestions attracts attention. Neurochemical pathways in the brain constitute functional impact with many of the common mechanisms. Therefore, all of these mechanisms in the placebo response can take part in relation to each other. Although it is known that many factors may influence, understanding of the effects of placebo and viewing the changes in the brain formed by placebo have an important place for enlightening roles of psychological factors in the onset of diseases and treatment.
Placebo effect, neurobiology, anticipation and reward models.