Neural correlates of placebo effect: Review and future implications

Abstract

Experimental and clinical research has documented expectancy related symptom improvement in a variety of conditions, leading to a growing interest in the placebo effect. Despite significant treatment outcomes, placebo-induced effects have been regarded as nonspecific psychological factors associated with the subjective experience of healing that operates different than the actual drug agent . However, neuroimaging research revealed more complex regulation of the placebo response, which indicates a top-down regulation of the symptom improvement enhanced by the expectancy effects. It appears that, placebo response is not solely function of higher order control processes, but also involves diverse disease-specific neurobiological mechanisms. In the current review, neural mechanisms underlying placebo effect have been addressed focusing on the analgesia, Parkinson’s disease and major depression. Along with the opiate system, dopaminergic and serotonergic functions in the brain are discussed in relation with the three target conditions. Last, potential implications of the placebo research are discussed with respect to experimental and clinical practice. 

Keywords

• placebo effect,pain,antidepressants,Parkinson's disease,treatment expectancy

Plasebo etkisinin nöral temelleri: Geçmiş bulguların gözden geçirilmesi ve çıkarsamalar

Öz

İyileşme beklentisi ile ilişkili hastalığa-özgü semptomlardaki iyileşme literatürde sıkça gösterildiğinden plasebo etkisine olan ilgi giderek artmaktadır. Her ne kadar tedavi etkinliği plasebo gruplarında belirgin olsa da, bu etkinin asıl maddeden ziyade, hastanın iyileşme beklentisi ve öznel iyilik değerlendirmesinin bir sonucu olarak düşünülmektedir. Öte yandan, beyin görüntüleme çalışmaları daha karmaşık bir sürecin var olduğuna işaret etmektedir. Denetimli kontrol mekanizmalarının yönettiği plasebo etkisinin iyileşme beklentisi ile güçlendiği görüşü giderek ağırlık kazanmaktadır. Bu bağlamda görünen odur ki, plasebo etkisi tek bir sistem üzerinden değil, hastalık temelli mekanizmalar aracılığı ile ortaya çıkmaktadır. Bu derleme çalışmasında da, plasebo etkisinin nöral boyutlarının sıkça incelendiği ağrı, Parkinson ve depresyon olgularına ilişkin bulgulara odaklanılmış ve opiat sistemi ile dopaminerjik ve serotonerjik işlevler incelenmiştir. Bu doğrultuda da, geçmiş bulguların gözden geçirilmesinin ardından plasebo etkisinin gelecek çalışmalardaki rolü tartışılmıştır.

Anahtar Kelimeler

• Plasebo etkisi,ağrı,antidepresanlar,Parkinson,tedavi beklentisi

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