In contrast to classical conditioning of physiological responses such as immune responses and drug effects, only a limited number of studies investigated classical conditioning of endocrine... Show moreIn contrast to classical conditioning of physiological responses such as immune responses and drug effects, only a limited number of studies investigated classical conditioning of endocrine responses. The present paper is the first systematic review that integrates evidence from animal and human trials regarding the possibility to condition the endocrine responses. Twenty-six animal and eight human studies were included in the review. We demonstrated that there is accumulating evidence that classical conditioning processes are able to influence specific endocrine responses, such as cortocosterone/cortisol and insulin, while more limited evidence exists for other hormones. Animal and human studies were generally consistent in their findings; however, the limited number of human studies makes it difficult to generalize and translate the results of animal research to humans. Next to methodological recommendations for future studies, we suggest several ways how classically conditioned endocrine responses can be used in clinical practice. Show less
Introduction: Placebo effects are powerful modulators in clinical outcomes and can either result in treatment benefits or harms, known as placebo and nocebo effects. To harness these outcomes, it... Show moreIntroduction: Placebo effects are powerful modulators in clinical outcomes and can either result in treatment benefits or harms, known as placebo and nocebo effects. To harness these outcomes, it is important to focus on the underlying processes that steer these effects, namely by learning through expectations and conditioning. In this review, we focus on the influence of placebo effects on subjective and physiological levels of immune-related conditions (e.g. lymphocyte proliferation, cytokine production or other inflammatory markers).Areas covered: A literature search is conducted in the databases PubMed and PsychInfo by making use of keywords such as ‘expectations’, ‘classical conditioning’, ‘cytokines’, ‘immune system’, ‘learned immunosuppression’, and covers studies done in animals, experimental studies in healthy controls as well as studies performed in immune-related patient populations.Expert commentary: We report on the presence of placebo effects in RCTs in immune-related conditions and review findings that demonstrate the ability to learn immune responses in both experimental animal and human placebo studies making use of conditioning paradigms with immunomodulating drug agents. We also discuss results to utilize placebo effects by means of classical conditioning principles in medication regimens for patient populations and elaborate on promising findings of preliminary studies focusing on this topic. Show less
