Placebo effects in Psychology

The history of prescientific medicine is in fact the history of the placebo effect, as most, if not all, treatments were nothing but placebos, that is, treatments devoid of specific therapeutic properties. However, it was not until placebos began to be used as controls in clinical trials that they became a mainstay of modern medicine. The most productive models to better understand the neurobiology of the placebo effect are pain, motor disorders, fatigue, and both immune and endocrine systems. In these conditions, several neurotransmitters have been identified, such as endogenous opioids, cholecystokinin, and dopamine; lipidic mediators, for example endocannabinoids and prostaglandins; some immune mediators; and some hormones. One of the main implications of the recent advances in placebo research is the gradual improvement of our understanding of how procedural interventions can bring the placebo response under control. This can be used to maximize it to the patient’s advantage in clinical practice and minimize it in clinical trials for the evaluation of active principles. The other implication is the possibility to induce drug-like effects without drugs (for example, by having doctors use positive language with patients), thus opening up the potential of reducing drug intake. In both cases, the ethical implications are far from being resolved and might require an in-depth methodological and ethical discussion.