Based on the high amount of empirical evidence in the field of placebo effects, the interest of the scientific community has shifted from the mere content of the placebo agent to its active mechanisms in simulating and modulating the efficacy of a therapy. Indeed, placebo effects consist of complex mechanisms that are active anytime a patient receives a treatment whether inert, or in combination with a pharmacological effect. The negative counterpart is the nocebo effect, i.e., an adverse event resulting from negative expectations and beliefs, which can lead to a worsening of the disease and lower effectiveness of therapies. Patient learning, expectations and needs, the environmental and clinical setting, and the doctor-patient relationship are key elements involved in placebo/nocebo effects.