Final answer:
The placebo effect is a psychologically based reaction to a treatment that alters conscious and unconscious expectations. It occurs when a person believes that a treatment will be effective, and this belief can affect their health outcome.
Step-by-step explanation:
The placebo effect is a psychologically based reaction to a treatment that occurs just because the subject is treated, even if the treatment is a placebo that has no physiological effect on the patient.
Placebos have such a strong effect on people because they alter conscious and unconscious expectations. When a person believes that a treatment will be effective, this belief can affect their health outcome. The power of suggestion and the expectation of the study participant can be as important as the actual medication.