The Placebo Effect: What Is It?
The placebo effect occurs when people believe a drug, surgery or other treatment will make them feel better. It is also known as the "dummy" effect. It has been used in clinical trials since the early 20th century.
Placebo effects are important to understand for both clinicians and neuroscientists, as they are substantial across diverse disorders2-3 and may be influenced by treatment context rather than specific active treatments4.
Patients have a range of contextual information that surrounds and influences their treatment experiences. This includes treatment, place and social cues as well as verbal suggestions. The patient's brain interprets this information and combines it with memories, emotions and expectancies. It then constructs a picture of the meaning of the treatment context in terms of future survival and well-being.
Conceptual processes are involved in the generation of expectations and appraisals and can be mediated by affective states, decisions and behaviour, while pre-cognitive associations influence physiological processes that are outside conscious control. These two types of processes combine to make up the 'treatment context' and are 'active ingredients' of all types of placebo effects4.
The Impact of Expectations on Placebo Effects
The placebo effect is a psychological process in which a person believes a medication or other treatment will improve their health. This can be caused by a number of things, including the belief that a treatment will help their condition, or the excitement of receiving a new drug.
Some studies have shown that the body's chemistry can change after taking a pill that has no actual therapeutic benefits, causing participants to report improvements in their heart rate, blood pressure and mood. This is often accompanied by changes in brain activity, such as enhanced attention and memory, as well as reduced stress and pain.
It is a complex process, but some researchers have found that it's possible to predict the amount of placebo effect that a person will experience before they take a drug or other treatment. For example, people who expect a stimulant-type drug to give them energy are more likely to get a high after taking the pill, while those who expect the same drug to relax them are more likely to report that they are feeling less stressed after taking the medication.
Influence of Expectations and Research Bias
Believing a drug will work is the most important part of the placebo effect, but it is not the only factor. The placebo effect can also be triggered by the enthusiasm of researchers, who want to share their findings with patients and are therefore more likely to exaggerate the effects of the drug they're testing.
The placebo effect has also been linked to changes in the brain's ability to recognize and respond to pathogens. The brain uses a set of rules to decide when it will trigger a response to a pathogen, for instance, by raising the body's temperature to fight off bacteria or viruses. This can be useful in fighting off infection, but it can also lead to other side effects, such as overheating or a dangerous increase in the heart rate.
