Placebo Effect
The placebo effect is known to contribute substantially to treatment outcomes in both medical research and clinical practice. This is important for optimizing drug development and clinical care.
Placebo analgesia is the most full-bodied and most researched form of the placebo effect. However, many studies have varying results. Small group sizes hinder the detection of minor to moderate effects and make it difficult to determine which structures are altered by placebo.
People who reported the most pain relief when taking a placebo also have less brain activity in areas of the brain related to pain. This was found in a systemic meta-analysis recently published in the journal Nature Communications.
The results of the study provide new insight into placebo effects on pain-related brain activity and may have inferences for clinical care and drug advance.
Placebo effect analysis
Brain images were analyzed at an individual level through the analysis of 20 studies, a total of 603 participants.
The studies used looked at evoked pain under stimulus intensity-matched placebo and control conditions. Placebo conditions were defined as conditions where the experimental context suggested that an effective analgesic treatment was applied, including :
- verbal suggestions
- conditioning procedures that reinforced participants’ expectations of reduced pain
Under control conditions, the participants received analgesic treatment. It was not clear to the participant himself which conditions were applied. The participants indicated whether they felt less pain. It was then investigated whether this could be correlated to certain brain regions. In addition, it was examined whether a possible brain response was meaningful.
Outcomes
A placebo causes small, widespread reductions in pain-related activities in the brain. It was found that individuals with the most pain relief also had the greatest reduction in brain activity.
The change in activity was found in the thalamus, somatosensory cortex, basal ganglia, and posterior insula.
Activation of the prefrontal cortex is heterogeneous in all studies, meaning that no specific areas in this region were consistently activated. The prefrontal cortex is triggered in expectation of pain. It helps keep track of the context of the pain. It also maintains the belief that pain exists. These differences between the studies analyzed are similar to what is found in other brain regions of self-regulation.The same region where different types of thoughts and mindsets can have different effects
Inference
We can conclude that placebo effects are not only restricted to sensory/nociceptive or cognitive/effective procedures but probably include a blend of mechanisms that may vary dependent on the placebo paradigm and other individual factors. The findings will contribute to future research in the development of brain biomarkers that predict whether an individual will respond to a placebo. In addition, they will also help differentiate between the effect of a placebo and a pain reliever.
Understanding the neural pathways underlying the placebo effect will pave the way for us to use the placebo effect systematically in a context-, patient- and disease-specific manner, the researchers say. We can use the placebo effect in a drug, surgery, or other treatment, as it could potentially improve treatment outcomes.
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