The potential for a placebo response varies widely depending on the medical condition placebo administration is applied to. It appears that conditions involving bothersome (non-life threatening) symptoms such as mild depression, mild anxiety, chronic pain, and gastrointestinal issues are good indications to experience a placebo effect. This has been shown in several studies. e.g., (Kirsch, 2008). When it comes to performance enhancement, studies show good placebo responses for ADHD, chronic fatigue syndrome, Parkinson’s disease, and also erectile dysfunction (ED). More about that in the chapter “Placebo Value”.
Regarding self-healing, there are some interesting computer models and studies that support the idea that placebos can be designed to beneficially influence the immune system. More about that in the chapter “How placebos work.”
The design of placebo pills is an essential element for an effective placebo experience. Studies show that pill features such as the color and size matter for a patient’s response to the treatment. A review of twelve studies (de Craen, 1996) looked into participants’ perception of how drugs act, depending on pill colors. The results showed that patients usually associated red, orange and yellow colors with a stimulant effect, while they associate green and blue colors with tranquilizing effect. An exception to this rule was observed in study participants from Italy. Blue is the color of Italy’s national sports teams.
In most cultural settings, green and blue color produce a calming placebo effect.
Placebo Price and Symptom Relief
Here is an interesting study about placebo pricing and symptom relief (Waber 2008). Dan Ariely, a behavioral economist at Duke University showed in a study with 82 healthy volunteers that price matters. All participants got a painful stimulus – they were given electric shocks. They were then offered a placebo pill for pain relief. The price of the placebo mattered for pain relief:
- 85% of volunteers who took placebos priced at $2.50 per pill experienced pain relief
- 61% experienced pain relief who took the same pill, but priced at 10 cents
That’s more than a 20% difference between groups.
Price really matters for symptom relief from placebos.
Placebo Price and Performance
In another study, researchers measured the number of words that healthy study participants were able to unscramble after consuming a branded soft drink (Shiv, 2005). One group of participants was told that studies showed such drinks create large improvements in mental functioning. A second group was told that these drinks only provide a slight improvement in performance. Participants were also told about the cost of the drink. Half of the participants in each group were told that the drink costs $1.89, while the others believed the drink’s price was just 89 cents. Finally, the third group performed the word-unscrambling test without learning about the drink at all. Here are the results:
- An average member of the control group unscrambled 7 words within the time given.
- The group that thought the drink was only slightly effective and was cheap unscrambled 4 words.
- The group that thought the drink was very effective and high priced got over 10 words.
More expensive placebos produce better mental performance.