Did you know that most of the benefits of antidepressants in the treatment of depression and anxiety are due to the placebo response (Kirsch, 2019)? In other words, the active ingredients in some medications are nowhere near as effective as the implementation of expectations and psychological hints.
Placebos are substitutes for drugs or treatments which produce similar beneficial effects without the active ingredients or intervention. Such placebo effects are the results of the psychological responses to the context in which a treatment is delivered rather than to the specific actions of the treatment. For example, if a doctor gave one group of patients sugar pills and another group actual medicine, and both groups recover just as well, it is not the chemical composition of the medicine that helped the patients, but the action of taking a pill giving the patient the belief that they are getting effective treatment. The belief in the placebo can bring about a wide range of positive impacts depending on the context, from relieving pain and stress to enhancing memory and creativity (Rozenkrantz et al., 2017). In contrast, there are also nocebo effects (Turi et al., 2018), where negative expectations of treatment diminish its beneficial effects.
The weird power of the placebo effect, explained. (Image from Vox.com)
So how exactly do placebo effects arise? The keyword here is expectation – developed through “personal experiences (learning), observational learning, instructions or information from doctors and other clinical staff, information from other sources such as the Internet, or personal beliefs” (Petrie & Rief, 2019). For instance, if you have taken an ibuprofen pill before to relieve a headache, you have learnt how helpful it is, and expect the same thing to happen if you took another pill that looks exactly like the previous ibuprofen pill. The mechanism could also be explained by classical conditioning – just like dogs associate bell sounds with food and start to drool as soon as they hear the bell ringing, we associate contexts such as the presence of doctors and syringes to the active treatments and our bodies react accordingly.
Research shows that an individual’s response to a placebo is influenced by many factors. Biologically, there are neurotransmitter pathways in our brains that mediate our response to placebo effects, and variations in these pathways may correlate with different genetic makeups (Hall et al., 2015). Besides that, personal and socio-cultural factors also play a role. For instance, Blackwell et al. (1972) study has suggested that participants showed greater response to two sugar pills than one sugar pill, due to the expectation that two pills indicate a stronger dosage. In the same study, it was also found that the pink pills were better for improving concentration than blue pills. The researchers hypothesized that the difference can be attributed to the cultural meanings of the two colours – the colour pink tends to be more frequently associated with alertness while blue is associated with calmness and relaxation.
Due to evidence which indicates that placebos can induce meaningful responses in patients, it has then been suggested that doctors could use more placebo drugs when treating patients, for their similar benefits and without the side effects. Although this could pose potential ethical concerns in terms of deception towards patients, research has also shown that deception is not necessary for placebo drugs to replace active medication. According to a study by Charlesworth et al. (2017), even when patients know they are not taking actual medicine but merely placebos, the sugar pills can still be effective as long as they are accompanied by a rationale in which it was explained that placebos can be effective.
Besides the application of placebo drugs in medical treatment, understanding the placebo effect is also vital in scientific research. Placebos are commonly used in experiments as the control condition. For example, if we are injecting a type of medication in participants in the experimental condition to see if it can effectively improve, we want to inject saline in the control condition instead of no injections. If the control condition had no injections, the difference in results of the two conditions could then be attributed to the act of injection instead of the medication. Any difference between the control condition and experimental condition would become a confounding factor as they would give the participants different expectations.
It has been suggested that we should try to match the expectations of the two conditions as much as possible with the help of placebos (Boot et al., 2013). This also denotes the importance of carefully operationalized double-blind procedures, where both the experimenter and the participants should not have the knowledge about which individuals are assigned to which conditions. Although many studies claim to be double-blind, many times the procedure can be prone to the phenomenon of breaking blind. A study has shown that even when a placebo was used, 78% of patients and 87% of the doctors could accurately identify whether the patients had been given an active drug or a placebo, and when participants accurately identified that they were in the placebo condition, the placebo effect is reduced (Rabin, as cited in Kirsch 2019). It has thus been proposed that doctors’ and patients’ opinions on their condition assignment should be recorded before and after experimental trials to see whether blind breaking occurred. This same strategy could be applied in the context of psychological research in general to reduce demand characteristics, which just like placebo effects, promote expectations of how the experiment is supposed to go.
In conclusion, the placebo effect is an intriguing phenomenon of how psychological expectation can result in biological and cognitive responses. Understanding the mechanism of placebo can be beneficial in terms of medical treatment as well as general scientific research.
References
Blackwell, B., Bloomfield, SaulS., & Buncher, C. Ralph. (1972). Demonstration to medical students of placebo responses and non-drug factors. The Lancet, 299(7763), 1279–1282.
Boot, W. R., Simons, D. J., Stothart, C., & Stutts, C. (2013). The Pervasive Problem With Placebos in Psychology. Perspectives on Psychological Science, 8(4), 445–454.
Charlesworth, J. E. G., Petkovic, G., Kelley, J. M., Hunter, M., Onakpoya, I., Roberts, N., Miller, F. G., & Howick, J. (2017). Effects of placebos without deception compared with no treatment: A systematic review and meta-analysis. Journal of Evidence-Based Medicine, 10(2), 97–107.
Hall, K. T., Loscalzo, J., & Kaptchuk, T. J. (2015). Genetics and the placebo effect: The placebome. Trends in Molecular Medicine, 21(5), 285–294.
Kirsch, I. (2019). Placebo Effect in the Treatment of Depression and Anxiety. Frontiers in Psychiatry, 10(407).
Petrie, K. J., & Rief, W. (2019). Psychobiological Mechanisms of Placebo and Nocebo Effects: Pathways to Improve Treatments and Reduce Side Effects. Annual Review of Psychology, 70(1), 599–625.
Rozenkrantz, L., Mayo, A. E., Ilan, T., Hart, Y., Noy, L., & Alon, U. (2017). Placebo can enhance creativity. PLOS ONE, 12(9), e0182466.
Turi, Z., Bjørkedal, E., Gunkel, L., Antal, A., Paulus, W., & Mittner, M. (2018). Evidence for Cognitive Placebo and Nocebo Effects in Healthy Individuals. Scientific Reports, 8(1).
