Lessebo effect: what it is and how it affects research

In clinical trials with a randomized control group, the extent to which belief in an experimental treatment influences the degree of improvement reported by volunteers should be measured.

The placebo effect is widely known in research, which can be defined as the improvement perceived by participants who think they have received an effective treatment, although this is not the case.

However, the placebo effect is not the only one that can occur in such trials. The lessebo effect, as well as the nocebo, are also a product of suggestion.. Below we will see what the lessebo effect is, in addition to relating it to the other two.

    The lessebo effect and the relationship with research

    In science, when creating a new clinical intervention, whether it’s a drug, a new type of therapy, or a whole new treatment, you first need to check if it really works. This is why it is common for clinical trials to be conducted involving volunteer participants who have the medical or psychiatric condition that the new intervention is supposed to improve.

    However, in order to correctly detect the therapeutic capacity of the new intervention, it is normal that in these trials there is at least two groups: one experimental and one control. The experimental group will be made up of participants who will receive the intervention, with the intention of seeing what effects it has on their health, if there is improvement or worsening of symptoms. In contrast, participants in the control group will not receive any therapeutic treatment. Participants in the control group and those in the experimental group do not know which group affected them.

    The purpose of forming these two groups is to get to know each other to what extent the improvement (and also the worsening) of the participants is attributable to the implementation of the intervention.

    The idea is that if there is an improvement in the experimental group and not in the control group, the improvement is due to the treatment. In the event that there is some type of improvement in both groups, it will not be related to the intervention, but attributable to the evolution of the medical or psychiatric condition that needs to be treated. This is because there are medical illnesses and mental disorders that may just get better over time.

    Let’s start with the principle: the placebo effect

    So far everything makes sense, but one question surely comes to my mind: if the experimental group receives the treatment to be tested, what does the control group receive? The volunteers in the control group should be given something, otherwise they will know that they are part of such a group and that is something we do not want. What we want in research is to verify the pure and simple effectiveness of the treatment, and for this it is necessary that those who receive do not know that they are receiving it but that they show an improvement if it is effective.

    For this reason, all participants in the experiment receive something. If an experimental treatment is applied to the experimental group, a placebo is applied to the control. A placebo substance or treatment is any intervention that those who apply it know or assume it has no effect, neither therapeutic nor harmful. For example, in pharmaceutical research, if the experimental group receives the drug that is supposed to work, the witness will receive something that looks like a drug, in the form of a pill or a syrup, but without any active component.

    And this is where we have to talk about the placebo effect. This effect is essential to take into account in research, as it could well call into question the effectiveness of the new intervention. The placebo effect occurs when the control group, although not receiving an experimental treatment, reports improvement. Participants in the control group expect to have received the experimental treatment and believe it is being applied to them, perceiving an improvement that is nothing more than a suggestion.

    It is important to understand that before participating in an experiment, participants receive informed consent. He explains that the experimental treatment being tested can have both health benefits and side effects, and that the point of the experiment is to find out what they are. In addition, they are told that they can receive this treatment or that they can be given a placebo. Despite knowing this information, it is not uncommon for participants to wish to be part of the experimental group, and to believe that this group touched them, feeling a supposed improvement.

    The use of placebo is the norm in randomized controlled trials. The logic behind the application of placebos stems from the need to distinguish between the actual benefit observed by the participant and the benefit which is the product of his desire to improve. The mind is very powerful and is capable of deceiving us, masking the symptoms, and making us believe that we have improved.

    Although the placebo effect has been known for some time and research, both medical, pharmaceutical, psychological and psychiatric, has questioned it, it has been suggested that there are two other effects given in a context experimental: the nocebo effect and the lessebo effect. Both effects are of great importance, as is the same placebo effect, and may in fact distort the interpretation of the results of the experiment.

      The nocebo effect

      Before delving further into the lessebo effect, it is important to briefly understand what the nocebo effect is. “Nocebo” comes from Latin, which means “I must hurt”, unlike the term “placebo”, which means “I must please”. Knowledge of the nocebo effect is considered quite revealing about how everything about the placebo should be applied and interpreted (ineffective intervention) and its eponymous effect, because even what shouldn’t have an effect can hurt.

      As we have already mentioned, the placebo effect is, in essence, the improvement perceived by the participants in the control group even if they did not receive any product known to have an effect. The nocebo effect would be the opposite: it is the worsening of symptoms or signs of a state of health by waiting, conscious or not, of the undesirable effects of an intervention.

      In experimentation, there is always informed consent and, as we saw above, it is explained that the intervention can have both positive and negative effects. If the placebo effect consists in believing that the intervention is received and that the positive effects are obtained, in the case of the nocebo, it is also to believe that this intervention is received, but that its adverse effects are manifested. The participant has pessimistic expectations that lead them to believe that the treatment is harmful to them.

      What characterizes the lessebo effect?

      For a long time, investigations focused only on following up on the suggestions and expectations of the control group, both positive and negative. In the logic that in the experimental group something must necessarily happen, both a therapeutic effect and undesirable effects, this was not monitored with the effects of suggestion in this same group. Fortunately, although relatively recently, more attention has begun to be paid to how pessimistic expectations in the experimental group can negate the actual therapeutic effects of the intervention.

      If the placebo is the improvement seen in the control group and the nocebo worsening, the lessebo effect is the perception of less improvement, cancellation of effects or worsening in the experimental group. That is, the participants in the experimental group, those who are receiving treatment, believe that they received a placebo or are suffering from the side effects of the treatment, believing that their condition is getting worse.

      this this can be due to several causes. As with the nocebo effect, participants may have a pessimistic view of the effects of the experimental treatment, believing that they are more likely to experience its side effects than the therapeutic effects. Another thing that has been noticed is that there are not a few participants who, despite reading informed consent, do not understand it and think that “placebo” is synonymous with “harmful”. They believe that the experimental treatment is good and that the control is necessarily bad.

      scientific implications

      It’s clear that both the placebo effect and the nocebo affect research if they are not taken into account, but the effects of the placebo effect are even worse. As we have seen, the participant giving you an effective treatment may think that it is not or that it is a placebo, and suggests that it is not. ‘not improving or even getting worse.

      Dismissing something that, objectively speaking, works but which volunteers report as harmful because of their pessimistic expectations not only means rejecting a treatment that works, but also a waste of money and time. Whether it is a drug, a new psychological therapy or any other type of treatment, its design and application involve the mobilization of many efforts, and to be dismissed by the means of the experimental participants is a real mistake. .

      It is for this reason that on the basis of new research focused on the study of the lessebo effect the reliability of the participant must be taken into account, In the sense of what kind of expectations you have about the experience and whether it presents an unrealistic style of thinking. Whether you tend to be pessimistic or optimistic, you need to know this way of thinking and find out to what extent this participant is not going to skew the results of the experiment.

      Bibliographical references:

      • Mestre, TA (2020) Nocebo and lessebo effects. International Journal of Neurobiology 153, 121-146.
      • Mestre, TA, Shah, P., Marras, C., Tomlinson, G. and Lang, AE (2014). Another aspect of placebo: the lessebo effect in Parkinson’s disease: a meta-analysis. Neurology, 82 (16), 1402-1409. https://doi.org/10.1212/WNL.0000000000000340

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