Glossary
Here, we explain all of the terms used in alphabetical order, from adverse effects to unblinding, for you to refer to whenever you need.
All physical and psychological reactions to a drug or treatment that are not intended and which interfere with the desired effect. For more information, see the detailed text "What are adverse effects"?
Refers to all physical and neurobiological regulatory mechanisms relating to feelings and emotions such as sadness, fear and anger. The affective system also influences how we deal with stress. The autonomic nervous system is involved in this, as are hormones and neurotransmitters. The affective system is also called the emotion system. For more information on research projects involving the affective system, click here.
Noun: a pain-relieving drug that suppresses the sensation of pain without affecting consciousness and sensory perception. Adjective: relating to the stopping of pain.
Drugs from the class of psychotropic drugs. Primarily used to treat depression but can also be used for other mental disorders and for other symptoms such as pain. Studies have shown that the effect of antidepressants on mild to moderate depression is limited, and in some cases they do not lead to significantly greater improvement compared to a placebo. In the case of pain, certain antidepressants, the so-called tricyclic antidepressants or SSNRIs, do not act indirectly via the antidepressant effect, but rather via an activation of the body's own pain defence. The neurotransmitter norepinephrine plays a central role here.
Experimental or theoretical science that seeks to gain new insights or knowledge; concrete applications are initially of secondary importance. In general, basic research generates elementary knowledge for more advanced applied research. Basic medical research, for instance, seeks to lay the foundation for curing cancer, Alzheimer's disease, autoimmune diseases, depression or chronic pain. The Collaborative Research Centre Treatment Expectation aims to understand exactly which areas of the brain communicate in which way, or which signalling pathways are disturbed when people develop chronic pain or depression. Increasingly, this involves switching very quickly between experimental research (in the lab or on an animal model) and clinical research in order to test new approaches. This is what scientists call "translational research”.
Learning based on pairing a stimulus with a response. A famous example of classical conditioning is "Pavlov's dog": The dog was repeatedly presented with food together with a bell sound, to which he reacted with strong salivation. Over time, he salivated when he only heard the bell, without the presentation of food. In principle, classical conditioning works the same way in humans, e.g. taking a pain medication is associated with pain reduction.
Primarily refers to a drug or therapy study involving a large number of patients. In the case of new active substances, it is carried out following successful laboratory and safety studies. In addition to efficacy and dose finding, the focus is now also on probable and possible side effects. Please also read the detailed ethical requirements under which clinical trials are conducted.
Since study participants do not usually know whether they will be treated in the study arm with the active substance or in the placebo arm, this type of clinical trial is described as "blinded." Moreover, because the expectations of physicians or investigators can also have an influence, in many studies, they are also unaware of the treatment group to which patients or study participants have been allocated. These studies are called "double-blind". The allocation to the treatment arms is randomized (by chance).
Messenger substance (neurotransmitter) of the central nervous system that controls, for example, motivation and drive. Dopamine acts in the brain's reward centre, where it presumably also influences pain perception, among other things.
A study in which neither the study participants nor the investigators know who is receiving the substance being tested (e.g., a new drug) and who is receiving a placebo (i.e., an inactive tablet). Typically used in clinical trials of drug efficacy. The purpose of a double-blind study is to prevent investigators from passing on certain negative or positive expectations to participants and vice versa, therefore minimising the influence of expectations on the results of the study. This is important in the drug development and testing phase, in which the basic efficacy of a new substance or procedure is investigated. More information can be found here.
A study controlled throughout by the research leaders in order to test an "if-then" hypothesis. For example, an active substance that has already been adequately tested might be administered in an experimental study to test how it affects perception or behaviour in specific tasks. This can be implemented either in a between-subjects design (separate experimental group with active substance and control group without active substance) or in a within-subjects design (all participants receive the active substance in one session and do not receive it in a second, separate session). At the end, the effects in the two conditions (with and without active substance) are measured and compared. The investigators systematically vary influencing factors, i.e. mechanisms such as attention, learning processes, anxiety, expectations and such like, as well as the general conditions, and then examine how this affects behaviour or brain activity. Studies that test the efficacy, mode of action, or adverse effects of drugs are called "clinical trials." More information can be found in this text.
fMRI distinguishes active areas of the human brain from inactive ones. An increased blood flow to brain regions is used as an indicator of brain activity, i.e. of greater "use" of this region. This makes it possible to observe which areas of the brain react more to certain stimuli than others. This type of imaging can also clarify whereabouts in the brain the placebo effect is occurring.
Term used to describe treatments that are widely accepted to be the best and in accordance with the guidelines in their respective fields and that have the best risk-benefit ratio. These can be tried-and-tested procedures or new ones that revolutionize a treatment.
A heightened sensitivity to pain. In people with hyperalgesia, the pain receptors in the nervous system are hypersensitive, for example due to endogenous substances that are released by the tissue during inflammation. The pain threshold drops and pain stimuli such as pressure, heat or cold trigger stronger pain signals than usual.
Examination techniques that provide layer-by-layer image data of organs or tissue structures. In medical diagnostics, computed tomography (CT), magnetic resonance imaging (MRI) or positron emission tomography (PET) are mainly used. In neuroscientific research, so-called functional magnetic resonance imaging (fMRI) allows researchers to see not only structural images of tissue but even the activity of brain areas in specific situations. In other words, you can "watch the brain at work." For more information on research projects that use this technique to better understand pain control, for example, see Project A02 and Project A01.
Biochemical substances that transport information in the nervous system, pass it on to other cells, and consequently stimulate numerous functions.
Biochemical substances that transport information in the nervous system, pass it on to other cells, and consequently stimulate numerous functions.
Translated from the original Latin, the term means "I will harm." An inactive substance that promotes negative expectations, leading to symptoms such as adverse effects. Unlike the placebo effect, the nocebo effect does not involve a sham medication, which would have overtly harmful effects. Many specific explanations can be found here. The nocebo effect is the opposite of the placebo effect. In its original meaning, the term refers to a worsening of well-being following the administration of a sham medication. In a broader sense, however, it encompasses the effects of negative expectations about a drug or treatment, such as the expectation of pain or doubts about the efficacy of a treatment. The nocebo effect can be measured neurobiologically but it varies from individual to individual, depending on factors such as symptoms, state of disease, treatment, and personality factors. Studies within the Collaborative Research Centre Treatment Expectation are also investigating the nocebo effect in Project A10 and Project A15.
In our explanatory movie, we describe the effect of a potent pain medication in patients with positive, neutral, and negative expectation, powerfully illustrating the nocebo effect.
In contrast to clinical trials, in which patients do not know whether they are receiving the placebo or the real treatment, patients treated with open-label placebos (OLP) are informed about the nature of the placebo treatment, and they also know that they are being treated with placebos. Amazingly, several independent studies examining various different diseases have demonstrated that OLP treatment can have a positive impact on, for example, pain perception, physical functioning, and quality of life. There are also encouraging findings regarding other illnesses such as depression or chronic fatigue syndrome. Therefore, intensive research is currently being conducted into how OLPs work, which patients are especially likely to benefit from them, and how they might be used in clinical routine.
Collective term for natural substances found in the opium poppy or artificially produced substances known primarily for their pain-reducing properties. Opioids specifically inhibit the transmission of pain, especially in the brain and spinal cord. The best-known opioid is morphine.
All parts of the nervous system that are involved in the development of pain. This includes components in the peripheral nervous system (receptors and fibres for pain perception), spinal cord, brainstem, and various areas of the brain (thalamus, hypothalamus, limbic system, and neocortex). This interaction results in a variety of different and individual perceptions of pain.
Translated from the original Latin, the term means "I will please." Placebo refers to a medicine without an active ingredient, or a sham treatment that feels "real." Placebos are primarily used in clinical trials to test the efficacy of new drugs. Research is currently being conducted into how placebos can be used in a targeted way within treatments, for instance to improve the effect of real medications.
A positive physical or psychological change after taking a medication without any active substance (placebos) or after a sham treatment such as a simulated operation or an infusion with a simple saline solution. But the placebo effect also plays a role in conventionally prescribed treatments, such as those with pharmacological effects. The placebo effect can be measured neurobiologically but varies from individual to individual and depends on various factors.
This describes all improvements observed in the placebo arm of a randomized controlled trial. It is composed of the natural course of the disease and the response triggered by the patient him/herself (placebo effect).
Study participants are randomly (by chance) assigned to different test groups, e.g., who gets the real drug and who gets the placebo. This should ensure that personal factors (such as age, gender, education, etc.) are evenly distributed across the groups and can be ruled out as additional influences on the study outcomes. Randomized placebo-controlled double-blind trials are seen as the silver bullet for achieving unbiased results from clinical trials.
System of nerve cells in the brain in which positive feelings are generated with the help of the neurotransmitter dopamine. The mesolimbic system promotes certain patterns of behaviour associated with reward.
A prediction that comes true when we expect a certain outcome. In this way, we ourselves contribute to our expectation being fulfilled. For example, if patients are pessimistic about a new treatment, it won’t work as well.
Any effects that occur in addition to the desired effect of a drug or treatment. For medications, all known unwanted, undesirable side effects must be listed in the package insert, even if they have only previously occurred in very rare cases. In the case of medical treatment, the doctor must point this out to the patient, unless the patient releases the doctor from this duty of information. Whether and to what extent undesired effects occur with a treatment depends not least on the patient's expectations. Patients who expect pain are more likely to experience it. Please also read the text "What are adverse effects"?
Study in which only the study participants are not told which substance they have received (the real drug or the placebo). The investigators, on the other hand, are aware of which participants received which substance.
A thing or event that elicits a response, e.g., a white doctor's coat leading to a rise in blood pressure (so-called white coat syndrome).
Positive or negative expectations of treatments (drugs, therapies, etc.) based on previous experiences or generated by information from, e.g. the doctor, the media, or by observing other patients. All of these factors can influence the outcome of a treatment. Has a similar treatment helped in the past? Or is it mainly the side effects that are remembered?
Treatment expectations are also shaped by how the treatment provider communicates. Empathic and positive communication promotes positive expectations and therefore successful treatment.
Expectations are not only the driving force of placebo effects, but also influence active treatments e.g. drug treatments – positively or negatively. For more information, click here.
Unblinding occurs when either the investigators or participants find out which substance was administered during a double-blind or single-blind trial and communicates this to the respective other party. This can happen, for example, because severe side effects occur, leading participants to guess that they have been given the real drug (see the above link to clinical trials). In many studies, however, it is also planned from the outset that at the end of the study, all participants will find out which group they were in.