Effects of overshadowing on conditioned nausea in cancer patients: an experimental study

D2 Receptors and Sodium Ion Channel Blockades of the Basolateral Amygdala Attenuate Lithium Chloride-Induced Conditioned Taste Aversion Applying to Cancer Chemotherapy Nausea and Vomiting

Cancer patients regularly suffer from the behavioral symptoms of chemotherapy-induced nausea and vomiting. Particularly, it is involved in Pavlovian conditioning. Lithium chloride (LiCl) was used as the unconditioned stimulus (US) and contingent with the tastant, for example, a saccharin solution (i.e., the conditioned stimulus; CS), resulted in conditioned taste aversion (CTA) to the CS intake. The present study employed an animal model of LiCl-induced CTA to imitate chemotherapy-induced nausea and vomiting symptoms. Recently, the basolateral amygdala (BLA) was shown to mediate LiCl-induced CTA learning; however, which brain mechanisms of the BLA regulate CTA by LiCl remain unknown. The present study was designed to test this issue, and 4% lidocaine or D2 blocker haloperidol were microinjected into BLA between the 0.1% saccharin solution intake and 0.15M LiCl. The results showed lidocaine microinjections into the BLA could attenuate the LiCl-induced CTA. Microinjections of haloperidol blunted the CTA learning by LiCl. Altogether, BLA via the sodium chloride ion channel and D2 receptors control LiCl-induced conditioned saccharin solution intake suppression. The findings can provide some implications and contributions to cancer chemotherapy-induced nausea and vomiting side effects, and will help to develop novel strategies to prevent the side effects of cancer chemotherapy.

Behavioral factors to modulate immunotherapy efficacy in cancer

Immune checkpoint inhibitors, including anti-PD-1 and anti-CTLA-4 therapies, are used to (re)activate the immune system to treat cancer. Despite promising results, a large group of patients does not respond to checkpoint inhibition. In the vulnerability-stress model of behavioral medicine, behavioral factors, such as stress, exercise and classical pharmacological conditioning, predict cancer incidence, recurrence and the efficacy of conventional cancer treatments. Given the important role of the immune system in these processes, certain behavior may be promising to complement immune checkpoint inhibition therapy. Here, we discuss the preliminary evidence and suitability of three behavioral mechanisms, i.e. stress modulation, exercise and classical pharmacological conditioning for the benefit of immunotherapy. It is crucial to study the potential beneficial effects of behavioral strategies that support immunotherapeutic anti-tumor effects with rigorous experimental evidence, to exploit behavioral mechanisms in improving checkpoint inhibition efficacy.

Pre-Exposure, But Not Overshadowing, Inhibits Nocebo Hyperalgesia

Nocebo hyperalgesia is a pervasive problem that significantly adds to the burden of pain. Conditioning is a key mechanism of nocebo hyperalgesia and recent evidence indicates that, once established, nocebo hyperalgesia is resistant to extinction. This means that preventive strategies are critical. We therefore tested whether two novel strategies - overshadowing (Experiment 1) and pre-exposure (Experiment 2) - could inhibit conditioned nocebo hyperalgesia. Overshadowing involves introducing additional cues during conditioning that should compete with and overshadow learning about the target nocebo cue. Pre-exposure involves pre-exposing the target nocebo cue in the absence of pain, which should diminish its ability to become associated with pain later. In both studies, healthy volunteers (N = 141) received exposure to a series of electrocutaneous pain stimuli with and without a sham electrode 'activated', which they were led to believe was a genuine hyperalgesic treatment. Nocebo conditioning was achieved by pairing sham activation with high pain prior to testing at equivalent pain intensity. In both studies, standard nocebo conditioning led to clear nocebo hyperalgesia relative to natural history controls. In Experiment 1, there was no evidence that overshadowing attenuated nocebo hyperalgesia. Importantly, however, Experiment 2 found that pre-exposure successfully attenuated nocebo hyperalgesia with post hoc analysis suggesting that this effect was dose-dependent. These findings provide novel evidence that pre-exposure, but not overshadowing, could be a cheap and effective way for mitigating the substantial harm caused by conditioned nocebo hyperalgesia in clinical settings. PERSPECTIVE: Nocebo hyperalgesia causes substantial patient burden with few preventive options available. Our study found novel evidence that pre-exposing treatment cues without pain, but not overshadowing them with other cues, has the capacity to inhibit conditioned nocebo hyperalgesia. Pre-exposure may therefore be an effective preventive strategy to combat nocebo hyperalgesia.

Placebo and Nocebo Effects Across Symptoms: From Pain to Fatigue, Dyspnea, Nausea, and Itch

Placebo and nocebo effects are, respectively, the helpful and harmful treatment effects that do not arise from active treatment components. These effects have thus far been researched most often in pain. It is not yet clear to what extent these findings from pain can be generalized to other somatic symptoms. This review investigates placebo and nocebo effects in four other highly prevalent symptoms: dyspnea, fatigue, nausea, and itch. The role of learning mechanisms (verbal suggestions, conditioning) in placebo and nocebo effects on various outcomes (self-reported, behavioral, and physiological) of these different somatic symptoms is explored. A search of experimental studies indicated that, as in pain, the combination of verbal suggestion and conditioning is generally more effective than suggestion alone for evoking placebo and nocebo effects. However, conditioning appears more and verbal suggestions less relevant in symptoms other than pain, with the exception of placebo effects on fatigue and nocebo effects on itch. Physiological measures, such as heart rate, lung function, or gastric activity, are rarely affected even when self-reported symptoms are. Neurobiological correlates are rarely investigated, and few commonalities appear across symptoms. Expectations generally predict placebo and nocebo effects for dyspnea and itch but seem less involved in fatigue and nausea. Individual characteristics do not consistently predict placebo or nocebo effects across symptoms or studies. In sum, many conclusions deriving from placebo and nocebo pain studies do appear to apply to other somatic symptoms, but a number of important differences exist. Understanding what type of learning mechanisms for which symptom are most likely to trigger placebo and nocebo effects is crucial for generalizing knowledge for research and therapies across symptoms and can help clinicians to optimize placebo effects in practice.

Does Sex/Gender Play a Role in Placebo and Nocebo Effects? Conflicting Evidence From Clinical Trials and Experimental Studies

Sex has been speculated to be a predictor of the placebo and nocebo effect for many years, but whether this holds true or not has rarely been investigated. We utilized a placebo literature database on various aspects of the genuine placebo/nocebo response. In 2015, we had extracted 75 systematic reviews, meta-analyses, and meta-regressions performed in major medical areas (neurology, psychiatry, internal medicine). These meta-analyses were screened for whether sex/gender differences had been noted to contribute to the placebo/nocebo effect: in only 3 such analyses female sex was associated with a higher placebo effect, indicating poor evidence for a contribution of sex to it in RCTs. This was updated with another set of meta-analyses for the current review, but did not change the overall conclusion. The same holds true for 18 meta-analyses investigating adverse event (nocebo) reporting in RCT in the placebo arm of trials. We also screened our database for papers referring to sex/gender and the placebo effect in experimental studies, and identified 28 papers reporting 29 experiments. Their results can be summarized as follows: (a) Despite higher sensitivity of pain in females, placebo analgesia is easier to elicit in males; (b) It appears that conditioning is effective specifically eliciting nocebo effects; (c) Conditioning works specifically well to elicit placebo and nocebo effects in females and with nausea; (d) Verbal suggestions are not sufficient to induce analgesia in women, but work in men. These results will be discussed with respect to the question why nausea and pain may be prone to be responsive to sex/gender differences, while other symptoms are less. Lastly, we will discuss the apparent discrepancy between RCT with low relevance of sex, and higher relevance of sex in specific experimental settings. We argue that the placebo response is predominantly the result of a conditioning (learning) response in females, while in males it predominantly may be generated via (verbal) manipulating of expectancies. In RCT therefore, the net outcome of the intervention may be the same despite different mechanisms generating the placebo effect between the sexes, while in experimental work when both pathways are separated and explicitly explored, such differences may surface.

Conditioned hormonal responses: A systematic review in animals and humans

In contrast to classical conditioning of physiological responses such as immune responses and drug effects, only a limited number of studies investigated classical conditioning of endocrine responses. The present paper is the first systematic review that integrates evidence from animal and human trials regarding the possibility to condition the endocrine responses. Twenty-six animal and eight human studies were included in the review. We demonstrated that there is accumulating evidence that classical conditioning processes are able to influence specific endocrine responses, such as cortocosterone/cortisol and insulin, while more limited evidence exists for other hormones. Animal and human studies were generally consistent in their findings; however, the limited number of human studies makes it difficult to generalize and translate the results of animal research to humans. Next to methodological recommendations for future studies, we suggest several ways how classically conditioned endocrine responses can be used in clinical practice.

Nocebo Effects and Experimental Models in Visceral Pain

Despite its clinical relevance and the potential to extend insights into the processing and modulation of pain derived from investigations of placebo phenomena, the nocebo effect has received comparably little attention over the past decades. Research from experimental and clinical studies is only beginning to unravel the behavioral, functional, and psychoneurobiological mechanisms underlying the nocebo effect. Herein, we summarize current evidence regarding nocebo effects in the field of pain, with a particular emphasis on visceral pain. We provide an overview over behavioral and neuroimaging findings on the impact of expectations and learning and propose promising future directions to help fostering the transition of experimental research from bench to bedside.

Different Disclosed Probabilities to Receive an Antiemetic Equally Decrease Subjective Symptoms in an Experimental Placebo Study: To Be or Not to Be Sure

PURPOSE

The purpose of this study was to examine whether the disclosed probability of receiving an antiemetic affects nausea.

METHODS

Forty-eight healthy participants (mean [SD] age, 26.8 [5.4] years; 50% female) were exposed to 5 × 2 minutes of nauseogenic body rotations on 2 days. On day 2, participants were randomized to 3 experimental groups that were given different instructions concerning the probability of receiving an antiemetic remedy (100%, 50%, or 0% probability), whereas all received an inert substance. Subjective symptoms, behavioral (rotation tolerance) measures, and physiologic (electrogastrogram) measures of nausea were assessed and mediator and moderator analyses performed for effects of expectations and psychological characteristics on outcomes.

FINDINGS

Disclosed probabilities of both 100% and 50% significantly reduced subjective symptoms of nausea in an equal manner compared with the 0% probability group from day 1 to day 2. This effect was found for neither rotation tolerance nor myoelectric gastric activity. Expectations and psychological characteristics did not affect the results found. Post hoc analyses revealed that women only seem to be susceptible to this placebo effect.

IMPLICATIONS

Nausea is susceptible to placebo effects independent of the disclosed probability of receiving a drug and of explicit expectations. In line with placebo research, this effect is probably attributable to central mechanisms, and it is speculated that it could be related to the reward circuitry and social interactions.

2016 updated MASCC/ESMO consensus recommendations: Anticipatory nausea and vomiting in children and adults receiving chemotherapy

PURPOSE

We aimed to update the 2011 recommendations for the prevention and treatment of anticipatory nausea and vomiting in children and adults receiving chemotherapy.

METHODS

The original systematic literature search was updated. Randomized studies were included in the evidence to support this guideline if they as follows: were primary studies published in a journal in full text (i.e., abstracts, letters, book chapters, and dissertations were excluded); published in English; evaluated an intervention for the prevention or treatment of anticipatory nausea and vomiting; reported the proportion of patients experiencing complete control of anticipatory nausea and vomiting consistently and; included at least ten participants per study arm for comparative studies and at least ten participants overall for noncomparative studies.

RESULTS

Eighty-eight new citations were identified. Of these, nine were brought to full-text screening; none met inclusion criteria. The guideline panel continues to recommend that anticipatory nausea and vomiting are best prevented through optimization of acute and delayed phase chemotherapy-induced nausea and vomiting control. Benzodiazepines and behavioral therapies, in particular progressive muscle relaxation training, systematic desensitization and hypnosis, continue to be recommended for the treatment of anticipatory nausea and vomiting.

CONCLUSIONS

No new information regarding interventions aimed at treating or preventing ANV that met criteria for inclusion in this systematic review was identified. The 2015 MASCC recommendations affirm the content of the 2009 MASCC recommendations for the prevention and treatment of anticipatory nausea and vomiting.

Overshadowing and latent inhibition in nausea-based context conditioning in humans: Theoretical and practical implications

Volunteer participants underwent nausea-inducing body rotation in a distinctive context, and the acquired ability of the contextual cues to evoke nausea was subsequently assessed by a symptom rating scale. One group received prior exposure to the context (a latent inhibition procedure); a second consumed a novel flavour prior to rotation (an overshadowing procedure); a third group experienced both procedures; and a control group received neither. When tested in the context in the absence of rotation, all groups reported an increase in nausea-related symptoms at the time when rotation had previously occurred, an outcome consistent with the occurrence of conditioned nausea. The magnitude of this increase did not differ across the groups, but the overall level of responsiveness (the degree to which nausea-related symptoms were reported) was enhanced in the latent inhibition and reduced in the overshadowing condition. Cortisol levels showed the same pattern. The implications of these findings for the proposal that overshadowing and latent inhibition procedures might be used to control the development of anticipatory nausea in patients undergoing chemotherapy is considered.

Neuro-Bio-Behavioral Mechanisms of Placebo and Nocebo Responses: Implications for Clinical Trials and Clinical Practice

The placebo effect has often been considered a nuisance in basic and particularly clinical research. This view has gradually changed in recent years due to deeper insight into the neuro-bio-behavioral mechanisms steering both the placebo and nocebo responses, the evil twin of placebo. For the neuroscientist, placebo and nocebo responses have evolved as indispensable tools to understand brain mechanisms that link cognitive and emotional factors with symptom perception as well as peripheral physiologic systems and end organ functioning. For the clinical investigator, better understanding of the mechanisms driving placebo and nocebo responses allow the control of these responses and thereby help to more precisely define the efficacy of a specific pharmacological intervention. Finally, in the clinical context, the systematic exploitation of these mechanisms will help to maximize placebo responses and minimize nocebo responses for the patient's benefit. In this review, we summarize and critically examine the neuro-bio-behavioral mechanisms underlying placebo and nocebo responses that are currently known in terms of different diseases and physiologic systems. We subsequently elaborate on the consequences of this knowledge for pharmacological treatments of patients and the implications for pharmacological research, the training of healthcare professionals, and for the health care system and future research strategies on placebo and nocebo responses.

Placebo effects and their determinants in gastrointestinal disorders

Placebo effects in clinical trials have sparked an interest in the placebo phenomenon, both in randomized controlled trials (RCTs) and in experimental gastroenterology. RCTs have demonstrated similar short-term and long-term placebo response rates in gastrointestinal compared to other medical diagnoses. Most mediators and moderators of placebo effects in gastrointestinal diseases are also of similar type and size to other medical diagnoses and not specific for gastrointestinal diagnoses. Other characteristics such as an increase in the placebo response over time and the placebo-enhancing effects of unbalanced randomization were not seen, at least in IBS. Experimental placebo and nocebo studies underscore the 'power' of expectancies and conditioning processes in shaping gastrointestinal symptoms not only at the level of self-reports, but also within the brain and along the brain-gut axis. Brain imaging studies have redressed earlier criticism that placebo effects might merely reflect a response bias. These findings raise hope that sophisticated trials and experiments designed to boost positive expectations and minimize negative expectations could pave the way for a practical and ethically sound use of placebo knowledge in daily practice. Rather than focusing on a 'personalized' choice of drugs based on biomarkers or genes, it might be the doctor-patient communication that needs to be tailored.

Cooperation came first: evolution and human cognition

Contextual behavioral perspectives on learning and behavior reside under the umbrella of evolution science. In this paper we briefly review current developments in evolution science that bear on learning and behavior, concluding that behavior is now moving to the center of evolution studies. Learning is one of the main ladders of evolution by establishing functional benchmarks within which genetic adaptations can be advantaged. We apply that approach to the beginning feature of human cognition according to Relational Frame Theory: derived symmetry in coordination framing. When combined with the idea that cooperation came before major advances in human cognition or culture, existing abilities in social referencing, joint attention, perspective-taking skills, and relational learning ensure that the behavioral subcomponents of symmetrical equivalence relations would be reinforced. When coordination framing emerged and came under arbitrary contextual control as an operant class, a template was established for the development of multiple relational frames and the emergence and evolutionary impact of human cognition as we know it. Implications of these ideas for translational research are briefly discussed.

Serial overshadowing of taste aversion learning by stimuli preceding the target taste

Three experiments tested whether events taking place before a rat has access to a target taste, sucrose, can proactively interfere with the acquisition of a sucrose aversion when sucrose is followed by a lithium chloride injection. Using a serial overshadowing procedure with various delays before lithium injection, proactive interference by a taste (Experiments 1 and 3) and by a novel context (Experiment 2) was found following two conditioning sessions, but not after a single conditioning session. Conversely, overshadowing by a taste given after the target was detectable after a single conditioning trial (Experiment 3) and, thus, indicated that retroactive interference involves a process different from that producing proactive interference. A simulation confirmed that the results are consistent with a modified Rescorla and Wagner (1972) interpretation of Revusky's (1971) concurrent interference theory of delay learning.

Anticipatory nausea and vomiting due to chemotherapy

As a specific variation of chemotherapy-induced nausea and vomiting, anticipatory nausea and vomiting (ANV) appears particularly linked to psychological processes. The three predominant factors related to ANV are classical conditioning; demographic and treatment-related factors; and anxiety or negative expectancies. Laboratory models have provided some support for these underlying mechanisms for ANV. ANV may be treated with medical or pharmacological interventions, including benzodiazepines and other psychotropic medications. However, behavioral treatments, including systematic desensitization, remain first line options for addressing ANV. Some complementary treatment approaches have shown promise in reducing ANV symptoms. Additional research into these approaches is needed. This review will address the underlying models of ANV and provide a discussion of these various treatment options.

Individual differences in chemotherapy-induced anticipatory nausea

Anticipatory Nausea (AN) is a severe side effect of chemotherapy that can lead cancer patients to discontinue their treatment. This kind of nausea is usually elicited by the re-exposure of the patients to the clinical context they need to attend to be treated. There has been considerable agreement that AN represents a paradigmatic example of Pavlovian conditioning, and within this framework, several behavioral interventions have been proposed in order to prevent this phenomenon. However, some studies have questioned the validity of the Pavlovian approach, suggesting that CS-US associations are neither necessary nor sufficient for AN to occur. The data and the alternative theories behind such criticisms are discussed. Additionally, it is suggested that animal models of AN could be enriched by taking into account rats' individual differences.

Reduction of motion sickness with an enhanced placebo instruction: an experimental study with healthy participants

OBJECTIVE

Expectancy and conditioning are underlying mechanisms of placebo and nocebo responses. In previous studies with motion sickness, we could induce nocebo responses by both methods, but no placebo responses.

METHODS

In Experiment 1, 64 volunteers (50% women, mean age = 23.5 years) were evaluated to determine the degree they realized speed changes in nauseogenic rotation. For Experiment 2, 32 volunteers (50% women, mean age = 26.0 years) were exposed to fast rotation (15 rounds per minute, or rpm) on Day 1. On Day 2, they either received a drink with a presumed effective antiemetic (actually placebo) or were told they belonged to the control group. Rotation was surreptitiously reduced (to 10 rpm). On Day 3, they were tested with the initial rotation speed. Outcome variables in both experiments were symptom ratings; additionally in Experiment 2, the number of nauseogenic head movements, tolerated rotation time, and electrogastrogram were analyzed for changes between Days 1 and 2 (expectancy plus speed reduction) and Days 1 and 3 (expectancy plus conditioning).

RESULTS

In Experiment 1, a dose-response function was established for different rotation speeds, with the smallest perceived difference between 10 and 15 rpm. In Experiment 2, placebo application induced better maximal symptom rating, head movement, and rotation time at Day 2 (F = 3.097, p = .043) and Day 3 (F = 3.401, p = .031). Electrogastrogram was unaffected.

CONCLUSIONS

Verbal suggestions combined with a conditioning procedure are effective in reducing symptoms of motion sickness.

Overshadowing as prevention of anticipatory nausea and vomiting in pediatric cancer patients: study protocol for a randomized controlled trial

BACKGROUND

Emesis and nausea are side effects induced by chemotherapy. These effects lead to enormous stress and strain on cancer patients. Further consequences may include restrictions in quality of life, cachexia or therapy avoidance. Evidence suggests that cancer patients develop the side effects of nausea and vomiting in anticipation of chemotherapy. Contextual cues such as smell, sounds or even the sight of the clinic may evoke anticipatory nausea and vomiting prior to infusion. Anticipatory nausea and vomiting are problems that cannot be solved by administration of antiemetica alone.The purpose of the proposed randomized placebo-controlled trial is to use an overshadowing technique to prevent anticipatory nausea and vomiting and to decrease the intensity and duration of post-treatment nausea and vomiting. Furthermore, the effect on anxiety, adherence and quality of life will be evaluated.

METHODS/DESIGN

Fifty-two pediatric cancer patients will be evenly assigned to two groups: an experimental group and a control group. The participants, hospital staff and data analysts will be kept blinded towards group allocation. The experimental group will receive during three chemotherapy cycles a salient piece of candy prior to every infusion, whereas the control group will receive flavorless placebo tablets.

DISCUSSION

If an effectiveness of the overshadowing technique is proven, implementation of this treatment into the hospitals' daily routine will follow. The use of this efficient and economic procedure should aid a reduced need for antiemetics.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN30242271/

Effects of ginger and expectations on symptoms of nausea in a balanced placebo design

OBJECTIVE

Ginger effects on (experimental) nausea have been described, but also strong placebo effects and sex differences when nausea is involved. The "balanced placebo design" has been proposed to allow better separation of drug and placebo effects.

METHODS

Sixty-four healthy participants (32 women) were randomly assigned to receive an antiemetic ginger preparation or placebo, and half of each group was told to have received drug or placebo. They were exposed to 5×2 min body rotations to induce nausea. Subjective symptoms and behavioral (rotation tolerance, head movements) and physiological measures (electrogastrogram, cortisol) were recorded. Groups were balanced for sex of participants and experimenters.

RESULTS

Ginger and the information given did not affect any outcome measure, and previous sex differences could not be confirmed. Adding the experimenters revealed a significant four-factorial interaction on behavioral but not on subjective or physiological measures Men who received placebo responded to placebo information when provided by the male experimenter, and to ginger information when provided by the female experimenter. This effect was not significant in women.

CONCLUSION

The effects of an antiemetic drug and provided information interact with psychosocial variables of participants and experimenters in reports of nausea.

The nocebo effect and its relevance for clinical practice

Negative expectations deriving from the clinical encounter can produce negative outcomes, known as nocebo effects. Specifically, research on the nocebo effect indicates that information disclosure about potential side effects can itself contribute to producing adverse effects. Neurobiological processes play a role in the nocebo effect, and this article provides a selective review of mechanistic research on the nocebo effect. Comparatively little attention has been directed to clinical studies and their implications for daily clinical practice. The nocebo response is influenced by the content and the way information is presented to patients in clinical trials in both the placebo and active treatment conditions. Nocebo effects adversely influence quality of life and therapy adherence, emphasizing the need for minimizing these responses to the extent possible. Evidence further indicates that the informed consent process in clinical trials may induce nocebo effects. This article concludes with ethical directions for future patient-oriented research and routine practice.

Treatment of Nausea and Vomiting During Chemotherapy

Nausea and vomiting are two of the most troubling side effects patients experience during chemotherapy. While newly available treatments have improved our ability to manage nausea and vomiting, anticipatory and delayed nausea and vomiting are still a major problem for patients receiving chemotherapy. Many cancer patients will delay or refuse future chemotherapy treatments and contemplate stopping chemotherapy altogether because of their fear of experiencing further nausea and vomiting. The purpose of this article is to provide an overview of the patho-psychophysiology of chemotherapy-induced nausea and vomiting and the recommended guidelines for treatment.

Anticipatory nausea and vomiting

A commonly reported consequence of post-treatment nausea or vomiting is the development of anticipatory nausea and vomiting (ANV). In most published work, nausea is reported to occur before chemotherapy drugs are administered by approximately 20% of patients at any one chemotherapy cycle and by 25-30% of patients by their fourth chemotherapy cycle. Most studies in adult patients strongly support the view that the development of ANV involves elements of classical conditioning. The best method to avoid development of ANV is to adequately prevent both vomiting and nausea from the first exposure to chemotherapy. If anticipatory side effects develop, behavioral treatment techniques, such as systematic desensitization, have been shown effective. Benzodiazepines used in combination with behavioral techniques or antiemetics may also be useful. The evidence on which these conclusions are based is reviewed in this article.

Psychological burden of food allergy

One fifth of the population report adverse reactions to food. Reasons for these symptoms are heterogeneous, varying from food allergy, food intolerance, irritable bowel syndrome to somatoform or other mental disorders. Literature reveals a large discrepancy between truly diagnosed food allergy and reports of food allergy symptoms by care seekers. In most studies currently available the characterization of patient groups is incomplete, because they did not distinguish between immunologic reactions and other kinds of food reactions. In analysing these adverse reactions, a thorough physical and psychological diagnostic approach is important. In our qualitative review, we present those diagnostic measures that are evidenced-based as well as clinically useful, and discuss the various psychological dimensions of adverse reactions to food. It is important to acknowledge the complex interplay between body and mind: Adults and children suffering from food allergy show impaired quality of life and a higher level of stress and anxiety. Pavlovian conditioning of adverse reactions plays an important role in maintaining symptoms. The role of personality, mood, or anxiety in food reactions is debatable. Somatoform disorders ought to be identified early to avoid lengthy and frustrating investigations. A future task will be to improve diagnostic algorithms, to describe psychological aspects in clearly characterised patient subgroups, and to develop strategies for an optimized management of the various types of adverse reactions to food.

Role of classical conditioning in learning gastrointestinal symptoms

Nausea and/or vomiting are aversive gastrointestinal (GI) symptoms. Nausea and vomiting manifest unconditionally after a nauseogenic experience. However, there is correlative, quasiexperimental and experimental evidence that nausea and vomiting can also be learned via classical (Pavlovian) conditioning and might occur in anticipation of the nauseogenic event. Classical conditioning of nausea can develop with chemotherapy in cancer patients. Initially, nausea and vomiting occur during and after the administration of cytotoxic drugs (post-treatment nausea and vomiting) as unconditioned responses (UR). In addition, 20%-30% of cancer patients receiving chemotherapy report these side effects, despite antiemetic medication, when being re-exposed to the stimuli that usually signal the chemotherapy session and its drug infusion. These symptoms are called anticipatory nausea (AN) and/or anticipatory vomiting (ANV) and are explained by classical conditioning. Moreover, there is recent evidence for the assumption that post-chemotherapy nausea is at least partly influenced by learning. After summarizing the relevant assumptions of the conditioning model, revealing that a context can become a conditioned stimulus (CS), the present paper summarizes data that nausea and/or vomiting is acquired by classical conditioning and, consequently, may be alleviated by conditioning techniques. Our own research has focussed on two aspects and is emphasized here. First, a conditioned nausea model was established in healthy humans using body rotation as the nausea-inducing treatment. The validity of this motion-sickness model to examine conditioning mechanisms in the acquisition and alleviation of conditioned nausea and associated endocrine and immunological responses is summarized. Results from the rotation-induced motion sickness model showed that gender is an important moderator variable to be considered in further studies. This paper concludes with a review of the application of the demonstrated conditioning principles as interventions to ameliorate distressing AN/ANV in cancer patients undergoing chemotherapy, which is the second focus of our work.

The psyche and the gut

Research on gut-brain interactions has increased over the last decade and has brought about a number of new topics beyond "classical" subjects, such as "stress" and "personality", which have dominated the psychosomatic literature on gastrointestinal disorders over the past century. These novel topics include brain imaging of intestinal functions, placebo responses in gastroenterology, learning of gastrointestinal symptoms, quality of life in patients with intestinal complaints, and psychotherapy and familial aggregation of functional intestinal disorders. Currently, these new topics appear with a frequency of 1% to 3% in leading gastroenterological journals, either as data presentation or review papers. Increasing focus underlines the importance of enhancing our understanding on how the psyche and the brain communicate in order to better meet the needs of our patients.

Anticipatory Nausea: The Role of Individual Differences Related to Sensory Perception and Autonomic Reactivity

BACKGROUND

Anticipatory nausea (AN) during chemotherapy has been difficult to control with conventional antiemetics. AN can lead cancer patients to delay or discontinue chemotherapy, possibly compromising the treatment.

PURPOSE

The aim is to investigate the possible influence on the development of AN of individual differences in absorption, somato-sensory amplification, and autonomic perception-measures theorized to be related to sensory perception and autonomic reactivity.

METHODS

Prior to treatment, 125 women (M age = 48.5 years) undergoing adjuvant chemotherapy for breast cancer rated their expected severity of side effects and completed the Tellegen Absorption Scale, the Somato-Sensory Amplification Scale, and the Autonomic Perception Questionnaire. AN, as well as anticipatory vomiting (AV), distress, and worry/anxiety, were measured prior to the fourth, sixth, and last cycle of chemotherapy. Posttreatment nausea (PN), vomiting, and fatigue were measured after the first, fourth, sixth, and last cycle.

RESULTS

34% of the women reported AN before 1 or more cycles. When controlling for treatment characteristics and other known predictors, AN was significantly associated with high absorption in addition to severity of PN, pretreatment worry/anxiety, and not receiving radiotherapy between chemotherapy sessions. AV was not associated with any of the variables investigated. Our data suggest that the association is strongest in the early phases of treatment.

CONCLUSIONS

Our results partly confirm the results of a previous study showing absorption and autonomic perception as predictors of anticipatory side effects in cancer patients receiving chemotherapy. Individuals high in absorption may be more autonomically reactive to aversive stimuli and, subsequently, more conditionable. Additional radiotherapy could be a competing stimulus, reducing the conditioning of chemotherapy-related nausea. Further studies investigating possible psycho-physiological mechanisms in the development of AN are needed.

Pavlovian conditioning of nausea and vomiting

Cancer patients undergoing cytotoxic drug treatment often experience side-effects, the most distressing being nausea and vomiting. Despite antiemetic drugs, 25-30% of the chemotherapy patients report these side-effects when being re-exposed to the stimuli that usually signal the chemotherapy session and its drug infusion. These symptoms are called anticipatory nausea and anticipatory vomiting. The present paper summarizes the evidence that anticipatory vomiting is acquired by Pavlovian conditioning, and, consequently, may be alleviated by conditioning techniques. To explore the mechanisms that induce and alleviate conditioned nausea and vomiting further, a conditioned nausea model was established in healthy humans using body rotation as the nausea-inducing treatment. The validity of this motion sickness model to examine conditioning mechanisms in the acquisition and alleviation of conditioned nausea was demonstrated. Cortisol and tumor-necrosis factor-alpha were elevated as endocrine and immunological correlates of nausea. Data in the rotation-induced motion sickness model indicated that gender is an important moderator variable to be considered in further studies. The paper concludes with a review of applications of the demonstrated conditioning principles as interventions to ameliorate distressing anticipatory nausea or anticipatory vomiting in cancer patients undergoing chemotherapy.

Overshadowing and latent inhibition of context aversion conditioning in the rat

A review is presented of experimental studies, using rats as the subjects, that were designed to establish an animal model of the clinical phenomenon of anticipatory nausea. Experiments 1 and 2 demonstrated that pairing a distinctive context with an illness-inducing injection of lithium chloride endowed the context with new properties, consistent with the proposal that classical conditioning had established an association between the context as the conditioned stimulus and nausea as the unconditioned stimulus. The conditioned response to the context constitutes a form of anticipatory nausea. Experiment 3 examined overshadowing, showing that the presence of a novel salient cue (a flavour) during context conditioning reduced the magnitude of the aversion conditioned to the context. Experiments 4-7 examined the effects of giving exposure to the context prior to conditioning. They demonstrated a latent inhibition effect, that is, a reduction in the magnitude of the aversion in pre-exposed animals. It is suggested that these ways of modulating conditioned aversions could form the basis of interventions for use in the chemotherapy clinic. Anticipatory nausea is assumed to be a consequence of the formation of an association between the cues that constitute the clinic and the drug-induced nausea experienced in their presence. By restricting the development of this association, latent inhibition and overshadowing procedures should be effective in alleviating the problem of anticipatory nausea.

The continuing problem of post chemotherapy nausea and vomiting: contributions of classical conditioning

Despite continuing improvements in antiemetic therapies, nausea and vomiting following chemotherapy treatments for cancer remain significant clinical problems for many patients. The role of classical conditioning in patients' anticipatory nausea is well known, but little attention has been paid to possible conditioning effects on post treatment nausea. The present study statistically examined the contribution of anticipatory (conditioned) nausea to patients' subsequent post treatment nausea. Forty early stage breast cancer patients who developed anticipatory nausea were analyzed. Results revealed a significant correlation between the intensity of anticipatory nausea in the clinic prior to their treatment infusion and subsequent post treatment nausea during the 24 h after the infusion. These results provide support for the hypothesis that, once established, conditioned nausea may contribute to the severity of subsequent post treatment nausea in patients receiving repeated cycles of chemotherapy for cancer. The results suggest the importance of considering the contribution of conditioning process to nausea and other post treatment side effects.

Behavioral conditioning with interferon beta-1a in humans

Behavioral conditioning is one of the most impressive demonstrations of brain-immune system interaction. Numerous animal studies have demonstrated behavioral conditioned effects on immune functions, however, human studies are rare. We investigated whether it is possible to behaviorally condition the acute response to interferon (IFN)beta-1a. In a double-blind placebo-controlled study, 30 healthy subjects received a single injection of IFN(beta)-1a (6MIU of REBIF, Serono International) (unconditioned stimulus, UCS) together with a novel drink (conditioned stimulus, CS). Blood was drawn at baseline, 4, 8, and 24 h after drug administration. Within the first 8 h peripheral granulocytes significantly increased, while monocytes, lymphocytes, T-, B- and natural killer (NK) cell numbers were significantly reduced. In parallel, body temperature, heart rate, norepinephrine and interleukin (IL)-6 plasma levels were heightened within 8 h after injection. 8 days later, all previously IFN(beta)-treated subjects received a subcutaneous placebo (NaCl) injection, but only 15 subjects were re-exposed to the CS (experimental group), while a control group (N=15) drank water and an additional group of subjects (n=8) remained untreated (untreated group). Blood sampling was performed at baseline and at 4, 8, and 24 h. Re-exposition to the CS did not elicit conditioned responses in the experimental group. Moreover, no differences were observed between groups. These data provide negative findings regarding behavioral conditioning of cytokine effects in humans employing a one-trial learning paradigm.

Latent inhibition of rotation chair-induced nausea in healthy male and female volunteers

OBJECTIVES

Pre-exposure to an environment in which a nausea-inducing body rotation will subsequently be given constitutes a latent inhibition procedure that might act to reduce anticipatory and postrotation nausea.

METHODS

This was tested in 24 healthy subjects randomly assigned to receive no pre-exposure (group 0), a single pre-exposure (group 1), or three pre-exposures (group 3). Rotation was standardized as 5 x 1 minute rotation, but the subjects could terminate it on request. Nausea was determined on a 7-item symptom rating scale before, during, and after rotation on days 3 and 4, whereas anticipatory nausea was measured before presumed rotation on day 5. Saliva cortisol and tumor necrosis factor alpha (TNF-alpha) levels were determined at baseline before, directly, and 15 and 30 minutes after rotation every day, and before presumed rotation on day 5.

RESULTS

Pre-exposure significantly reduced the degree of anticipatory nausea on day 5. Cortisol levels increased with rotation and were higher at baseline on days 4 and 5, but subjects habituated from day 3 to day 4; levels were lower in women than in men. In contrast, TNF-alpha decreased with rotation but showed no habituation. For both cortisol and TNF-alpha, no effects on postrotational nausea were found.

CONCLUSION

It is concluded that repetitive pre-exposure (latent inhibition) reduces anticipatory but not postrotation nausea; behavioral measures (rotation time) and measures of acute stress (cortisol, TNF-alpha) do not respond to latent inhibition. Thus, Pavlovian conditioning rules are effective in healthy humans with anticipatory nausea but not with postrotation nausea. Hormonal responses--TNF-alpha decrease with stress, compensatory cortisol increase--and gender-related effects on learning and habituation are discussed with regard to psychophysiological and psychoimmunological processes.

Anticipatory nausea and vomiting

Anticipatory nausea and vomiting (ANV) is not only a learned response but can occur without prior exposure to chemotherapy depending on patient emotional distress and expectations. The best method to avoid development or reinforcement of ANV is to avoid both vomiting and nausea from the first exposure to chemotherapy. If ANV develops, benzodiazepines have been documented to help in adult patients, and several psychological techniques are also of help, including systematic desensitization. The evidence on which these conclusions are based is reviewed in this article.

Postinjection suppression of drinking is modified by the presence of conditioned contextual cues: implications for both anticipatory and posttreatment nausea in humans

In three experiments, we set out to determine whether the response of rats to an injection of LiCl would be modified by the presence of an environmental context that had previously been paired with LiCl. Experiment 1 confirmed that one feature of the malaise produced by LiCl is a reduced tendency to consume an otherwise palatable flavor. Experiment 2 showed that the size of this response was enhanced if it was measured in the presence of a conditioned context. In Experiment 3, we investigated the possibility that the postinjection response could be modified by an overshadowing treatment given during the conditioning phase. The significance of these findings for the understanding of chemotherapy-induced nausea in the clinical population is discussed.

Pavlovian conditioning of taste aversion using a motion sickness paradigm

OBJECTIVE

Pavlovian conditioning of taste aversion has rarely been investigated in healthy humans using motion sickness as the unconditioned stimulus (US).

METHODS

Ninety subjects were pretested for susceptibility to illusory motion (vection) in a rotating drum. Thirty-two subjects susceptible to pseudomotion were assigned randomly to two groups and received either water 1 hour before rotation and a novel taste (elderberry juice, conditioned stimulus, [CS]) immediately before rotation in a rotating chair (conditioning group), or the sequence of water and juice was reversed (control group). During the test session 1 week later, all subjects were exposed to water 1 hour before and juice immediately before rotation. The amount of liquids ingested, nausea ratings, rotation tolerance, and blood levels of hormones (ACTH, ADH, PP) were evaluated.

RESULTS

Subjects in the conditioning group developed taste aversion toward the novel taste, but not subjects in the control group. Postrotation nausea rating was affected marginally by conditioning, but rotation tolerance was not changed by conditioning. ACTH and ADH but not PP levels increased with rotation, but were unaffected by conditioning.

CONCLUSIONS

Pavlovian conditioning of behavioral, but not of endocrine, indicators was effective in susceptible subjects using a rotating chair as US and a single CS-US pairing.

Anticipatory symptoms and anticipatory immune responses in pediatric cancer patients receiving chemotherapy: features of a classically conditioned response?

There is considerable evidence from studies in adult patients that classical conditioning contributes to anticipatory nausea and/or vomiting (ANV) in cancer chemotherapy: The stimuli predicting the infusion serve as conditioned stimuli (CS). When reexposed to the CS, some patients experience ANV prior to infusion onset. In adult patients, anticipatory immunomodulation (AIM) has also been observed. The present study examines whether ANV and AIM occur in pediatric cancer patients and whether they show features of a conditioned response.

METHODS

Nineteen pediatric cancer patients (M = 10.1 years, > 2 previous chemotherapies) were studied over two consecutive cycles (A, B). In both cycles, self-reported symptoms, for example nausea and vomiting, were recorded from two days prior to the onset (Day -2), during infusion, and two days after the end of the infusion (Day +2). In Cycle B, blood was drawn at home at Day -2, and at Day 0 in the hospital prior to infusion onset, thus using a quasi-experimental variation of the CS content of the environment. Immune parameters valid for tumor defense and cytotoxic competence (natural killer cell activity [NKCA], plasma interleukin [IL]-1beta, IL-2, IL-10, interferon [IFN]-gamma, tumor necrosis factor [TNF]-alpha) and cortisol were measured.

RESULTS

ANV was reported by 7 patients in at least one cycle. In Cycle A, ANV was positively associated with emetogenity of chemotherapy. Features of ANV-duration and occurrence-tended to be positively associated with those of posttreatment nausea and vomiting. AN increased as infusion onset time approached. NKCA and IFN-gamma increased from home to hospital, independent from cortisol level. The NKCA increase was predominantly observed in patients with ANV.

CONCLUSIONS

ANV in pediatric patients showed features of a CR. Immune parameters were sensitive to the CS content of the environment, predominantly in patients with ANV. This is consistent with the manifestation of multiple CRs.

Pavlovian conditioning of immune function: animal investigation and the challenge of human application

Pavlovian conditioning of immune functions provided early impetus to the rapidly expanding knowledge of bi-directional communication among the immune, endocrine, and central nervous systems. Since these early investigations, the phenomenology of this response has been well characterized. However the neural mechanisms and biological relevance of conditioned immunomodulation remain unclear. To this end, we present here data from our laboratories that have: (1) revealed some of the neural mechanisms and biological relevance of an animal model of conditioned immunomodulation; (2) demonstrated the conditionability and potential mechanisms of conditioned immune responses in healthy humans, and (3) investigated conditioned immunomodulation in a clinical sample. Together, these data demonstrate that animal models provide a basis for investigating mechanisms whereby conditioned changes in immune function may modulate health status in a clinical realm.

Summation of overshadowing and latent inhibition in rats' conditioned taste aversion: scapegoat technique works for familiar meals

In rats' taste aversion learning, presentation of another taste with a target taste alleviates aversion for the target taste (overshadowing), and exposure of a target taste prior to its conditioning alleviates aversion for that taste (latent inhibition). The present study demonstrated summation of these effects, resulting in the least aversion in the rats that had received both overshadowing and latent inhibition treatments. The finding that overshadowing and latent inhibition summate is contrary to the prediction by the comparator hypothesis that they counteract, as recently reported in conditioned suppression of licking in thirsty rats. The present result supports the employment of the so-called "scapegoat technique" in cancer patients receiving chemotherapy after taking familiar meals.