Learning to Detect Triggers of Airway Symptoms: The Role of Illness Beliefs, Conceptual Categories and Actual Experience with Allergic Symptoms

Generalisation of Placebo and Nocebo Effects: Current Knowledge and Future Directions

BACKGROUND AND OBJECTIVE

Placebo and nocebo effects are beneficial or adverse treatment outcomes upon administration of inert treatment components. These effects have been frequently studied on pain. It remains unclear to what extent generalisation occurs in these effects on pain and other somatic sensations. This review outlines the current knowledge on stimulus generalisation (i.e., generalisation over various stimuli) and response generalisation (i.e., generalisation over various responses) of placebo and nocebo effects on prevalent somatic sensations (i.e., pain, itch, dyspnea, nausea and fatigue).

DATABASES AND DATA TREATMENT

The databases PubMed, Web of Science and PsycINFO were systematically searched for peer-reviewed articles reporting on experimental studies in humans of the induction and generalisation of placebo and nocebo effects on prevalent somatic sensations.

RESULTS

Of 2025 records identified, 23 studies were included. These studies indicated that placebo and nocebo effects can generalise over stimuli (at perceptual, categorical and treatment levels) and over responses within modalities. Most studies investigated pain; fewer studies investigated itch, dyspnea, nausea and fatigue. Generalisation effects tend to be larger when the generalisation stimuli and responses more closely resemble the initial stimulus or response. Generalisation was more likely if a combination of verbal suggestion and conditioning was employed to induce placebo or nocebo effects than if either suggestion or conditioning was employed alone. Response generalisation across modalities remains unclear.

CONCLUSIONS

Placebo and nocebo effects can generalise over stimuli and responses. More experimental and clinical research is warranted to address carryover effects of placebo and nocebo effects.

SIGNIFICANCE

The current review provides an overview of the literature on the generalisation of placebo and nocebo effects to diverse stimuli and responses. This can ultimately benefit healthcare providers to prevent carryover effects of treatment failure and harness carryover effects of treatment success.

Will that hurt? A contingency learning task to assess pain-expectancy judgments for low back postures

BACKGROUND AND OBJECTIVES

Contingency learning, i.e. learning that a cue predicts the presence (or absence) of an event, is central to the formation of beliefs regarding painfulness of body postures. Such beliefs may spread to safe cues due to compromised learning (e.g., excessive generalization, impaired safety learning), prompting avoidance and leading to disability. Despite its importance, compromised learning about low back pain is underinvestigated. We propose a low back pain scenario contingency learning task for the investigation of back pain-related learning.

METHODS

Sixty healthy participants viewed pictures of an avatar in various back postures, and for each posture gave pain-expectancy judgments and viewed the verbal outcome (pain/no pain) for a fictive back pain patient. During acquisition, one posture was followed by pain (conditioned stimulus; CS+), whereas another was not (CS-). During generalization, unreinforced novel intermediate back postures (generalization stimuli; GSs) were tested. During extinction, only the CSs were presented, not followed by pain. During generalization of extinction, only the GSs were presented, not followed by pain.

RESULTS

Participants expected pain more for the CS + than the CS- (differential acquisition) and generalized their pain-expectancy to the GS most similar to the CS+ (generalization). During extinction, pain-expectancy for the CS + decreased and generalized to the GS most similar to the CS+ (generalization of extinction).

LIMITATIONS

Future research should investigate generalizability of findings to clinical samples and consider the role of pre-existing pain threat beliefs.

CONCLUSIONS

This task is an easily applicable, non-invasive way to investigate the formation of back pain-related threat beliefs.

Antipruritic Placebo Effects by Conditioning H1-antihistamine

OBJECTIVE

Allergic rhinitis symptoms can be reduced by behaviorally conditioning antihistamine. It is unclear whether these findings extend to histamine-induced itch or work when participants are informed about the conditioning procedure (open-label conditioning). The current study aims to investigate the efficacy of (open-label) antipruritic behavioral conditioning for histamine-induced itch.

METHODS

Healthy participants (n = 92; 84% female) were randomized to I) an open-label conditioned, II) closed-label conditioned, III) conditioned-not-evoked control, or IV) nonconditioned control group. A two-phase conditioning paradigm was used. During acquisition, a conditioned stimulus (CS; distinctively tasting beverage) was repeatedly paired with the H1-antihistamine levocetirizine (groups I-III). During evocation, the CS was paired with placebo (I, II), or instead of the CS, water was paired with placebo (III). The nonconditioned control group (IV) received CS with placebo in both phases. Itch after histamine iontophoresis and physiological data (i.e., spirometry, heart rate, skin conductance) were assessed. Combined conditioned and combined control groups were first compared, and analyses were repeated for separate groups.

RESULTS

Marginally lower itch was reported in the combined conditioned compared with the control groups (F(1,88) = 2.10, p = .076, ηpartial = 0.02); no differences between separate groups were found. No effects on physiological data were found, except for heart rate, which reduced significantly and consistently for control groups, and less consistently for conditioned groups (group by time interaction: F(7,80) = 2.35, p = .031, ηpartial = 0.17).

CONCLUSION

Limited support was found for the efficacy of antipruritic behavioral conditioning, regardless of whether participants were informed about the conditioning procedure. The application of open-label conditioning in patient populations should be further researched.

TRIAL REGISTRATION

www.trialregister.nl; ID NTR5544.