Affective immunology of the skin is a growing area; however, established protocols for measuring individual differences in cutaneous inflammation are lacking. To address this, we present a preliminary validation of Precision Implementation of Minimal Erythema Dose (PI-MED) testing as a method for measuring cutaneous inflammation. PI-MED is a recently adapted protocol, optimized for reproducibility and individual differences research, that uses ultraviolet (UV) light to evoke cutaneous erythema, or inflammatory skin reddening. PI-MED’s novel UV dosage schedule produces standardized erythema responses across different skin pigmentation types and shows strong internal consistency within person and good test–retest reliability across 8–10 weeks. In line with predictions, increased PI-MED erythema was associated with heightened anhedonia, across several measures, beyond influences of non-affective covariates. While future work should further refine the dosage schedule for the lightest and darkest skin types, overall, evidence supports PI-MED as a protocol for inducing and measuring individual differences in cutaneous inflammation. Further, PI-MED-induced erythema can expand psychoneuroimmunology research by offering a complementary assessment for general inflammatory tone. This work adds to a growing body of evidence demonstrating a distinct relationship between inflammation and anhedonia.
Background: There is growing interest in affective immunology of the skin; however, investigations are limited by the lack of an established protocol for measuring cutaneous inflammation that is suitable for individual differences research. Methods: To address this gap, we present a preliminary validation of Precision Implementation of Minimal Erythema Dose (PI-MED) testing as a method for measuring cutaneous inflammation. PI-MED is a recently adapted protocol, optimized for reproducibility and individual differences research, that uses ultraviolet (UV) light to evoke cutaneous erythema, or inflammatory skin reddening. Results: As intended, PI-MED’s novel UV dosage schedule produced reasonably standardized erythema responses across different skin pigmentation types (thus facilitating individual differences research). Further, the PI-MED erythema measure showed strong internal consistency within person and good test-retest reliability across 8-10 weeks. In line with predictions, increased PI-MED erythema was associated with heightened anhedonia, across several anhedonia measures, controlling for non-affective covariates. Limitations: The PI-MED dosage schedule needs further refinement for the lightest and darkest skin types. As PI-MED erythema showed only weak associations with some known covariates of other measures of inflammation, future work should explore relationships between PI-MED erythema and other measures of peripheral inflammation and their covariates.Conclusions: Overall, evidence supports PI-MED as a protocol for inducing and measuring individual differences in cutaneous inflammation, and PI-MED has potential to expand psychoneuroimmunology research to better understand immunological and affective processes in the skin. Further, this work adds to a growing body of evidence demonstrating a distinct relationship between inflammation and anhedonia.
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