1. 2020;23;E703-E712The Result of Acute Induced Psychosocial Stress on Pain Sensitivity and Modulation in Healthy People
   Observational Study
   Mira Meeus, PhD, Filip Struyf, PhD, Geert Crombez, PhD, Jessica Van Oosterwijck, PhD, MSc, Lotte Meert, MSc, Michel Mertens, MSc, and Linda Hermans, MD, PhD.

BACKGROUND: Pain can be influenced by several factors, including stress. Stress can have various reactions on pain. These reactions are influenced by several internal factors such as gender, age, and experience with stress or pain.

OBJECTIVES: To determine the effect of acute stress on mechanical hyperalgesia (with pressure pain thresholds [PPT]), endogenous pain facilitation (measured by temporal summation [TS]), and inhibition (measured by conditioned pain modulation [CPM]) in healthy people and to determine which factors are responsible for this stress result.

STUDY DESIGN: Pre-posttest design.

SETTING: Healthy volunteers from Belgium.

METHODS: One hundred and one healthy pain-free patients underwent a modified Trier Social Stress Test. Prior and following the stress manipulation, PPT, TS, and CPM efficacy were determined in the mm. trapezius and quadriceps and overall. Furthermore, possible explanatory factors, such as fear of pain, pain catastrophizing, pain hypervigilance, and daily activity levels, were assessed using questionnaires.

RESULTS: We found a significant stress result on widespread pain sensitivity, with an increase of PPT (P < 0.001), unchanged TS (P > 0.05), and a decrease in CPM efficacy (P < 0.001). Factors associated with the stress result were age, previous surgery, attentional focus on the conditioning stimulus during CPM, fear of pain, and daily activity levels.

LIMITATIONS: The efficacy of the stress manipulation was not examined, and the lack of a control group prevented to examine a real stress-effect. Furthermore, no physiologic parameters were measured as possibly influencing internal factors for the stress-result.

CONCLUSIONS: The increase in PPT was not a clinically significant change, whereas the decrease in CPM was meaningful. None of the factors predicted the stress result in all experimental pain measurements, and the predictions that were observed only explained a small proportion of the observed effects.

KEY WORDS: Psychosocial stress, pain sensitivity, pain modulation, pain inhibition, pain facilitation,  moderator, predictor, healthy people