Anxiety as a Psychological Modulator of Endogenous Pain Inhibition in Chronic Neck Pain: Implications for Precision Rehabilitation

Carla S Enriquez,1– 3 Alka Bishnoi,1 Musola N Oniyide,4 Katherine L Jennings,1 Roger Luo5,6 1Department of Physical Therapy, Kean University, Union, NJ, USA; 2Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, USA; 3Department of Physical Therapy, Cooperman Barnabas Medical Center-Robert Wood Johnson (RWJ) Barnabas Health, Livingston, NJ, USA; 4Department of Physical Therapy, Overlook Medical Center, Summit, NJ, USA; 5Department of Physical Medicine & Rehabilitation, Cooperman Barnabas Medical Center-Robert Wood Johnson (RWJ) Barnabas Health, Livingston, NJ, USA; 6Department of Physical Medicine & Rehabilitation, Rutgers-New Jersey Medical School, Newark, NJ, USACorrespondence: Carla S Enriquez, Department of Physical Therapy, Kean University, 1000 Morris Avenue, North Avenue Academic Building, Union, NJ, 07083, USA, Tel +1 908 737-6186, Email cenrique@kean.eduObjective: Chronic neck pain (CNP) is a highly prevalent musculoskeletal disorder with significant personal and socioeconomic impact. In conjunction with low back pain, CNP accounts for the highest healthcare expenditures in the United States and contributes to 3551 disability‑adjusted life years per 100,000 population globally. This study explores the relationship between psychological factors and pain processing mechanisms, assessed through Quantitative Sensory Testing (QST), in individuals with CNP.Design: Cohort study.Setting: Hospital-based comprehensive outpatient rehabilitation center.Participants: Forty-one adults diagnosed with nonspecific CNP who presented to physical therapy for initial examination.Interventions: Not applicable.Main Outcome Measures: Primary predictors were anxiety and pain catastrophizing; secondary predictors included demographics and self-reported pain and disability. Primary outcomes were central pain processing assessed via Quantitative Sensory Tests (QST) through measures of mechanical Pressure Pain Threshold (PPT) and Conditioned Pain Modulation (CPM).Results: Generalized additive model analysis revealed a significant nonlinear association between anxiety and PPT (edf = 3.56, F = 3.25, p = 0.030), suggesting possible threshold effects. For CPM, the model explained 26.5% of deviance (adjusted R2 = 0.155), with anxiety showing a significant linear association (edf = 1.00, F = 4.93, p = 0.036), indicating its role in altered pain modulation.Conclusion: Our findings highlight anxiety as a key psychological factor influencing pain modulation in chronic neck pain. Targeting anxiety may enhance endogenous pain control, informing both preventive and therapeutic strategies. Early identification of anxiety in patient care may influence clinical decision-making, inform patient education and counseling strategies, as well as influence decisions regarding targeted preventive strategies, advanced imaging, procedural interventions, or referrals to specialty care.Keywords: chronic neck pain, precision rehabilitation, quantitative sensory testing, conditioned pain modulation, pain processing, anxiety, pain catastrophizing