Mood disturbance is common among patients with fibromyalgia (FM), but the influence of psychological symptoms on pain processing in this disorder is unknown. We undertook the present study to investigate the differential effect of depressive symptoms, anxiety, and catastrophizing on 1) pain symptoms and subjective ratings of general health status and 2) sensitivity to pain and cerebral processing of pressure pain.
Eighty-three women (mean ± SD age 43.8 ± 8.1 years) who fulfilled the American College of Rheumatology 1990 criteria for the classification of FM participated in the study. Patients rated pain intensity (100-mm visual analog scale [VAS]), severity of FM (Fibromyalgia Impact Questionnaire), general health status (Short Form 36), depressive symptoms (Beck Depression Inventory), anxiety (State-Trait Anxiety Inventory), and catastrophizing (Coping Strategies Questionnaire). Experimental pain in the thumb was induced using a computer-controlled pressure stimulator. Event-related functional magnetic resonance imaging was performed during administration of painful stimuli representing 50 mm on a pain VAS, as well as nonpainful pressures.
A correlation analysis including all self-ratings showed that depressive symptoms, anxiety, and catastrophizing scores were correlated with one another (P < 0.001), but did not correlate with ratings of clinical pain or with sensitivity to pressure pain. However, the subjective rating of general health was correlated with depressive symptoms and anxiety (P < 0.001). Analyses of imaging results using self-rated psychological measures as covariates showed that brain activity during experimental pain was not modulated by depressive symptoms, anxiety, or catastrophizing.
Negative mood in FM patients can lead to a poor perception of one's physical health (and vice versa) but does not influence performance on assessments of clinical and experimental pain. Our data provide evidence that 2 partially segregated mechanisms are involved in the neural processing of experimental pain and negative affect.