Positive affect and distraction enhance whereas negative affect impairs pain modulation in patients with recurrent low back pain and matched controls

Pathophysiological causes of low back pain (LBP) remain generally unclear, so focus has shifted to psychosocial features and central pain processing. Effects of attentional and affective manipulation on conditioned pain modulation and tonic pain perception were examined in 30 patients with recurrent LBP in 2 sessions, one with and one without clinical pain, and compared with healthy participants. Phasic cuff pressure on one leg, scored on a Numerical Rating Scale, was used for test stimuli, and contralateral tonic cuff pain rated on an electronic Visual Analogue Scale was the conditioning stimulus (CS). Test stimuli were assessed before and during (1) control with no manipulation or CS, (2) 3 attentional manipulations (Flanker with or without CS or CS-Only), and (3) 3 affective manipulations (positive, neutral, and negative images) with CS. Greater inhibition of test stimuli Numerical Rating Scale scores was observed in CS-only (P = 0.028), combined CS&attention (P = 0.026), and CS&Positive (P = 0.006) than control paradigms, and greater in CS&Positive (P = 0.019) than CS&Negative paradigms. Electronic Visual Analogue Scale scores of CS pain increased throughout all paradigms with CS (P < 0.05), except the CS&Positive paradigm, and greater facilitation was observed in the CS-Only paradigm than all others (P < 0.02), and lower facilitation was additionally observed in the CS&Positive paradigm compared with CS&Attention and CS&Negative paradigms (P < 0.01). Flanker effects and interruptive effects of CS pain on attention were observed consistent with prior findings, and affective manipulation produced less shift in valence among people with recurrent LBP than controls (P < 0.05). Attention and positive affect with CS pain evoked conditioned pain modulation, and all attentional or affective tasks, especially positive affect, reduced facilitation of CS pain.