MBM and taVNS for Low Back Pain and Depressive Symptoms

The pain intensity and interference will be measured by the brief pain inventory (BPI) and the NIH Patient-Reported Outcomes Measurement Information System (PROMIS) adults short form pain interference 8a measurement. There are 15 items in BPI with 4 items in pain intensity (worst, least, average, right now) and 7 items in pain interference (general activity, mood, walking ability, normal work, relations with other people, sleep, and enjoyment of life).

The patient health questionnaire (PHQ-9) will be used to measure depressive symptoms. The PHQ-9 is scored on a scale of 0 to 27, with higher scores indicating greater severity of depressive symptoms. A score of 5 to 9 indicates mild depression, 10 to 14 indicates moderate depression, 15 to 19 indicates moderately severe depression, and 20 or above indicates severe depression.

QST will be used to measure sensitivity to experimental pain with standardized stimuli to test both nociceptive and non-nociceptive systems following our previous protocol. QST consists of 7 tests measuring 13 parameters to assess and quantify the perception of temperature, touch, pain, vibration, and pressure.

CPM will be used to determine the net effect of various facilitating and inhibiting systems exerting their activity at spinal or supraspinal levels. A phasic noxious stimulus (cold) will be applied in conjunction with a tonic noxious conditioning stimulus (pressure) applied to a distant body site on the forearm. Participants' self-reported pain intensity by NRS during the test will be recorded.

Chronic Pain Self-Efficacy Scale (CPSES) will be used to measure pain self-efficacy with scores from 0-100, higher scores indicating improved self-efficacy.

Time Frame: Baseline and 2 weeks and 8 weeks

The Patient-Reported Outcomes Measurement Information System (PROMIS) profile will be used to measure the co-occurring symptoms, including anxiety, physical function, fatigue, and sleep disturbance. The response scores of each item will be summed for the total raw score; the raw scores will then be transferred to the standardized T-score with a mean of 50 and a standard deviation of 10 for the general population in the USA. The T-scores of PROMIS measures will be calculated following the NIH instruction, ranging from 0 to 100.

Cortical activity associated with pain stimuli will be assessed utilizing a continuous-wave, multichannel functional near-infrared spectroscopy (fNIRS) imaging system (LIGHTNIRS, Shimadzu, Kyoto, Japan) equipped with three semiconductor lasers emitting at 780, 805, and 830 nm. Optical data will be gathered while subjects undergo thermal pain stimulation.

The 16S rRNA V4 region will be amplified and sequenced by using stool samples to depict the fecal microbiota alpha diversity, beta diversity, and abundance of microbial taxa in the human gut.