A case control series for the effect of photobiomodulation in patients with low back pain and concurrent depression

Background and aims: To present incidental findings in patients with low back pain (LBP) who received photobiomodulation (PBM) administered to the back and thighs as an adjunct to physical therapy (PT) and then experienced improvement in concurrent depression. Materials and methods: Five outpatients with LBP and concurrent self-reported depression were treated for LBP over five weeks with PT (5-sessions) and concurrent PBM (final 3-sessions), and retrospectively matched to five control patients treated with PT alone (5-sessions). The PBM device emitted light at 850nm and 660 nm with an irradiance of 100 mW/cm² and fluence of 3 J/cm² on 12 symmetrical posterior sites (thoracic, lumbar and thighs) for 30 sec/site. Results: Both groups had non-significant differences in all baseline scores, except for higher functional status (ARGS) in the PBM-group (33.6 ± 12.2 vs.18.6 ± 3.6, t(8) = 2.638, p = 0.030). After treatment, the mean decrease in depression scores (OMSQ-12 item #6) was significantly larger in the PBM-group (43.0 ± 22.0 vs. 8.0 ± 5.7, t(8) = 3.449, p = 0.009). Improvement in functional status (ARGS) in the PBM-group was similar to that in the controls (42.0 ± 13.5 vs. 43.4 ± 11.1, t(8) = 0.179, p = 0.862), suggesting group differences in antidepressant effect were independent of functional status improvement. Conclusions: This preliminary investigation suggests that an antidepressant effect may result from PBM to the back and thighs in patients with LBP and concurrent depression.