Effects of Chronic Pain Diagnoses on the Antidepressant Efficacy of Transcranial Magnetic Stimulation.

OBJECTIVE: Major depressive disorder (MDD) and chronic pain are highly comorbid and bidirectionally related. Repetitive transcranial magnetic stimulation (rTMS) over the dorsolateral prefrontal cortex is effective in treating MDD, but additional research is needed to determine if chronic pain interferes with rTMS for MDD.

METHODS: Participants were 124 veterans (Mage = 49.14, SD = 13.83) scheduled for 30 sessions of rTMS across six weeks. Depression severity was monitored weekly using the Patient Health Questionnaire-9. Having any pain diagnosis, low back pain, or headache/migraine were assessed by chart review. We fit latent basis models to estimate total change by pain diagnosis in depression scores, and quadratic latent growth models to examine differences in growth rates. Then, we computed chi-square tests of group differences in response (PHQ-9 reduction ≥50%) and remission rates (final PHQ-9 < 5).

RESULTS: A total of 92 participants (74%) had a documented pain diagnosis, 58 (47%) had low back pain, and 32 (26%) had headache/migraine. In growth models, depression scores initially decreased (linear slope estimate = -2.04, SE = 0.26, p < .0001), but the rate of decrease slowed over time (quadratic slope estimate = 0.18, SE = 0.04, p < .001). Overall change was not different as a function of any pain diagnosis (p = .42), low back pain (p = .11), or headache/migraine (p = .28). However, we found that low back pain was a negative predictor of response (p = .032).

CONCLUSIONS: These data support rTMS as a viable treatment option for comorbid populations. While patients with comorbid chronic pain conditions are likely to receive benefit from rTMS for depression, adjunctive pain treatment may be indicated.