Pretreatment pupillary reactivity is associated with outcome of Repetitive Transcranial Magnetic Stimulation (rTMS) treatment of Major Depressive Disorder (MDD).

Background: Pre-treatment biomarkers for outcome of repetitive Transcranial Magnetic Stimulation (rTMS) treatment of Major Depressive Disorder (MDD) have proven elusive. One promising family of biomarkers involves the autonomic nervous system (ANS), which is dysregulated in individuals with MDD.

Methods: We examined the relationship between the pre-treatment pupillary light reflex (PLR) and rTMS outcome in 51 MDD patients. Outcome was measured as the percent change in the 30-item Inventory of Depressive Symptomatology Self Rated (IDS-SR) score from baseline to treatment 30.

Results: Patients showed significant improvement with rTMS treatment. There was a significant correlation between baseline pupillary Constriction Amplitude (CA) and clinical improvement over the treatment course (R = 0.41, p = 0.003).

Limitations: We examined a limited number of subjects who received heterogeneous treatment protocols. Almost all patients in the study received psychotropic medications concomitant with rTMS treatment.

Conclusion: PLR measured before treatment may be a predictive biomarker for clinical improvement from rTMS in subjects with MDD.