Abstract
Background: Delay discounting (DD) refers to the decrease of a present subjective value of a future reward as the delay of its delivery increases. Major depressive disorder (MDD), besides core emotional and physical symptoms, involves difficulties in reward processing. Depressed patients often display greater temporal discounting rates than healthy subjects. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique applied in several countries to adult patients with treatment resistant depression. Studies suggest that this technique can be used to modulate DD, but no trial has assessed its effects on depressed patients. Methods: In this open-label uncontrolled trial, 20 patients diagnosed with MDD and at least stage II treatment resistance criteria underwent 20 HF-rTMS sessions over the dorsolateral prefrontal cortex (dlPFC; 10 Hz, 110% MT, 20 min). Pre-post treatment DD rates were compared. Effects on impulsivity, personality factors, and depressive symptoms were also evaluated. Results: No significant effect of HF-rTMS over the left dlPFC on DD of depressed individuals was observed, although rates seemed to increase after sessions. However, treatment resulted in significant improvement on cognitive impulsivity and depressive symptoms, and was well-tolerated. Conclusion: Despite the limitations involved, this pilot study allows preliminary evaluation of HF-rTMS effects on DD in MDD, providing substrate for further research.
Highlights
Major depressive disorder (MDD) is a widespread psychiatric disease that will become the leading worldwide cause of years living with disability by 2030 according to the World Health Organization (WHO)
The present study found no significant effect of 20 HF-Repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (dlPFC) on temporal impulsivity of patients diagnosed with MDD and meeting at least stage II criteria for treatment resistance
Confounding factors could influence the results due to the open-label uncontrolled study design and potentially compromise internal validity. These preliminary findings might be useful for directing further research in the field because our study is strengthened by well-defined eligibility criteria for the investigated population, outcome assessment by validated instruments only, and the adjustment of confidence intervals for multiple comparisons
Summary
Major depressive disorder (MDD) is a widespread psychiatric disease that will become the leading worldwide cause of years living with disability by 2030 according to the World Health Organization (WHO). Depressed subjects highly value immediate rewards despite being offered a larger, albeit relatively delayed reward, which suggests changes on reward valuation [2,3,4]. Major depressive disorder (MDD), besides core emotional and physical symptoms, involves difficulties in reward processing. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique applied in several countries to adult patients with treatment resistant depression. Studies suggest that this technique can be used to modulate DD, but no trial has assessed its effects on depressed patients. Results: No significant effect of HF-rTMS over the left dlPFC on DD of depressed individuals was observed, rates seemed to increase after sessions. Conclusion: Despite the limitations involved, this pilot study allows preliminary evaluation of HF-rTMS effects on DD in MDD, providing substrate for further research
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