Miles Hill

Background: Post traumatic stress disorder (PTSD) and major depressive disorder (MDD) are among the most common psychiatric disorders that affect military service members (SMs) and veterans in the United States. SMs suffering from PTSD often have depression resistant to pharmacological therapies and present with additional comorbidities. These disorders negatively impact quality of life, contribute to the high risk of suicide seen in the Armed Forces, and reduce the military’s overall state of readiness. For these reasons, effective treatment options are needed for when pharmaceuticals fall short or are otherwise not an option. One such treatment is Repetitive Transcranial Magnetic Stimulation which works by inducing long term potentiation (LTP) effects through magnetic stimulation of the hippocampal network.¹

Objective: We reviewed different treatments utilizing TMS therapy to help patients suffering from PTSD and MDD.

Search Methods: An online search in the PubMed database was conducted from 2017 to 2023 using the following keywords: “PTSD”, ” Treatment resistant depression”, ” transcranial magnetic stimulation”, ” theta-burst transcranial magnetic stimulation”.

Results: Multiple studies were evaluated which utilized rTMS and its offshoot Theta-burst Transcranial Magnetic Stimulation (TBS) for their feasibility in being used as a viable treatment option for PTSD. The studies showed progressively positive results.^2-5 One study performed on aging mice showed that rTMS therapy increased memory function and neuron plasticity when compared to the control group.¹

Other studies evaluated used TBS on human patients suffering from PTSD and treatment resistant depression. The results showed that TBS therapy increased memory recall and reduced PTSD symptoms, both from a patient and clinician perspective.³ Additionally, these studies also focused on progressing brain monitoring ability so that brain activity could be actively monitored during and after therapy.

Conclusion: Despite demonstrating successful results, additional work is still required before rTMS and TBS can be adopted as first line treatments for PTSD. One of the largest weaknesses in these clinical trials using TBS is that they apply a specific frequency for a duration that is generally understood to be “good” to a general region of the brain that is associated with memory and is understood to be “good”. In other words, the parameters of TBS are not very precise. A possible path forward to improving TBS therapy is to drastically increase the number of clinical trials to acquire more data and then utilize machine learning algorithms to find the best and most optimized parameters (such as frequency, duration, precise location of stimulation).

Works Cited:

1. Ma J, Zhang Z, Kang L, et al. Repetitive transcranial magnetic stimulation (rTMS) influences spatial cognition and modulates hippocampal structural synaptic plasticity in aging mice. Exp Gerontol. 2014;58:256-268. doi:10.1016/j.exger.2014.08.011
2. Philip NS, Barredo J, van ‘t Wout-Frank M, Tyrka AR, Price LH, Carpenter LL. Network Mechanisms of Clinical Response to Transcranial Magnetic Stimulation in Posttraumatic Stress Disorder and Major Depressive Disorder. Biol Psychiatry. 2018;83(3):263-272. doi:10.1016/j.biopsych.2017.07.021
3. Philip NS, Barredo J, Aiken E, et al. Theta-Burst Transcranial Magnetic Stimulation for Posttraumatic Stress Disorder. Am J Psychiatry. 2019;176(11):939-948. doi:10.1176/appi.ajp.2019.18101160
4. Solomon EA, Sperling MR, Sharan AD, et al. Theta-burst stimulation entrains frequency-specific oscillatory responses. Brain Stimul. 2021;14(5):1271-1284. doi:10.1016/j.brs.2021.08.014
5. Hermiller MS, Chen YF, Parrish TB, Voss JL. Evidence for Immediate Enhancement of Hippocampal Memory Encoding by Network-Targeted Theta-Burst Stimulation during Concurrent fMRI. J Neurosci. 2020;40(37):7155-7168. doi:10.1523/JNEUROSCI.0486-20.2020