TMS (Transcranial Magnetic Stimulation) for Depression

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What it is

Transcranial magnetic stimulation (TMS) is a noninvasive treatment that uses magnetic pulses to stimulate specific parts of the brain that are involved in mood regulation and depression 1. TMS is approved by the U.S. Food and Drug Administration (FDA) for treating major depressive disorder (MDD) and obsessive-compulsive disorder (OCD), and it may also be helpful for other conditions such as bipolar disorder, migraines, and smoking cessation 2 3 4.

TMS was first developed in 1985 by Anthony Barker and his colleagues at the University of Sheffield in England. They used a magnetic coil to induce electric currents in the brain of a healthy volunteer and demonstrated that TMS could alter brain activity and behavior. Since then, TMS has been used as a research tool to study various aspects of brain function, such as language, memory, attention, and emotion.

In the 1990s, researchers began to explore the therapeutic potential of TMS for treating neuropsychiatric disorders, especially depression. The first randomized controlled trial of TMS for depression was published in 1996 by Mark George and his colleagues at the Medical University of South Carolina . They found that TMS applied to the left prefrontal cortex, a brain region associated with mood regulation, was more effective than sham stimulation in reducing depressive symptoms. Since then, many studies have confirmed the antidepressant efficacy of TMS, and several devices have been approved by the FDA for clinical use.

The exact mechanism of action of TMS is not fully understood, but it is believed to involve several processes at different levels of the brain. At the cellular level, TMS induces changes in the electrical activity and neurotransmitter release of neurons, which can modulate their synaptic plasticity and connectivity. At the network level, TMS alters the functional interactions among brain regions, which can enhance or inhibit their communication. At the behavioral level, TMS influences cognitive and emotional processes, such as attention, memory, decision making, and mood.

The antidepressant effect of TMS is thought to result from stimulating the left dorsolateral prefrontal cortex (DLPFC), a brain region that is often underactive in people with depression. By increasing the activity and connectivity of the DLPFC, TMS may restore its normal function in regulating mood and emotion. Additionally, TMS may also affect other brain regions that are involved in depression, such as the limbic system, which mediates emotional responses, and the default mode network, which relates to self-referential thoughts.

TMS has been extensively studied as a treatment for depression, and there is strong evidence to support its effectiveness and safety. A meta-analysis of 81 randomized controlled trials involving 4,271 participants found that TMS was significantly more effective than sham stimulation in reducing depressive symptoms, with a moderate effect size. The response rate (the proportion of participants who achieved at least a 50% reduction in symptoms) was 29.3% for TMS versus 18.6% for sham stimulation. The remission rate (the proportion of participants who achieved a score below a certain threshold on a depression scale) was 16.9% for TMS versus 10.1% for sham stimulation.

TMS has also been shown to be effective as an add-on treatment for patients who do not respond adequately to antidepressant medication. A large multicenter trial involving 301 participants found that adding TMS to medication was more effective than medication alone in reducing depressive symptoms, with a response rate of 38% versus 21%, and a remission rate of 14% versus 5%.

Furthermore, TMS has been demonstrated to have long-term benefits for patients with depression. A follow-up study of 257 participants who received acute TMS treatment found that 68% maintained their response after one year, and 45% maintained their remission. The relapse rate (the proportion of participants who experienced a recurrence of depressive symptoms) was 37%. Most participants received maintenance TMS sessions during the follow-up period to prevent relapse.

TMS is generally well tolerated and has few side effects. The most common side effect is scalp discomfort or pain at the site of stimulation, which usually subsides after the first few sessions or can be alleviated by adjusting the stimulation parameters. Other possible side effects include headache, facial twitching, dizziness, nausea, and fatigue. These side effects are usually mild and transient, and do not require discontinuation of treatment.

The most serious risk of TMS is inducing a seizure, which is very rare and occurs in less than 0.1% of patients . The risk of seizure can be minimized by following the safety guidelines and screening procedures for TMS, and by avoiding factors that may lower the seizure threshold, such as alcohol, drugs, sleep deprivation, and certain medications.

TMS is contraindicated for patients who have metal implants or devices in or near the head, such as pacemakers, cochlear implants, aneurysm clips, or shrapnel. These may interfere with the magnetic field or cause heating or movement of the implant, which could result in injury or malfunction. TMS is also contraindicated for patients who have a history of epilepsy, stroke, brain tumor, or other neurological conditions that may increase the risk of seizure or adverse effects.

TMS has several advantages over other treatments for depression, such as medication and electroconvulsive therapy (ECT). Some of these are:

• TMS is noninvasive and does not require anesthesia or sedation, which means that patients can remain awake and alert during the treatment and resume their normal activities afterward.
• TMS does not cause systemic side effects, such as weight gain, sexual dysfunction, nausea, or dry mouth, which are common with antidepressant medication and may affect adherence and quality of life.
• TMS does not cause cognitive impairment or memory loss, which are potential complications of ECT and may affect functioning and well-being.
• TMS is personalized and adjustable, which means that the stimulation parameters can be tailored to each patient’s individual needs and preferences and modified according to their response and tolerance.
• TMS is durable and sustainable, which means that the antidepressant effect can last for a long time after the treatment course is completed and can be maintained with periodic booster sessions.

TMS also has some limitations and drawbacks as a treatment for depression, such as:

• TMS is expensive and not widely available, which means that access to the treatment may be limited by cost or location. The average cost of a TMS session in the U.S. is about $400-$500, and a typical course of treatment consists of 20-30 sessions. Insurance coverage for TMS varies depending on the provider and policy.
• TMS is time-consuming and inconvenient, which means that patients have to commit to frequent and lengthy visits to the clinic. A typical TMS session lasts for 20-40 minutes, and patients usually receive treatment five times a week for four to six weeks.
• TMS is not effective for everyone, which means that some patients may not respond to the treatment or may relapse after a period of remission. The response rate of TMS is about 30%, which is comparable to that of antidepressant medication, but lower than that of ECT. The relapse rate of TMS is about 40%, which is similar to that of medication and ECT.
• TMS is not well understood and standardized, which means that there is still uncertainty about the optimal stimulation parameters, protocols, targets, and outcomes for different patients and conditions. There is also variability in the quality and efficacy of different TMS devices and operators.

TMS is a promising treatment option for patients with depression who do not respond well to conventional therapies. It has been proven to be effective and safe in reducing depressive symptoms and improving mood. It has several benefits over other treatments, such as being noninvasive, free of systemic side effects, cognitively benign, personalized, adjustable, durable, and sustainable. However, it also has some limitations and challenges, such as being expensive, inaccessible, time-consuming, inconvenient, variable in response and relapse rates, and incompletely understood and standardized. Therefore, more research is needed to improve the accessibility, affordability, convenience, effectiveness, consistency, and understanding of TMS for depression.

1: Transcranial magnetic stimulation - Mayo Clinic 

2: TMS treatment for depression: What to know - Medical News Today

3: Transcranial magnetic stimulation (TMS): Hope for stubborn depression

4: Transcranial Magnetic Stimulation (TMS) for Bipolar Disorder - Healthline : Barker AT et al. Non-invasive magnetic stimulation of human motor cortex. Lancet 1985; 1:1106–1107. : George MS et al. Daily repetitive transcranial magnetic stimulation (rTMS) improves mood in depression. Neuroreport 1996; 6:1853–1856. : Lefaucheur JP et al. Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS). Clin Neurophysiol 2014; 125:2150–2206