Transcranial magnetic stimulation (TMS) therapy was first introduced in 1985 and was based on principles established over a century prior by the Faraday experiment when Michael Faraday discovered electricity could generate a magnetic field in 1881. While the effects of an external electric current on the brain have been extensively researched in the past – forging the basis for ECT – transcranial magnetic stimulation was a step in an altogether different direction, eliciting a similar change in the brain without memory loss, induced seizures, or the need for muscle relaxants and anesthesia.
Based on previous research about deep brain stimulation and the effects of magnetic waves on the brain, TMS and dTMS/rTMS involve passing magnetic waves through the scalp into a portion of the brain over the course of approximately 30-minute sessions, several times per week. Just as Faraday’s experiments proved that a current can be induced in a circuit through changes in a nearby magnetic field, fluctuating or changing magnetic fields also induce changes in the brain’s neurons.
How TMS Affects the Brain
The exact mechanisms for TMS therapy are not completely understood. When experiments first began, noticeable changes were noted but the mechanism for the action could not be properly explained. Today, after much research, two possible hypotheses are commonly accepted as accurate explanations. One is that the magnetic waves used in TMS therapy affect certain neural pathways in the brain, interrupting and changing the signals sent through the brain, decreasing depression, and ‘normalizing’ a person’s mood.
To be more specific, brain imaging technology has allowed us to form a better understanding of how the brain is mapped out, and how certain parts of the brain interact with other parts to regulate everything from autonomous systems to emotions, thoughts, and motivation. Connections between portions of the prefrontal cortex and the hypothalamus are linked to such ideas and concepts, and these connections also link back to the amygdala, colloquially known as the ‘lizard brain’, through which we detect threats in split-second decision making.
Some research indicates that dysfunctions in the connections between portions of the prefrontal cortex connected to the hypothalamus and amygdala are linked to depressive disorders, as well as other neurobehavioral issues. Transcranial magnetic stimulation works by targeting the dorsolateral prefrontal cortex (DLPFC), ‘normalizing’ the activity of the connections between the DLPFC and the hypothalamus, and the amygdala and the DLPFC.
Other research indicates that another reason for depression is a problem in the facilitation of monoaminergic neurotransmission. Monoamine neurotransmitters are chemicals in the brain that are often linked to reward and moods, such as serotonin, dopamine, and epinephrine (adrenaline). The antidepressant medication works to inhibit the reuptake of these neurotransmitters yet may fail for one reason or another (genetic differences make certain individuals more or less susceptible to certain medication, even after trying several different types). TMS therapy may positively affect the availability of these neurotransmitters, thereby reducing depressive symptoms.
Either way, transcranial magnetic stimulation has proven effective particularly in the treatment of treatment-resistant depression, diagnosed in patients who have tried at least four different antidepressant drugs from two different types of antidepressants (two kinds of SSRIs and two kinds of SNRIs, for example).
Why TMS is an Alternative Treatment
While TMS is an FDA-approved treatment for depression, transcranial magnetic stimulation machines are not widely available, and the treatment can cost a lot out of pocket. Because many studies focused on TMS efficacy for treatment-resistant depression, most insurance companies only cover the costs of TMS therapy when other treatment methods have failed. Antidepressants continue to be the first-line treatment for depression because it is cheaper to administer and produce, still has very little in the way of side effects and is still found to be widely effective in most cases.
Sadly, there is no true cure for depression. Depression treatment must help reduce the symptoms of the disorder for a time, often long enough for depression to pass. But because a percentage of individuals with depression experience chronic or lifetime depression, their disorder must be continuously managed, often through a series of different treatments and therapeutic strategies, ranging from lifestyle changes to CBT and alternative treatments like TMS.
As research continues and the technology is improved, we can count on TMS being more widely available and accepted as a valid form of depression treatment.
How Is TMS Applied for Depression?
As of now, TMS therapy for depression involves scheduling several sessions per week for a total of about 20-30 sessions within a 4-6 week period. The effects of TMS are made long-lasting through the repeated application of the treatment. Each session takes roughly half an hour or less, and the first session is spent mapping out the exact portion of the brain that is to be targeted for the treatment.
After adjusting the machine accordingly, magnetic waves are passed through the skull by way of a special H-coil within the machine’s helmet, which the patient wears throughout the procedure. No anesthetics, medication, or preparation is necessary for TMS to work. It’s painless, non-invasive, and has no lasting side effects. Some patients may experience headaches as a result of the physical sensation of the magnetic waves passing through the scalp. This sensation has been described as a tapping or tingling sensation.
Patients are free to return to work or go straight home after each session. It’s safe to drive home after the treatment.
What About TMS Side Effects?
Unlike antidepressant medication, TMS doesn’t have lasting systemic effects as a result of its usage, such as weight gain or sexual dysfunction. The worst side effects reported for TMS include headaches, scalp discomfort, and temporary facial muscle spasms. Except for short headaches, these side effects are relatively rare and pass with subsequent treatment sessions. If they persist, the doctor may recommend taking over-the-counter pain medication to help with the headache.
TMS has no lasting side effects and very few special considerations. Because magnetic waves are used, TMS cannot be used to treat patients who have sensitive brain stimulation devices within their scalp, head, or neck, and TMS cannot be used to treat patients who possess other metal objects in their neck or head as a result of reconstructive surgery or other procedures. Dental braces and most fillings are typically okay, but it’s still recommended to thoroughly discuss your medical history with a doctor before undergoing TMS therapy to ensure that you do not have anything in or around your head that may interact with the magnetic waves of the device.