How Does TMS Therapy Work? The Science Behind Treatment-Resistant Depression Treatment

April 3, 2026

How Does TMS Therapy Work? The Science Behind Treatment-Resistant Depression Treatment

For the estimated 30% of individuals with major depressive disorder who do not respond adequately to antidepressant medications, finding an effective path forward can feel daunting. Transcranial Magnetic Stimulation (TMS) has emerged as an FDA-cleared, non-invasive treatment option that offers renewed hope for those living with treatment-resistant depression (TRD). But many patients and families want to understand how TMS therapy works before committing to a new course of treatment. At Hagan Health in Louisville, KY, our team is dedicated to providing that clarity so patients can make informed decisions alongside their healthcare providers.

This guide breaks down the science, the process, and what patients can expect when pursuing TMS therapy for treatment-resistant depression.

What Is Transcranial Magnetic Stimulation?

TMS is a non-invasive brain stimulation technique that uses targeted magnetic pulses to stimulate specific regions of the brain associated with mood regulation. Unlike medications that travel through the entire body, TMS is a non-systemic treatment, meaning it directly targets the brain without introducing chemicals into the bloodstream. The procedure does not require anesthesia, sedation, or any surgical intervention, and patients remain fully awake and alert throughout each session.

First cleared by the FDA in 2008 for treating major depressive disorder in adults who have not responded to prior antidepressant medication, TMS has since gained broader recognition as a viable option for treatment-resistant depression. As of 2026, growing clinical evidence and expanding insurance coverage continue to make TMS more accessible to patients across Louisville and the surrounding region.

How TMS Differs from Other Depression Treatments

Traditional approaches to depression treatment typically begin with psychotherapy, antidepressant medications, or a combination of both. While these methods are effective for many people, a significant portion of patients do not experience sufficient relief-even after trying multiple medications from different classes. This is what clinicians refer to as treatment-resistant depression.

TMS occupies a unique middle ground between medication and more intensive interventions like electroconvulsive therapy (ECT). It does not require anesthesia, does not cause systemic side effects commonly associated with antidepressants (such as weight gain, sexual dysfunction, or drowsiness), and does not involve any recovery downtime. Patients can drive themselves to and from appointments and resume daily activities immediately after each session.

The Science Behind How TMS Therapy Works

Understanding how TMS therapy works begins with the brain itself. Depression is associated with underactivity in the left dorsolateral prefrontal cortex (DLPFC), a region involved in mood regulation, decision-making, and emotional processing. In patients with depression, nerve cells in this area often show diminished signaling compared to those without the condition.

Magnetic Pulses and Neural Stimulation

During a TMS session, an electromagnetic coil is placed against the scalp near the forehead, positioned over the left DLPFC. The coil generates brief, focused magnetic pulses-similar in strength to those used in magnetic resonance imaging (MRI)-that pass painlessly through the skull and into the targeted brain tissue. These pulses induce small electrical currents in the neurons of the prefrontal cortex, causing them to fire and become active.

Over the course of repeated sessions, this repetitive stimulation has been shown to promote lasting changes in neural activity. The brain responds through a process known as neuroplasticity-its ability to reorganize and strengthen neural connections over time. Essentially, TMS may help “retrain” underactive brain circuits involved in mood regulation, gradually restoring more typical patterns of activity.

Deep TMS Technology

Advancements in TMS technology have led to the development of deep TMS, which uses specialized coil designs to reach broader and deeper areas of the brain compared to traditional surface-level TMS. Deep TMS allows clinicians to stimulate neural pathways that may be more directly involved in the complex circuitry of depression. Hagan Health utilizes deep TMS technology to provide Louisville-area patients with this advanced form of treatment.

Who May Benefit from TMS Therapy?

TMS therapy is specifically indicated for adults with treatment-resistant depression-typically defined as individuals who have not achieved adequate relief after trying one or more antidepressant medications. It is not generally used as a first-line treatment but rather as a next step when standard approaches have not produced the desired results.

Candidates for TMS may include individuals who:

  • Have been diagnosed with major depressive disorder
  • Have tried antidepressant medications without sufficient improvement
  • Experience intolerable side effects from antidepressant medications
  • Are seeking a non-invasive, non-systemic alternative to medication
  • Want to continue their current therapy or medication regimen alongside TMS

It is important to note that TMS may not be appropriate for individuals with certain metal implants in or near the head, or those with a history of seizure disorders. A thorough evaluation with a qualified provider is essential to determine whether TMS is a suitable option for any individual patient.

What to Expect During a Course of TMS Treatment

Knowing how TMS therapy works in practice-from the first consultation through the final session-helps patients feel prepared and confident as they begin treatment.

Initial Evaluation

Before starting TMS, patients undergo a comprehensive evaluation at Hagan Health. This includes a review of medical history, current medications, past treatment responses, and overall mental health status. The treating clinician uses this information to develop a personalized treatment plan and to determine the appropriate stimulation parameters for each patient.

Treatment Sessions

A standard course of TMS therapy typically involves daily sessions (Monday through Friday) over approximately six weeks, followed by a tapering period. Each session generally lasts between 20 and 30 minutes, during which the patient sits comfortably in a treatment chair. The electromagnetic coil is positioned on the scalp, and the patient may hear clicking sounds and feel a tapping sensation at the treatment site.

There is no sedation or anesthesia involved. Patients remain fully conscious and can read, listen to music, or simply relax during the session. Once the session is complete, patients are free to leave the office and continue their normal routines-including driving, working, and exercising-without any recovery period.

Side Effects

TMS is generally well tolerated. The most commonly reported side effects are mild and tend to diminish over the first week or two of treatment. These may include:

  • Mild scalp discomfort or soreness at the treatment site
  • Headache following the session
  • Lightheadedness

Serious side effects are rare. Because TMS does not enter the bloodstream, it avoids the systemic side effects associated with many antidepressant medications. This is one of the primary reasons patients and providers alike consider TMS an appealing option for managing treatment-resistant depression.

What Does the Evidence Say About TMS Effectiveness?

A growing body of clinical research supports the use of TMS for treatment-resistant depression. Published studies and real-world clinical data suggest that many patients experience meaningful improvement in depressive symptoms after completing a full course of treatment. National data from 2026 indicates that approximately 50–60% of TMS patients with treatment-resistant depression show a significant clinical response, and a notable subset may achieve full remission of symptoms.

It is important to set realistic expectations: TMS does not work for everyone, and results vary from patient to patient. Some individuals notice improvement within the first few weeks, while others may not experience changes until later in the treatment course or shortly after completing it. TMS is not a permanent cure for depression, and some patients may benefit from maintenance sessions or continued therapy and medication management after their initial course of treatment.

Consulting with a qualified provider is the best way to understand how TMS therapy works in the context of an individual’s unique medical history and treatment goals.

Insurance Coverage for TMS Therapy

As recognition of TMS therapy’s clinical value has grown, so has insurance coverage. TMS is often covered by insurance for treatment-resistant depression, and Hagan Health accepts several major insurance providers, including Aetna, Cigna, TRICARE, Medicare, Anthem, and Beacon/Carelon. Patients are encouraged to reach out to Hagan Health directly to discuss their specific coverage and eligibility.

Why Louisville Patients Choose Hagan Health for TMS Therapy

Hagan Health, located at 4010 Dupont Circle, Suite 202, in Louisville, KY, provides TMS therapy in a professional, patient-centered clinical setting. The practice brings specialized expertise to every patient interaction, and the care team is committed to helping individuals with treatment-resistant depression explore whether TMS may be a beneficial addition to their treatment plan.

Serving patients throughout Louisville and the greater Jefferson County area, Hagan Health combines advanced deep TMS technology with individualized treatment planning to support each patient’s journey toward improved mental health. The practice’s clinical team works closely with patients to monitor progress throughout the course of treatment and to adjust care as needed.

Take the Next Step Toward Understanding Your Options

If you or a loved one has been living with treatment-resistant depression and previous medications have not provided adequate relief, learning how TMS therapy works may be the first step toward finding a more effective path forward. TMS is a non-invasive, non-systemic treatment that has helped many individuals experience meaningful improvement in their depressive symptoms.

Contact Hagan Health today to schedule a consultation and find out whether TMS therapy may be right for you. The team is ready to answer your questions, explain the treatment process in detail, and help you make an informed decision about your mental health care.

smoking

Smoking Addiction

BrainsWay Deep TMS is a noninvasive, FDA-cleared, outpatient brain stimulation procedure with proven clinical results to help patients to quit smoking.  Known as the addiction coil, the H4 coil was specifically designed for targeting the deep areas of the brain involved in addictions.

A large study in 14 centers examined adults who had been long-term heavy smokers, all having failed prior quit attempts using medication, therapy, or other methods. Of those that completed Deep TMS treatment, 28% achieved four consecutive weeks without smoking, most of them not smoking for at least three months after treatment.  Among all participants in the study, the average number of cigarettes smoked per week over the course of treatment was reduced by 75%.  

TMS has none of the side effects commonly found in medication to treat smoking cessation. TMS is well-tolerated with years of safety data supporting Deep TMS. Patients may initially experience minor headaches or pain at the site of treatment which typically subside after the first few sessions. There is no preparation, no anesthesia, and patients are able to resume daily activities immediately after each treatment session. Treatments are done in our office. Each treatment session lasts 25-30 minutes. They are done daily on weekdays for 3 weeks followed by a weekly session for another 3 weeks.

BrainsWay Deep TMS offers a fresh approach that may help to quit smoking using cutting-edge neuroscience. Clinically proven and well-tolerated, Deep TMS is the first non-invasive technology that is FDA-cleared to treat smoking addiction.

addiction

OCD

Deep TMS has recently be approved by the FDA for treatment of obsessive-compulsive disorder (OCD).  OCD traditionally has been treated primarily with exposure psychotherapy, and while it is also treated with medication such as fluvoxamine, OCD does not respond well to medication management.  Medication improves symtpoms greater than 30% in only 50% of patients, and half of OCD patients stop taking their medication due to side effects.  And while exposure therapy might improve OCD, as many as 80% of patients continue to have symptoms after psychotherapy, according to some studies.

BrainsWay Deep TMS is a noninvasive, FDA-cleared, outpatient brain stimulation procedure with proven clinical results for improving the symptoms of OCD.  The technology stimulates the brain using its patented H-coil, known as the H7 coil, resulting in a deep and broad penetration of the magnetic field into areas of the brain that are affected in OCD. Deep TMS is safe and well-tolerated, has a very low rate of side effects, and does not require anesthesia.  

Research has proven a higher level of improvement using Deep TMS.  Almost 68% of OCD patients were able to reduce symptoms by more than 30%, and 87% of those who responded saw sustained improvement for at least a year.

depression

Depression

Major depression was the diagnosis first approved for treatment with TMS, and it is still the most commonly treated condition. Most patients are treated with TMS after failures of medications and psychotherapy, as insurance companies will pay for TMS treatment only after medication failures.  However, TMS treats depression much better than medication, and some would argue that TMS should be the first treatment instead of the last.  

When patients have not improved with medication, they are considered to be “treatment-resistant”. And in treatment-resistant depression, TMS treatment results in significant improvement, defined as more than a 50% reduction in symptoms, in more than 80% of patients.  And more than 60% of patients achieve remission.  That is a very high and a very impressive number of people who are happy for the first time in many years after TMS treatment.

TMS treatments for depression are done in a series of 36 treatments.  Patients have a 20-minute treatment 5 days a week for six weeks followed by 6 more treatments in a tapering schedule over three more weeks. No preparation is needed, and there is no recovery time.  After each treatment, patients are able to leave and go about their day.  Except for a rare seizure, which occurs in 1 of 1000 patients, TMS has only minor side effects of mild headache or scalp soreness in the first few days. 

It is said that after successful TMS treatment, that there is a 50% chance of relapse of depression within the first year.  However, at Hagan Health we consider that statistic to be too high, and our relapse rate is lower.  While treatments are done by certified and experienced treaters, Dr. Hagan is closely involved in determining the location and strengths of settings to provide the most accurate treatment.  In addition, Dr. Hagan meets with patients every week or two before and during treatment, and periodically after treatment, in order to insure the best possible results.  Depression varies from patient to patient, and it is important to get the know the patient and the thoughts, feelings, and circumstances that might lead to relapse.  Using cognitive therapy techniques, patients are taught to be aware of triggers and to be prepared with the cognitive tools used to reduce the chances of relapsing. 

TMS for Anxious Depression

Recently TMS has been cleared by the FDA for treatment of Anxious Depression.  This condition is one in which anxious distress is a major part of the clinical picture while depression remains the predominant diagnosis.  Anxiety which is treated along with depression is also significantly improved, while TMS is not currently considered appropriate for the treatment of anxiety without depression.

Dr. Hagan Bio

So the lesson Al taught me was about my lack of happiness related to feelings of inadequacy. Even though I had become a brain surgeon, I did not have a healthy self-regard. Al explained to me that my father, in his drive to succeed and to push me to succeed, would never let me savor a victory, that whenever I achieved something important, he would ask, . “How could you have done it better?” Or “what is next?”. He was setting the bar at perfection, such that nothing less than perfection was going to be good enough. Al said, “Nobody is perfect”, and that I would be much happier deciding what degree of imperfection I was going to settle for. When one sets the bar at perfection, then every effort falls short of perfection and is therefore a relative failure, it becomes yet more evidence of one’s belief that he is fundamentally flawed and inadequate. He said that we are all always doing our best, and that is not fair for my father or for me myself to tell myself that I am not good enough. It was the single most important piece of wisdom that I would learn for the next several decades, and I have told this story many times to those who, like me, grew up to have similar issues.

After seeing Al for a year, another year or two went by. One day at church I was listening to a talk from a psychotherapist who had grown up in a family in which his mother was an alcoholic and his father was a workaholic. His story sounded so much like mine that I decided to see him professionally to “learn more about this garbage in my head”. I saw Paul for two years.

A few years later, life had become quite stressful. I was married with three small children, practicing neurosurgery full time and doing some farming on the side. It was at this time that I started seeing my third therapist, the one that I would see for most of the next 10 years. Keith was a psychiatrist, an MD like me, who did only psychotherapy. A few months after starting my therapy with Keith, I realized that I liked what he did better than what I did. The process of therapy is that of developing an increasing awareness of how one got to be the way he or she is, starting with childhood issues. Specifically, this type of therapy is called “psychodynamic psychotherapy”.

Dr_Hagan
Terry

Three years into my experience with Keith, I made the final decision that I would rather be a psychiatrist, because I came to love the process of developing insight into one’s own psychology. As I closed my neurosurgery practice and completed a residency in psychiatry, I was so grateful the entire time for the opportunity to turn myself into a psychiatrist. “Who gets to do that?!” Years later a patient was looking at the books on my bookshelf and asked, “So you were a neurosurgeon; did you like it?” I had been asked many times why I decided to give up neurosurgery to become a psychiatrist, but no one had ever asked if I liked neurosurgery. The answer had to be that no, I did not. I did not like who I was. But I have loved psychiatry from the very beginning, and I really appreciate the contribution it has had in my own personal development.

But because of my heavy early experience in psychotherapy, I also became proficient and experienced in both psychodynamic psychotherapy and in cognitive behavioral therapy (CBT). And I attended the Cincinnati Psychoanalytic Institute for a year to take my psychotherapy skills to a higher level.

During the 17 years that I have been practicing psychiatry, I have continued to grow. The most gratifying experiences I have had have been when I have settled into a psychotherapy relationship with a patient, while there have been many, others with whom I have combined psychiatry with psychodynamic therapy, practicing psychodynamic psychiatry.

Terry
Dr. Hagan Bio

During these same years, I have also been on several mission trips, which have given me perspectives that I would never have learned otherwise. The concepts of loving your neighbor, giving of your time and resources, being kind and gentle and gracious, have come to define me.

I have always been at the head of my own practice, managing my own business. I have experience with other businesses as well, such as being a successful alpaca breeder for 10 years. “They do not teach business in medical school.” In a growing psychiatry practice, running the business is something you learn from necessity.