Transcranial magnetic stimulation (TMS) is a non-invasive procedure that uses magnetic fields to stimulate nerve cells in the brain. Schizophrenia is a complex, chronic mental health disorder characterized by disruptions in thought processes, perceptions, emotional responsiveness, and behavior. Because existing medications often fail to treat all symptoms, researchers are exploring novel interventions like TMS. This article examines the regulatory status and scientific basis for its potential use in schizophrenia.
Current Regulatory Approval Status
The United States Food and Drug Administration (FDA) has not granted approval for transcranial magnetic stimulation as a treatment for schizophrenia. FDA approval requires extensive clinical evidence demonstrating both the safety and efficacy of a device for a specific patient population and condition. This rigorous process ensures that the benefits of the treatment outweigh its risks for the intended use.
The FDA has, however, cleared TMS devices for the treatment of several other conditions. These currently include Major Depressive Disorder, which was the first indication approved in 2008. Subsequent regulatory clearances expanded its use to include Obsessive-Compulsive Disorder, migraine headaches, and smoking cessation.
The regulatory clearance of TMS for other conditions provides context for the device’s established safety profile. Despite this, the lack of a specific FDA indication means that using TMS for schizophrenia is considered “off-label.” Off-label use is based on a clinician’s judgment and available research, but it is not officially sanctioned by the FDA.
The Mechanism of Transcranial Magnetic Stimulation
Transcranial magnetic stimulation operates on the principle of electromagnetic induction to modulate neural activity. The procedure involves placing a specialized magnetic coil against the patient’s scalp, typically shaped like a figure-eight. When an electrical current is rapidly discharged through this coil, it generates a powerful, time-varying magnetic field that passes painlessly through the skull.
This rapidly changing magnetic field induces a localized electrical current in the underlying brain tissue. This induced current is what ultimately stimulates the cortical neurons, causing them to either depolarize or hyperpolarize. The effect on the neurons depends on the specific protocol used, such as the frequency and intensity of the magnetic pulses.
When TMS is delivered repeatedly, it is known as repetitive TMS (rTMS), and it can produce longer-lasting changes in neural excitability. High-frequency stimulation (over 5 Hertz) tends to increase cortical excitability. Conversely, low-frequency stimulation (1 Hertz or less) tends to decrease it, allowing researchers to non-invasively excite or inhibit specific brain regions.
Investigational Use in Managing Schizophrenia Symptoms
Because standard pharmacological treatments do not provide relief for all individuals with schizophrenia, rTMS has become an active area of clinical investigation. Researchers are focusing on specific symptoms that are often resistant to medication, which include both positive and negative symptoms of the disorder. The goal is to correct the abnormal neural activity patterns thought to underlie these specific manifestations.
One major area of research targets persistent auditory hallucinations, which are experienced by a significant number of individuals despite taking medication. Studies often focus on the temporoparietal cortex, specifically the superior temporal gyrus, which is hypothesized to be overactive in people experiencing these “voices.” In these trials, low-frequency rTMS is often applied to this area to inhibit the presumed hyperactivity.
Another important focus is the treatment of negative symptoms, such as apathy, social withdrawal, and blunted emotional responses, which are particularly disabling for patients. These symptoms are associated with dysfunction in the frontal lobes, particularly the dorsolateral prefrontal cortex (DLPFC). Researchers commonly apply high-frequency rTMS to the left DLPFC in an attempt to increase the activity in this hypoactive brain region.
The results from these clinical trials have been mixed, with some showing a significant reduction in symptoms while others have not reached the same conclusion. The inconsistent findings are often attributed to the wide variation in study design. These variations include differences in stimulation frequency, the targeted brain area, and the number of treatment sessions used across studies.