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Does TMS really work for depression?

Transcranial Magnetic Stimulation (TMS) has been used against depression for several decades, yet there remains scepticism among both patients and doctors over whether it really works.

To help address this gap, Neurocentrix recently ran a study of TMS in depression, but with a twist.  Almost all existing TMS studies have looked at a very select group of patients in a very specific setting, namely depression where other treatments have failed.  While these studies provide important evidence that TMS does work, they also reinforce the assumption that TMS is mostly for research or intractable cases.  Patients with other conditions or using other treatments are excluded as much as possible from these trials, but in reality, most people who need treatment will have these features and many more.  Previous trials have also been restricted to the specific TMS protocol under investigation, with the same intensity, frequency, site and number of sessions.  In practice these vary enormously.  In the real world neither the patients nor the treatments fit the box that research decrees.


The Study

And so, this study took all patients who had received TMS for whatever reason, and then assessed the effect retrospectively.  Patients were neither handpicked nor excluded.  The result was a large sample that represented real-life patients receiving TMS in a real-world setting.  The patients were assessed with rating scales at admission and discharge, and these numbers were analysed and compared.  The total number of participants was 229, with 135 women and 94 men.  They were of all ages, ranging from 19 to 89.  104 of the participants had more than one admission, and these further admissions were also included.  A review of the patient files indicated that each participant had been experiencing moderate to severe depressive symptoms, and major depressive disorder was the most common primary diagnosis.

Yet depression alone is not the only way to be depressed, and many patients suffer depressive symptoms from another disorder.  And so, in this study featured a variety of conditions encompassing the whole range of psychiatric pathology, including alcohol abuse, ADHD, OCD, bipolar disorder, schizophrenia and personality disorders.  The only patients not included in the sample were those which could not be compared because of missing data, such as an incomplete discharge assessment.


The Results

Once all the statistical analyses were complete, the results of the study were clearly positive.  Across all measures, symptoms of depression had decreased after TMS treatment.  Not only did the results easily pass the test for statistical significance, but the improvement was substantial.  On average, a patient’s change in score was sufficient to move down one or two severity ranges, such as from severe to moderate or mild.  Statistical analysis also revealed that the initial treatment produced a larger effect than subsequent treatments, which fits the expected law of diminishing returns.  Another important outcome of the study was that patients who recorded a mild severity of depression also benefited.  Since most studies have involved patients with severe or treatment-resistant depression, this finding fills in a crucial gap in existing research.  Overall, the conclusion was unequivocal: an admission for TMS treatment has a significant antidepressant effect.


The Analysis

A potential criticism of the study is that patients may have improved from whatever treatment they had during their stay, not necessarily the TMS.  Here is one drawback of the “real-world” approach.  By not excluding patients that receive other treatments, the benefit of these treatments would be lumped in with the TMS.  However, this criticism is not as strong as it appears since any other treatment would usually already be in place before admission, and any treatment changes would be coincidental and insignificant compared to the reason for the admission, the TMS itself.  Changes to medication or psychotherapy, for example, do not require admission and could occur at any time, thus having no effect on the period under study.  In fact, such changes would be more likely to occur apart from, rather than during, an admission for TMS.

Psychiatrists generally change only one treatment at a time, or there would be no way of knowing which change was responsible for the outcome.  Such caution would be even more tightly applied when undertaking a novel and time-consuming treatment like TMS, since the understanding its impact would be crucial in deciding future management.  Meanwhile in the hypothetical cases where medications were changed during admission, any resulting benefit would likely not appear until well after discharge.  A new antidepressant, for example, takes 4 to 6 weeks to reach its effect, which would accordingly not influence the assessment taken at discharge.

Another concern would be that patients might not leave until improved, and thus depression scores would naturally be better at discharge than admission.  Ideally patients would improve during their stay, but this is not how admissions occur in practice.  Length of stay is usually capped regardless of outcome, and admissions for TMS are generally planned for a set period.  The depression score at discharge therefore escapes this potential bias.  In fact, since discharge is often shortly after treatment, the discharge assessment may underestimate the benefit by assuming that any effect happens immediately.  Neuroscientific studies on the effects of TMS suggest a complex pathway that involves several much slower mechanisms, such as synaptic growth and restored neuronal connectivity.  Together these processes fall under the term “neuroplasticity”, a phenomenon that takes weeks or even months to develop and would certainly remain invisible to an assessment taken at discharge.


TMS Therapy Options

While the study cannot remain impervious to all criticisms, the size of the effect strongly suggests that overall, the positive result is sound.  The study indicates that TMS is effective for depressive symptoms over a large sample size which includes a variety of comorbidities, diagnoses, medications, lengths of stay, treating clinicians, protocols employed, and treatments delivered.  We can comfortably conclude that TMS is a viable and effective option for depressed patients in the real world.