Took me a while to get back to this question. I didn’t know the answer so I looked up some papers. The short answer is, knowing this requires long follow-up periods which studies are generally not good at so we don’t have great answers. Definitely a significant number of people don’t stay better.
The longer answer is, probably about half of people need some form of maintenance treatment to stay non-depressed for more than a year, but our view of this is very confounded. Some studies have used normal antidepressant medications for maintenance, and some studies have tried additional rounds of TMS, both of which work really well. Up to a third of patients experience “symptom worsening” meaning that after an initial improvement from TMS, their symptoms actually get worse than when they started, but apparently more TMS can fix this in most people? I wasn’t completely sure what they were saying here. So yeah, it isn’t great. A lot of people need maintenance of some kind. This could very well correlate with whether your depression is the “life circumstances” kind or the “intrinsic brain chemistry” kind, not that we have a great handle on differentiating those two either.
Furthermore, (1) there are a few modes of TMS therapy out there, including most notably the accelerated course, and there may be different relapse rates across these treatment modes. There is some handwaving that the accelerated course may be more effective in this regard but I don’t think we know yet. And (2) another important issue with interpreting these data is that many of the studies are done on people who are treatment resistant, such as yourself. It’s unclear how much the results translate to the general population of depressed people.
Overall this is probably not a very satisfying answer, I don’t really have the specialist inside view on this one.
FYI the most targeted paper I found on this topic is the citation below. Note that it’s from 2016. There is probably something more recent, I just didn’t have more time to dig.
Sackeim, H. A. (2016). Acute continuation and maintenance treatment of major depressive episodes with transcranial magnetic stimulation. Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation, 9(3), 313-319.
Hey, I remember your medical miracle post. I enjoyed it!
”Objectively” for me would translate to “biomarker” i.e., a bio-physical signal that predicts a clinical outcome. Note that for depression and many psychological issues this means that we find the biomarkers by asking people how they feel...but maybe this is ok because we do huge studies with good controls, and the biomarkers may take on a life of their own after they are identified.
I’m assuming you mean biomarkers for psychological / mental health outcomes specifically. This is spiritually pretty close to what my lab studies—ways to predict how TMS will affect individuals, and adjust it to make it work better in each person. Our philosophy—which I had to think about for a bit to even articulate, it’s so baked into our thinking—is that the effects of an intervention will manifest most reliably in reactions to very simple cognitive tasks like vigilance, working memory, and so on. Most serious health issues impact your reaction times, accuracy, bias, etc. in subtle but statistically reliable ways. Measuring these with random sampling from a phone app and doing good statistics on the data is probably your best bet for objectively assessing interventions. Maybe that is what Quantified Mind does, I’m not sure?
The short answer is that if this were easy, it would already be popular, because we clearly need it. A lot of academic labs and industry people are trying to do this all the time. There is growing success, but it’s slow growing and fraught with non-replicable work.