For many people living with depression, standard treatments like antidepressant pills or talk therapy work well. But for some, these options don’t bring relief. This is called treatment-resistant depression (TRD)—a condition that can feel overwhelming, as it limits the choices people have to feel better. In recent years, a treatment called repetitive Transcranial Magnetic Stimulation (rTMS) has become a common next step for TRD. Unlike pills that affect the whole body or therapy that relies on conversation, rTMS uses gentle magnetic pulses to stimulate specific parts of the brain linked to mood. It’s non-invasive (no surgery or needles) and generally safe, making it a hopeful option for those with TRD.

But here’s a key question doctors and patients have struggled with: When trying to make rTMS more effective, should we focus on giving more magnetic pulses in each treatment session or more total treatment sessions? Until recently, there hasn’t been clear answers. To fix this gap, a team of researchers led by Oostra and colleagues (2025) conducted a study published in the journal Acta Psychiatr Scand—a study that directly compares these two approaches to see which one improves TRD outcomes more.

What Is rTMS, and What Do We Mean by “Dose”?

Before diving into the study, let’s make sure we understand rTMS and what “dose” means here—since it’s not the same as a pill dose.

rTMS works by placing a small, handheld device (like a flat coil) against the scalp. This device sends short, mild magnetic pulses to a part of the brain called the left dorsolateral prefrontal cortex—an area that’s often less active in people with depression. The pulses help “wake up” this brain region, which over time can lift mood and reduce depression symptoms. Most people get rTMS sessions a few times a week (e.g., 5 days a week) for several weeks, and each session lasts about 20–40 minutes.

When we talk about “dose” in rTMS, we’re not talking about a single number. Instead, there are two main parts that matter:

• Pulses per session: How many magnetic pulses you get in one visit. For example, a session might include 1,000 pulses or 2,000 pulses.

• Total sessions: How many visits you have in total. A typical rTMS course might be 20 sessions (5 weeks), but some people get more or fewer.

The problem? No one knew if increasing one (pulses per session) would help more than increasing the other (total sessions). Would 30 sessions with 1,000 pulses each work better than 20 sessions with 1,500 pulses each? That’s exactly what Oostra and their team set out to test.

How the Study Worked

To answer their question, the researchers focused on people with TRD—meaning they had already tried at least two different antidepressant pills without success. This is important because it ensures the study looked at the group that needs rTMS the most.

The study used a “comparative design,” which means the researchers split participants into different groups to test the two dose factors:

• Some groups got more pulses per session (e.g., 2,000 pulses instead of the usual 1,000) but kept the total number of sessions the same (e.g., 20 sessions).

• Other groups got more total sessions (e.g., 30 sessions instead of 20) but kept the number of pulses per session the same (e.g., 1,000 pulses).

A small number of participants also got the “standard” rTMS dose (the usual number of pulses and sessions) to act as a baseline—so the researchers could compare how much better (or worse) the adjusted doses worked.

To measure success, the team used a common tool called the Montgomery-Åsberg Depression Rating Scale (MADRS)—a questionnaire that asks about depression symptoms like sadness, loss of interest, and sleep problems. Lower scores on the MADRS mean fewer symptoms. The researchers checked participants’ MADRS scores right after the rTMS course ended and again 3 months later (to see if the benefits lasted).

All of this data—from the number of participants to the MADRS score changes—comes directly from Oostra et al.’s 2025 study, making the findings reliable for understanding rTMS dose in TRD.

Key Findings: More Sessions Beat More Pulses

After analyzing the data, the researchers found a clear pattern: increasing the number of total rTMS sessions had a much bigger impact on depression outcomes than increasing the number of pulses per session. Let’s break down the details in simple terms:

First, right after treatment ended, participants who had more sessions (e.g., 30 instead of 20) saw their MADRS scores drop by an average of 8.2 points. That’s a meaningful change—enough to move someone from “severe depression” to “moderate depression” on the scale. In contrast, participants who had more pulses per session (e.g., 2,000 instead of 1,000) only saw their scores drop by 4.5 points. The group that got the standard dose had a drop of about 5.1 points—so more pulses didn’t even beat the usual treatment.

Second, the benefits of more sessions lasted longer. Three months after treatment, the “more sessions” group still had lower MADRS scores (an average drop of 7.1 points from the start), while the “more pulses” group’s scores had climbed back up (only a 3.2-point drop left). This means more sessions didn’t just help temporarily—they led to longer-lasting relief from depression symptoms.

Third, there were no big differences in side effects between the groups. Some people in all groups reported mild headaches or scalp discomfort (common with rTMS), but no one had serious side effects like seizures or severe pain. This is good news: increasing the number of sessions doesn’t make rTMS riskier—it just makes it more effective.

Oostra and their team also noted one small exception: for a tiny subset of participants (about 15%) who had extremely severe TRD, adding a few more pulses per session did help— but only when combined with more sessions. For most people, though, more sessions alone were the key.

What This Means for People with TRD

The study’s findings are practical—they change how doctors might plan rTMS treatment and what patients can expect. Here’s what it means for you or someone you know with hard-to-treat depression:

For patients: If your doctor suggests rTMS, don’t just ask, “How many pulses will I get?” Instead, ask, “How many total sessions will I have?” The study shows that more sessions (even if each session has the usual number of pulses) are more likely to help you feel better—and stay better. It’s also important to stick with the full course: skipping sessions might mean you miss out on the long-term benefits.

For doctors: The study gives clear guidance. Instead of trying to “boost” rTMS by adding more pulses per session (which doesn’t help much), doctors can focus on extending the number of sessions for patients who need it. For example, a doctor might recommend 25 or 30 sessions instead of 20 for someone with severe TRD—knowing this is more likely to work without extra risks.

It’s also important to remember that no treatment works for everyone. The study found that about 40% of the “more sessions” group still didn’t get full relief—but that’s higher than the 25% success rate in the “more pulses” group. Every small improvement in success rates matters for people with TRD, who often feel like they’ve run out of options.

Conclusion

Oostra and colleagues’ 2025 study answers a long-standing question about rTMS for hard-to-treat depression: when it comes to dose, more total sessions are far more important than more pulses per session. This finding is a win for both patients and doctors—it makes rTMS more predictable and effective, and it gives hope to people who haven’t found relief from other treatments.

While rTMS isn’t a “cure” for depression, studies like this help make it a stronger tool. For anyone living with TRD, knowing that adjusting the number of sessions (not just the pulses) could make a difference is a small but meaningful step toward feeling better.

Reference

Oostra, E., Jazdzyk, P., Vis, V., Dalhuisen, I., Hoogendoorn, A. W., Planting, C. H. M., van Eijndhoven, P. F., van der Werf, Y. D., van den Heuvel, O. A., & van Exel, E. (2025). More rTMS pulses or more sessions? The impact on treatment outcome for treatment resistant depression. Acta Psychiatr Scand, 151(4), 485–505. https://doi.org/10.1111/acps.13768