Around the second or third week of TMS treatment, a patient will sometimes message me — usually late at night — saying something close to this: "I'm not sure if it's the treatment or something else, but I feel worse this week than I did before we started." There is often an apology attached, as if telling me this is somehow letting the treatment, or me, down.

It isn't. What they're describing is a recognized clinical phenomenon, common enough that I now mention it during the first consultation so it doesn't blindside anyone. In TMS clinics it's often informally called the TMS dip — a temporary worsening of mood, energy, or sleep that shows up partway through the treatment course, in patients who go on to do well.

The dip is poorly explained almost everywhere it's described. Marketing pages skip past it, internet forums catastrophize it, and most clinical brochures don't mention it at all. The result is that patients who experience it often think the treatment is failing — and a meaningful number of people consider stopping at exactly the point where they should be continuing.

This article is the description I give patients about what the dip actually is, why it happens, what it feels like, what we do about it, and how to tell it apart from the small minority of cases where worsening is a real warning signal that needs immediate clinical attention.

What the TMS dip actually is

The TMS dip is a transient worsening of depressive symptoms — typically lasting a few days to about a week — that occurs at some point in the first three weeks of an otherwise progressing TMS course. The patient's baseline shifts down for a brief window, and then either spontaneously or with small protocol adjustments, it shifts back up and continues climbing.

The picture varies by patient. Some describe a flat, blunted feeling — the early hopefulness of starting treatment recedes, energy drops, and the world feels grayer than it did a week earlier. Others describe disrupted sleep — falling asleep fine but waking unusually early, or sleeping more hours but feeling unrefreshed. A smaller number describe brief irritability, tearfulness, or a return of intrusive thoughts they thought had eased up.

What unites these presentations is that they are time-limited. The dip resolves. In most patients it resolves within five to seven days, often without any change to the protocol — and what comes after the dip is usually the most pronounced clinical improvement of the course.

Why it happens — the working clinical explanation

The honest answer is that we don't have a single, fully validated mechanism for the TMS dip. What we do have is a coherent working model that fits the timing and the pattern.

TMS works by repeatedly stimulating a specific cortical region — typically the left dorsolateral prefrontal cortex in depression — and over many sessions, this stimulation drives neuroplastic change in the broader networks that connect to it. The depressive brain network is, at the start of treatment, organized in a way that maintains the depressive state. Over a few weeks, repeated stimulation begins to reorganize that network into a healthier configuration.

The leading hypothesis for the dip is that network reorganization is not a smooth, monotonic process. As old connectivity patterns weaken and new ones form, the network passes through a brief window of relative instability — a few days where the old pattern has loosened but the new one hasn't fully consolidated. During that window, the patient is neither stably depressed nor stably improved. They feel it as a dip.

A second contributing factor for some patients is what I'd call emotional unmasking. Severe depression often blunts emotional range across the board — including the ability to fully feel grief, anger, or anxiety that has been chronically suppressed. As the depression begins to lift, those previously dampened emotions can surface for the first time in months or years. Patients sometimes describe this as "feeling sad in a different way than the depression sadness" — and clinically, that's often a hopeful sign even though it's uncomfortable.

A third factor is more mundane but worth naming: small sleep disruptions in the early weeks of TMS, often from changes in evening energy levels, can themselves transiently lower mood. Sleep tends to settle by the third week.

None of these mechanisms are mutually exclusive. In any given patient the dip is probably a mix of them.

When it typically shows up

The most common window is week two through early week three — sessions 6 through 12, roughly. Some patients experience an earlier dip in the first week, which in my clinical experience is more often a side-effect cluster (scalp tenderness, mild headaches, fatigue from the new routine) misread as a mood change. Some experience it later, in week three.

Patients who experience the dip earlier in treatment tend to come out of it earlier as well. Patients who experience it later in the course often have a shorter dip but a more dramatic improvement on the other side. Neither pattern predicts a worse final outcome.

A meaningful subset of patients — perhaps 30 to 40 percent in my practice — never experience a noticeable dip at all and improve in a steady, gradual line through the course. So the absence of a dip is not a sign that the treatment isn't working either. It just means the network reorganization is happening more smoothly for that particular brain.

What it actually feels like — the patient's experience

The most common descriptions I hear:

"I felt fine in the first week, almost optimistic, and now I feel flatter than I did at the start."

"I'm sleeping more but waking up tired."

"I had a really good day on Wednesday and then a bad three days that came out of nowhere."

"Everything I was hoping for last week feels naive now."

"I'm crying about things I haven't cried about in a long time."

None of these are signs that TMS isn't working. Most are signs that something is changing — and change, even change toward recovery, is not always pleasant in the moment.

What I want to flag carefully, though, is the distinction between the dip and a different and more serious pattern: new or worsening suicidal thoughts. Treatment-emergent suicidal ideation is a known if rare phenomenon with several depression treatments, and it requires immediate clinical contact — not waiting it out, not assuming it's the dip. If at any point during your TMS course you notice new thoughts of harming yourself, or existing thoughts that intensify in frequency or specificity, contact your treating clinician the same day. This is not the dip. This is a separate clinical event that needs evaluation.

What we do about it clinically

When a patient flags the dip, the first thing I do is verify the picture — confirm the timing relative to treatment start, screen for the warning patterns above, check sleep, check what's happened in their personal life that week, and review the protocol parameters we're running.In most cases, the answer is continue treatment unchanged. 

The dip resolves on its own, the next two weeks are usually when the strongest improvement appears, and changing protocol parameters during a brief instability window can make outcome interpretation harder.

In a smaller subset of cases, we make a calibrated adjustment. This might mean a small reduction in stimulation intensity for two or three sessions, adjusting coil position by a few millimeters if there has been any positioning drift, adding or adjusting a sleep-supporting intervention, or reviewing whether a concurrent medication change has contributed to the picture.

We rarely stop a course because of a dip alone. Stopping at this point in treatment is the single most common reason for a TMS course to fail to deliver its expected outcome — not because the dip itself is dangerous, but because the patient discontinues just before the improvement curve takes off.

What you should do as a patient

Three things, in order.

One — flag it to your treating clinician. Don't wait for the next scheduled review. A short message or call describing what you're noticing is the right move. We almost always want to hear about it the day it starts, even if the answer is "this is the dip, here's what to expect over the next few days.

"Two — keep showing up. The single most important predictor of TMS outcome is completing the course at the prescribed frequency. Missing sessions during the dip — exactly when motivation is lowest — is the failure pattern we work hardest to prevent. If getting to the clinic feels harder than it did in week one, that is itself part of the dip and is also temporary.

Three — protect the basics. Sleep regularity, hydration, daylight exposure, and gentle physical activity all support the brain's reorganization work. None of these will resolve the dip on their own, but skipping them tends to deepen it. If you're sleeping poorly during this window, raise it — sleep is one of the most fixable contributors.

How to tell the dip apart from non-response

This is the question patients ask most often, and it's a fair one. The honest answer is that the distinction is often only clear in retrospect — but there are patterns that help.The dip is time-limited. It has a beginning, a middle, and an end, usually inside a 5–10 day window. Non-response is a flat line — no improvement, no worsening, just a steady absence of change across multiple weeks.The dip occurs against a background of some early signal. Most patients who experience the dip had at least small positive changes in week one — slightly better sleep, slightly more energy, slightly less morning heaviness — that the dip then briefly erases. Patients who never noticed any change before the dip are a different clinical picture and warrant a closer review.

The dip resolves with continued treatment, often clearly. By the end of week three, you typically know whether what you were experiencing was the dip (you're now feeling better than your pre-treatment baseline) or something else (you're back at baseline with no upward trend).

Real non-response — the picture where TMS doesn't help — usually becomes evident around the end of week four. At that point we have several options: protocol adjustment, switching to a different TMS protocol, augmenting with another treatment, or moving to a different modality entirely. Even non-response in TMS is not a clinical dead end.

What the literature says

The TMS dip is described in clinical practice more than it is in the published literature, partly because most clinical trials report aggregate scores at fixed time points (week 2, week 4, week 6) rather than the daily symptom variation that would capture a transient mid-course worsening. The patients who experience a dip and recover end up looking, on a week-4 endpoint, identical to patients who improved smoothly.

The phenomenon is, however, consistent with what the broader neuromodulation literature describes about network reorganization timelines — the observation that brain networks under repeated stimulation pass through phases of decreased stability before settling into a new, more functional configuration. This pattern is described across rTMS, ECT (where it is more dramatic and more thoroughly studied), and to some extent in psychedelic-assisted therapy research.So the dip is not a bug. It is, more often than not, a sign that the network is reorganizing — a small clinical price for the rearrangement that produces the eventual benefit.

The bottom line

If you experience a temporary worsening of mood, energy, or sleep somewhere in the second or third week of your TMS course, the most likely explanation is the TMS dip. It is brief. It resolves. It is often followed by the most noticeable improvement of the entire course. The single most important thing you can do is flag it to your treating clinician and continue with treatment as scheduled.

The exception is new or intensifying suicidal thoughts, which are not the dip and require same-day clinical contact.

If you are weighing TMS as a treatment option, the most useful next step is a structured clinical evaluation with a psychiatrist who works with neuromodulation — both to determine whether TMS is the right protocol for you, and to set realistic expectations for what the course will feel like, dip included.