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Journal of Mood and Anxiety Disorders logoLink to Journal of Mood and Anxiety Disorders
. 2023 Sep 29;3:100028. doi: 10.1016/j.xjmad.2023.100028

Depression and anxiety outcomes of adults undergoing intermittent theta burst stimulation (iTBS) treatment for major depressive disorder: A naturalistic study

Noah A Lee a, Simon Kung b,⁎, Yuliang Hu b, Stacy E Greenwaldt b, Maria I Lapid b, Paul E Croarkin b
PMCID: PMC12243985  PMID: 40655561

Abstract

Background

Standard repetitive transcranial magnetic stimulation (rTMS) and intermittent theta burst stimulation (iTBS) are approved treatments for major depressive disorder (MDD). iTBS offers shorter treatment durations and increased accessibility. This study examines the clinical outcomes of iTBS for MDD in a tertiary medical center.

Methods

Patients who underwent iTBS for MDD at Mayo Clinic Rochester between March 2021 and January 2023 were included. Baseline and endpoint scores of the Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder 7-item (GAD-7) were compared using t-tests. Response, remission, and a single question patient-reported outcome (PRO) of "Did the treatment help?" were reported. Outcomes of patients with anxious depression (GAD-7 ≥10) were also reported.

Results

Forty-two patients (mean age 41.7 years, 59.5% female) were analyzed. iTBS resulted in a significant reduction in depression symptoms (PHQ-9: baseline mean 19.9, endpoint mean 13.0, p < 0.001). The response rate was 38.1%, remission rate was 9.5%, and PRO was 57.1%. Anxiety symptoms also significantly improved (GAD-7: baseline mean 13.0, endpoint mean 9.1, p < 0.001). The response rate for anxiety was 33.3%, and remission rate was 28.6%. Our response rate for depression was comparable to existing literature, while the remission rate was lower.

Conclusion

iTBS demonstrated significant reductions in depression and anxiety symptoms among patients with MDD, and in the subset of patients with anxious depression. The single question PRO can be a practical aid in patient discussions. These findings contribute to the growing body of literature on iTBS for MDD.

Keywords: Major depressive disorder, Anxiety, Repetitive transcranial magnetic stimulation, Intermittent theta burst stimulation, Neuromodulation

Highlights

  • •

    Study reviewed iTBS outcomes for MDD patients, finding a depression response rate of 38.1% and remission rate of 9.5%.

  • •

    iTBS response rate was lower compared to other studies, while remission rate was much lower.

  • •

    Patient-reported outcome question indicated 57.1% improvement, closer to response rates from other studies.

  • •

    iTBS and rTMS showed similar efficacy for depression based on PHQ-9 scores, with no significant differences.

  • •

    Gender and age did not predict treatment outcomes; co-morbid anxiety symptoms improved with iTBS.

1. Introduction

Major depressive disorder (MDD) is one of the most prevalent mental health disorders globally, affecting an estimated 4.4% of the world's population [1]. Anxiety is a common co-occurring symptom in those with MDD and may share a common genetic basis [2]. First-line treatment options for depression and anxiety consist of psychotherapy, including cognitive-behavioral therapy (CBT), interpersonal therapy (IPT), and psychodynamic therapy (PD), and pharmacological treatments such as antidepressants [3].

Despite the availability of these treatments, many patients continue to experience persistent symptoms of depression and anxiety, leading to treatment-resistance. Remission occurred only in 37% of a first trial of an antidepressant, and approximately 30% of patients are considered treatment-resistant with several failed antidepressant trials [4], [5]. This highlights the need for alternative treatments such as repetitive transcranial magmatic stimulation (rTMS).

rTMS involves the application of magnetic fields to the brain to induce electrical currents that stimulate neurons in specific regions. The U.S. Food and Drug Administration (FDA) approved rTMS for major depressive disorder in 2008. A multisite, naturalistic, observational study of 307 outpatients with major depression treated with rTMS found a 56% response rate and 28% remission rate [6]. In a sample of 5010 patients from a large rTMS registry, response rates were noted to be 58–83% and remission rates were 28–62% [7].

One particular type of rTMS that has gained increasing attention in recent years is intermittent theta burst stimulation (iTBS) [8]. Unlike standard rTMS, which is usually delivered at a frequency of 10–20 Hz, iTBS utilizes bursts of 50 Hz. The unique pattern of iTBS has been shown to produce longer-lasting effects on brain activity compared to traditional rTMS, making it a potentially more effective treatment option for depression and anxiety [9], [10]. Another advantage is that iTBS treatments take only 3.5 min compared to 18–37 min with standard rTMS, thus reducing the patient’s time burden and allowing providers to treat more patients. The efficacy of iTBS was found to be similar to rTMS in a randomized non-inferiority trial of 385 patients, subsequently iTBS was FDA-approved for MDD [11]. A systematic review and meta-analysis of randomized controlled trials comprising 667 patients found positive effect of iTBS versus sham, and non-inferiority of iTBS versus standard rTMS [12]. Further studies support that rTMS and iTBS have similar outcomes [13], [14].

While there are many reports of naturalistic patient outcomes with standard rTMS, there are fewer reports of iTBS outcomes [14]. Given that clinical trials of iTBS are limited, naturalistic registry studies will have an important role in refining future practice. In this study, we review the effectiveness of iTBS at our tertiary medical center, and compare it to a previous sample of our patients who received standard rTMS. We also investigate whether the anxiety symptoms which frequently accompany depression improve with iTBS.

2. Materials and methods

This study was approved by the Mayo Clinic Institutional Review Board (IRB). Adult patients who completed the iTBS protocol for MDD at Mayo Clinic in Rochester, Minnesota, between March 16, 2021 and January 18, 2023 were included. The diagnosis of MDD was made clinically using the DSM-5-TR. A diagnosis of GAD was not present in all cases, but we measured anxiety symptoms to examine the efficacy of iTBS with regards to alleviating anxiety.

The NeuroStar (Neuronetics, Malvern, PA) device was used with iTBS parameters of 3 pulses per second, 20 ms interpulse intervals, 5 bursts per second, 2 s stimulation time, 8 s intertrain interval, up to 120% of motor threshold over the left dorsolateral prefrontal cortex (DLPFC) for 600 pulses (3 min 20 s) each session. Up to 30 sessions (5 sessions per week, with patients occasionally missing a treatment due to scheduling or other issues) and 6 taper (two or three times per week) sessions were given. Patients who did not finish at least 20 sessions were excluded. For patients who had more than one series of treatment, only the first series was included.

Patients completed the PHQ-9 and GAD-7 at baseline, approximately every two weeks during treatment, and at the end of the acute treatment. Response (≥50% reduction in PHQ-9 or GAD-7) and remission (PHQ-9 <5, GAD-7 <5) definitions were used. A single question patient-reported outcome (PRO) was recorded as a measure of “meaningful improvement” at the end of their treatment course. It was a yes/no question “Did you feel treatment was helpful?”

Demographic information, PHQ-9 and GAD-7 scores, and response, remission, and meaningful improvement outcome measures were summarized using descriptive statistics. Student’s t-test/Wilcoxon test was used to compare PHQ-9 and GAD-7 at baseline and endpoint. Logistic regression was used to identify predictors (age and gender) for the dichotomous outcomes, including a post-hoc analysis of younger (<60 years) versus older (≥60 years) age groups for comparison with a previous study which used age 60 as the cut-off [9]. The change in PHQ-9 scores and change in GAD-7 scores were correlated using the Pearson correlation coefficient. Using a GAD-7 score of ≥ 10 to define anxious depression, t-tests were used to compare the effects of iTBS on those with and without anxious depression. Jamovi (https://www.jamovi.org, Sydney, Australia) was used for data analysis, and statistical significance was defined as two-tailed p < 0.05 (Table 1, Table 2).

Table 1.

PHQ-9 and GAD-7 mean baseline and endpoint scores, response, and remission rates.

Baseline Endpoint Response (%) Remission (%) Meaningful Improvement
PHQ-9 19.9 (± 3.76) 13.0 (± 6.36) 38.1 9.5 57.1%
GAD-7 13.0 (± 5.22) 9.2 (± 6.39) 33.3 28.6 N/A
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Table 2.

PHQ-9 and GAD-7 outcomes between those with anxious depression and non-anxious depression.

Anxious Depression (n = 31) Non-Anxious Depression (n = 11) Comparison p values
PHQ-9 Outcomes
Baseline PHQ-9 score 20.0 19.4 p > 0.05
Endpoint PHQ-9 score 13.2 12.2 p > 0.05
Difference (pretreatment – posttreatment) 6.8 7.2 p > 0.05
Effect size (d) of PHQ-9 score change 1.1 0.8
Response rate (%) 35.5 45.5 p > 0.05
Remission rate (%) 6.5 18.2 p > 0.05
GAD-7 outcomes
Baseline GAD-7 score 15.5 6.0 p < 0.01*
Endpoint GAD-7 score 10.8 4.8 p < 0.01*
Difference (pretreatment – posttreatment) 4.7 1.2 p > 0.05
Effect size (d) of GAD-7 score change 0.9 0.3
Response rate (%) 35.5 27.3 p > 0.05
Remission rate (%) 25.8 36.4 p > 0.05
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3. Results

Forty-two patients (mean age 41.7 years, 59.5% female) were analyzed. For PHQ-9, the mean baseline score was 19.9 (SD ± 3.8), mean endpoint score was 13.0 (SD ± 6.4), with mean change of 6.9 (SD ± 6.7), p < 0.001. Response rate was 38.1% and remission rate was 9.5%. The rate of positive response from the PRO was 57.1%. For GAD-7, the mean baseline score was 13.0 (SD ± 5.2), mean endpoint was 9.1 (SD ± 6.4), with mean change of 3.7 (SD ± 5.3), p < 0.001. Response rate was 33.3% and remission rate was 28.6%.

Age was not significantly associated with an increased odds for response (OR = 1.032, 95% CI 0.9918–1.07), remission (OR = 0.980, 95% CI 0.9132–1.05), or the PRO (OR = 1.010, 95% CI 0.972–1.05) with regards to depression. Interestingly, age was significantly associated with an increased odds for response (OR = 1.0638, 95% CI 1.01594–1.114) but not remission (OR = 1.029, 95% CI 0.9869–1.073) with regards to anxiety. Adjusting for gender did not change these results.

Post-hoc analysis based on prior literature of outcomes using age 60 as a cut-off by younger (<60 years) and older (≥60 years) age groups did not yield any statistically significant associations with regards to response or remission for both depression and anxiety. These findings persisted after adjusting for gender.

A Pearson correlation coefficient was computed to assess the linear relationship between depression change scores and anxiety change scores. There was a strong positive correlation between the two variables, r(40) = .71, p < .001 (Fig. 1).

Fig. 1.

Fig. 1

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Change in PHQ-9 scores plotted against change in GAD-7 scores.

GAD-7 scores decreased markedly in the anxious depression group, with a GAD-7 response rate of 35.5% and GAD-7 remission rate of 25.8%. GAD-7 scores did not decrease significantly in the non-anxious group. The effect sizes for the decrease in GAD-7 were 0.87 among the anxious depression group and from 0.27 among the non-anxious depression group.

At baseline, the anxious depressed group scored 1.4 points higher on the PHQ-9 than the non-anxious group, and 1.0 points higher at final observation, which was not significant. The effect sizes for the decrease in PHQ-9 were 1.12 among the anxious depression group and 0.82 among the non-anxious depression group. The response and remission rates for the anxious depressed group were 35.5% and 6.5%, respectively whereas the response and remission rates for the non-anxious group were 45.5% and 18.2%, respectively. While the depression response and remission rates were higher in the non-anxious depressed group, the differences were not statistically significant.

4. Discussion

In this naturalistic study, we reviewed our single-site tertiary medical center outcomes of iTBS for patients with MDD and reported depression and anxiety outcomes. We found a depression response rate of 38.1% and remission rate of 9.5%, based on the PHQ-9. Compared to current studies showing response rates ranging between 37% and 59% for iTBS and 31–83% for rTMS, our response rate for iTBS was on the lower range, while our remission rate was much lower compared to current studies showing 16–35% for iTBS and 15–62% for rTMS [13], [14], [15], [16], [17], [18], [19]. Our lower response and remission rates might reflect more treatment resistance.

To assess patient subjective improvement regardless of meeting the formal depression response criteria of ≥ 50% improvement, we used a single patient-reported outcome question used in our previous rTMS study: “Did you feel treatment was helpful?” [13]. Although this question is simplistic, vague, and affected by patient factors such as motivation, expectancy, time investment, and monetary considerations, it leaves the decision of improvement to the patient and not the clinician. This improvement was calculated to be 57.1%, which is closer to the response rates from other studies cited above. This single PRO question may reflect more realistic clinical outcomes.

Our previous naturalistic study using 10 Hz rTMS for depression (n = 84) reported a 42.9% response rate, 16.7% remission rate, and 61.9% positive PRO response [20]. Compared to our current study, these differences in outcomes were not statistically significant. Both studies showed statistically significant decreases in mean PHQ-9 scores (7.94 for rTMS and 6.90 for iTBS), and t-test comparison of the differences between these two change scores were not statistically significant. Therefore, we conclude that iTBS is as efficacious as rTMS at alleviating depression at our site.

Regarding gender and age predictors of outcome, we did not find an association with gender, which differs from other reports that females have better response and remission rates [7]. Age did not predict response, remission, or positive PRO response. These findings are similar to those of a previous study of 231 patients (n = 156, <60 years, and n = 75, ≥60 years) in which both age groups showed significant improvement and there was no difference in response and remission rates between the two groups [21]. Other studies have also found reduced or no impact of older age on therapeutic benefits [7]. This was a post-hoc analysis and thus needs to be interpreted with caution. Furthermore, this is the only study to evaluate age and iTBS response, so more research is needed.

We also examined the impact of co-morbid anxiety symptoms on depression outcomes. Patients with anxious depression (GAD-7 ≥ 10, 74% of our sample) had comparable reductions in PHQ-9 scores compared to those with non-anxious depression. Although the depression response and remission rates were higher in the non-anxious depressed group, the differences were not statistically significant. The effect size of PHQ-9 improvement was larger in the anxious depressed group. As for anxiety symptoms, in the anxious depression group, response rate was 35.5% and remission rate 25.8%, supporting that iTBS also alleviates the anxiety symptoms. The remission rate was higher than we expected, when keeping in mind that anxiety is difficult to treat. The response and remission rates for the non-anxious depressed group cannot be meaningfully interpreted, as those patients were not anxious to begin with, with a baseline mean GAD-7 score of 6.0.

Our findings regarding anxiety were similar to a large industry-sponsored clinical outcomes registry study of 1820 patients with MDD, which showed that rTMS improved both depression and anxiety symptoms. Our baseline mean GAD-7 score of 15.5 in the anxious depressed group was similar to their score of 16.4, and in both studies, the baseline mean GAD-7 score for the non-anxious depressed group was 6.0. In their completer group, the mean GAD-7 improvement was 7.9, larger than our 4.65, and thus their response rate was higher at 54.3% and remission rate 30.6%. However, an important difference is that their outcomes were for rTMS protocols other than specifically iTBS [22]. Other studies have also found co-morbid anxiety symptom improvement in patients with MDD, with both rTMS and iTBS [23], [24]. One study reported an anxiety response rate of 41.5% (higher than our 33.3%) and remission rate of 22.6% (lower than our 28.6%) [24]. Accordingly, the FDA recently approved an indication for rTMS for the reduction of anxiety symptoms in MDD. Note that in these studies, as with ours, patients were treated primarily for depression and not primary anxiety, and anxiety scores were a secondary outcome.

Our study had several limitations. The overall sample size was small. However, we achieved a homogenous group of patients who received a course of left DLPFC iTBS. While most of the patients completed 30 treatments and tolerated 120% of motor threshold, we did not adjust for patients who finished earlier than 30 treatments or were treated at 100–110% of motor threshold. Being that this study was naturalistic and observational, we did not control for concurrent treatments the patient was receiving, although the majority of the patients did not change their concurrent treatments. Naturalistic studies can give us insights into real-world outcomes. We did not ask a single patient-related outcome question with regards to anxiety response as we did with depression, which can succinctly summarize benefit. When comparing our response and remission rates to other studies, we did not specify which rating scale the other studies used – some used other self-rating scales or clinician-rated scales.

5. Conclusions

In conclusion, our naturalistic study found that iTBS improved both depression and anxiety in patients with MDD. The depression response rate was on the lower range for other published iTBS and rTMS studies, and the remission rate was much lower compared to other studies. However, the PRO single question of improvement was more consistent with other publication response rates, and would be a good point of discussion with patients considering iTBS or rTMS. Depression improved regardless of whether patients had high anxiety or not, and patients can also be counseled that the co-morbid anxiety symptoms of depression will improve with iTBS.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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