Li ZY, Zhang YW, Yang HR, Ren YQ, Wu HJ, Zhang MY, Zhang S, Jiao YF, Yu WF, Xiao J, Gao P, Yang H. Comprehensive bibliometric analysis of transcranial magnetic stimulation-based depression treatment from 2003 to 2022: Research hotspots and trends. World J Psychiatry 2025; 15(4): 104600 [DOI: 10.5498/wjp.v15.i4.104600]
Corresponding Author of This Article
Heng Yang, MD, PhD, Professor, Department of Anesthesiology, The Third Affiliated Hospital of Anhui Medical University, No. 390 Huaihe Road, Luyang District, Hefei 230061, Anhui Province, China. yangh999@yeah.net
Research Domain of This Article
Psychiatry
Article-Type of This Article
Scientometrics
Open-Access Policy of This Article
This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Zheng-Yu Li, Yu-Wei Zhang, Hong-Jin Wu, Meng-Yun Zhang, Heng Yang, Department of Anesthesiology, The Third Affiliated Hospital of Anhui Medical University, Hefei 230061, Anhui Province, China
Zheng-Yu Li, Yu-Qing Ren, Song Zhang, Ying-Fu Jiao, Wei-Feng Yu, Jie Xiao, Po Gao, Department of Anesthesiology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
Zheng-Yu Li, Yu-Qing Ren, Song Zhang, Ying-Fu Jiao, Wei-Feng Yu, Jie Xiao, Po Gao, Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai 200127, China
Hao-Ran Yang, School of Educational Sciences, Chongqing Normal University, Chongqing 400030, China
Author contributions: Yang H, Gao P and Xiao J conceptualized and designed the study; Li ZY, Zhang YW, Yang HR and Ren YQ screened the articles, wrote the original manuscript, and performed the CiteSpace and VOSviewer analysis; Yang H, Gao P, Xiao J and Li ZY revised the manuscript; Zhang MY, Wu HJ, Zhang S, Jiao YF and Yu WF critically edited the manuscript; All authors contributed to the article and approved the submitted version.
Supported by the National Natural Science Foundation of China, No. 82270916, No. 81800748 and No. 82371478; and the Third Affiliated Hospital of Anhui Medical University Basic and Clinical Collaborative Research Enhancement Program Cultivation Special Funding Project, No. 2022sfy009.
Conflict-of-interest statement: The authors declare that they have no conflict of interest.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Heng Yang, MD, PhD, Professor, Department of Anesthesiology, The Third Affiliated Hospital of Anhui Medical University, No. 390 Huaihe Road, Luyang District, Hefei 230061, Anhui Province, China. yangh999@yeah.net
Received: December 26, 2024 Revised: February 3, 2025 Accepted: February 25, 2025 Published online: April 19, 2025 Processing time: 89 Days and 18.3 Hours
Abstract
BACKGROUND
Depression has become a global public health problem. In recent years, transcranial magnetic stimulation (TMS) has gained considerable attention as a non-invasive treatment for depression.
AIM
To investigate the research hotspots and trends in the field of TMS-based depression treatment from a bibliometric perspective.
METHODS
Using the Web of Science Core Collection, articles published between 2003 and 2022 on TMS-based depression treatment were retrieved from the science citation index expanded. The publication trends and research hotspots were analyzed using VOSviewer, CiteSpace, and the bibliometric online analysis platform. Regression analysis was performed using Microsoft Excel 2021 to predict publication growth trends.
RESULTS
We identified a total of 702 articles on TMS-based depression treatment with a predominance of clinical studies. Analysis of collaborative networks showed that the United States, the University of Toronto, and Daskalakis ZJ were identified as the most impactful country, institution, and researcher, respectively. In keyword burst analysis, it was found that theta burst stimulation (TBS), functional connectivity, and frequency were the most recent research hotspots.
CONCLUSION
TMS provides a novel therapeutic option for patients with treatment-resistant depression. Neuroimaging technology enables more precise TMS treatment, while the novel TMS modality, TBS, enhances both therapeutic efficacy and patient experience in TMS-based depression treatment. The integration of neuroimaging techniques with TBS represents a promising research direction for advancing TMS-based depression treatment. This study presents systematic information and recommendations to guide future research on TMS-based depression treatment.
Core Tip: This is the first bibliometric analysis of research relating to transcranial magnetic stimulation-based depression treatment in the past decade. Between 2003 and 2022, the United States was the leading country, in both the number of outputs and international collaborations. The University of Toronto and Daskalakis ZJ were the most productive institution and author, respectively. Theta burst stimulation and functional connectivity are current research hotspots.
Citation: Li ZY, Zhang YW, Yang HR, Ren YQ, Wu HJ, Zhang MY, Zhang S, Jiao YF, Yu WF, Xiao J, Gao P, Yang H. Comprehensive bibliometric analysis of transcranial magnetic stimulation-based depression treatment from 2003 to 2022: Research hotspots and trends. World J Psychiatry 2025; 15(4): 104600
Depression is a debilitating disorder that significantly impairs psychosocial functioning and diminishes quality of life[1]. World Health Organization identified major depressive disorder (MDD) as the third largest contributor to global disease burden in 2008, and predicted it would take the top spot by 2030[2]. Various treatment options are accessible for individuals with depression, including a variety of antidepressant medications, several psychotherapies, and electroconvulsive therapy. Despite recent advances in these treatments, approximately 30% of all depression patients still experience ineffective or poor outcomes[3]. Therefore, better treatments would be a benefit to MDD patients from all over the world. As an effective noninvasive treatment for depression, transcranial magnetic stimulation (TMS) is relatively simple to administer and has decreased side effects[4].
TMS is a non-invasive neuromodulation technique that uses a time-varying magnetic field to stimulate the cerebral cortex, generating induced currents that modulate neuronal electrical activity[5]. Repetitive TMS (rTMS), an advanced form of TMS, involves the repeated delivery of high- or low-frequency magnetic pulses to the brain over a sustained period[6]. The Food and Drug Administration (FDA) approved TMS in 2008 for treating MDD clinically[7]. However, owing to individual variability and the challenges associated with precise localization, the neurobiological mechanisms of TMS-based depression treatment have not been fully elucidated, and its optimal stimulation parameters remain undetermined. Although the high worldwide prevalence of depression has led to a growing interest in TMS-based depression treatment among researchers, few articles have summarized current advances in this area and predicted future research focal points.
Bibliometric analysis is a comprehensive and up-to-date econometric study of publications in a defined field of study during a specific time frame. It examines the quantity of articles, authors, countries, regions, journals, and references among other parameters[8-11]. Many research fields in neuropsychiatry have been previously analyzed from a bibliometric standpoint, including depression[12], selective 5-hydroxytryptamine reuptake inhibitors[13], neuroimaging[14], classification/diagnosis of psychiatric disorders[15], and biologic treatments for MDD[16]. Bibliometric analysis not only enables researchers to gain insights into field dynamics and to foster interdisciplinary collaboration, international cooperation, and knowledge innovation, but also support clinicians in staying informed about the latest therapeutic approaches to enhance clinical practice, making it an essential tool in modern scientific research.
In addition, a recent bibliometric analysis was conducted on the 50 most cited articles in studies related to rTMS for the treatment of depression[17]. Unfortunately, the study ultimately analyzed articles covering only the 1993-2012 period. It did not include a comprehensive analysis of articles published over the last ten years, including reference co-citation analysis and keyword burst detection, which included the most recent information. In addition, the data analysis in this study only used the Scopus library database, which may have resulted in an incomplete literature sample. The current study aimed to conduct a bibliometric analysis and summarize original research related to TMS-based depression treatment, published between 2003 and 2022. We analyzed the research trends in this area over the last two decades to identify new findings in neurobiological mechanisms and new advances in stimulation parameters. In this study, we present a panoramic view of research in this field and identify potential hotspots for research.
MATERIALS AND METHODS
Data origins and search approaches
On July 10, 2023, data were extracted from the Web of Science Core Collection (WoSCC) for the period January 1, 2003 to December 31, 2022. Data extraction and downloads were completed within one day to eliminate database update bias. We obtained pertinent articles by employing the following search criteria: TS = [(transcranial magnetic stimulation) OR (theta burst stimulation) OR (TMS) OR (TBS)] AND [TS = (depression) OR (depressive disorder) OR (MDD) OR treatment-resistant depression (TRD)] AND [DT = (article)] AND [LA = (English)]. There was only one source of data, the science citation index-expanded (SCI-E). Exclusion criteria were the following: (1) Studies with no connection to TMS-based depression treatment; (2) Types of documents other than scientific articles (such as proceeding papers, book chapters, reviews, corrections, editorial materials, news items, meeting abstracts, letters, and retracted publications); (3) Non-English language publications, and (4) Duplicate publications. To ensure the precision of bibliometric analysis outcomes, four researchers (Li ZY, Zhang YW, Yang HR and Ren YQ) screened all publications obtained through the search strategy, encompassing titles, author names, abstracts, and publication dates. Then, raw data were downloaded in the form of text files containing the full records. The detailed screening workflow is schematically represented in Figure 1.
Figure 1 Flowchart of the study.
TMS: Transcranial magnetic stimulation; TBS: Theta burst stimulation; MDD: Major depressive disorder; TRD: Treatment-resistant depression.
Bibliometric analysis
To characterize all literature items on TMS-based depression treatment, we used the Web of Science platform (http://wcs.webofknowledge.com) to assess the search results and produce histograms that depict publication trends. The eligible data sourced from WoSCC were converted into TXT format and subsequently imported into VOSviewer 1.6.19 (Leiden University, Leiden, The Netherlands) and CiteSpace V6.1R6 (Drexel University, Philadelphia, Pennsylvania, United States) for analysis. Bibliometric’s online analysis platform (https://bibliometric.com) was also used to analyze the data using its “bibliometrix” R package.
From the WoSCC, we obtained the annual publication count. With the bibliometric analysis platform, we exported the number of publications from the top 10 countries/regions, the top 10 most active journals, and the top 100 most frequently used keywords. Furthermore, collaborative research between countries/regions as well as between authors was explored in the study by utilizing VOSviewer software, a tool for constructing visual bibliometric maps[18]. CiteSpace stands out as the predominant and widely recognized bibliometric visualization tool[19] for outputting a variety of data to aid in comprehending the current state of research on TMS-based depression treatment, and to forecast potential focal points in this area. For this research, the parameters utilized in CiteSpace included a time frame of 2003-2022, one year per slice, all terms selected as sources, one node type selected at a time, pathfinder for pruning, and clustering view-static for visualization with merged networks displayed.
RESULTS
Analysis of the number and trend of publications
A total of 702 articles meeting our inclusion criteria were retrieved. As depicted in Figure 2A, according to publication numbers, research related to TMS-based depression treatment can be broadly divided into two periods. Compared to the previous period (2003-2017), the number of publications in the last five years (2018-2022) shows a marked increase. This trend suggests that the global interest in research on TMS-based depression treatment has been increasing. We additionally tallied the quantity of clinical and basic research articles, which revealed that clinical research had contributed the most to publications over the past twenty years (Figure 2B). Moreover, Microsoft Excel 2021 was utilized for modeling the growth trend, as follows: F (x) = 0.229 x2 - 918.33 x + 920762 (R2 = 0.9158), predicting that about 156 articles will be published in 2030 (Supplementary Figure 1).
Figure 2 Analysis of the number and trend of publications on transcranial magnetic stimulation-based depression treatment, from 2003 to 2022.
A: Annual number of papers in the transcranial magnetic stimulation (TMS)-based depression treatment field, published from 2003 to 2022, obtained from Web of Science data; B: The ratio of basic and clinical research articles on TMS-based depression treatment published from 2003 to 2022; C: The publication counts and growth patterns of the leading 10 countries/regions in the TMS-based depression treatment field; D: Total citations from 702 articles retrieved across various countries. The ten countries with the most citations are shown.
To determine the primary contributor in TMS-based depression treatment research over the past two decades, we utilized an online bibliometric analysis platform (http://bibliometric.com) to quantify the publication output across various countries/regions. In Figure 2C, the bar chart represents the top 10 most prolific countries in the past 20 years. The United States has maintained its dominant position in the TMS-based depression treatment field, while China has come in second place for the number of papers published since 2020.
As part of our investigation, we examined the overall citation counts for articles from various countries and regions, ultimately compiling a list of the top 10 countries and regions with the highest citation numbers (Figure 2D). During this 20-year period, the United States ranked first with 9298 total citations for all relevant papers published. Australia and Canada held the second and third positions, with 2580 and 2480 citations, respectively. By dividing the total number of citations by the total number of articles, we can calculate the average number of citations for articles. The top 10 countries/regions, ranked by the average number of citations, are detailed in Table 1. According to average number of citations, the United States (56.00), Israel (51.10), and Belgium (42.51) are the top three countries. These findings highlight the substantial contributions of the United States to the field through the execution of numerous high-quality studies, thereby reinforcing its position as a global leader in advancing research on TMS-based depression treatment.
Table 1 The top 10 countries with the highest total citations in the transcranial magnetic stimulation-based depression treatment field from 2003 to 2022 (arranged by the average citation count).
Rank
Country
Number of publications
Total number of citations
Average number of citations
1
United States
166
9298
56.00
2
Israel
23
1176
51.10
3
Belgium
22
935
42.50
4
Germany
32
1347
42.10
5
Australia
63
2580
41.00
6
Italy
26
1053
40.50
7
Canada
71
2480
34.90
8
Japan
30
762
25.40
9
France
36
899
25.00
10
China
86
1459
17.00
Analysis of collaborations among countries/regions and among institutions
There have been 702 original articles on TMS-based depression treatment published in 39 countries and regions over the past two decades. Utilizing the VOSviewer software, an analysis was conducted to explore the collaborative status among these countries and regions. Figure 3A shows academic collaborations among countries/regions in the TMS-based depression treatment research field. The level of collaborations between countries/regions is shown by the thickness of the connecting lines. Results show that the United States participates most extensively in international cooperation. Furthermore, among the countries and regions, Canada and Australia collaborated most frequently, followed by Canada and the United States.
Figure 3 Map of national/regional and institutional cooperation networks in the transcranial magnetic stimulation-based depression treatment field.
A: Collaborations among 39 countries/regions in the transcranial magnetic stimulation (TMS)-based depression treatment research field; B: Collaborative network mapping of institutions engaged in TMS-based depression treatment research field. The institutions with the highest productivity are presented.
To understand the collaboration status among these institutions, the data in TXT format was imported into the CiteSpace software. A total of 438 research institutions participated in the TMS-based depression treatment field. In Figure 3B, the visualization mapping presents the top 10 highest productive institutions. Various institutions have published different numbers of articles, while the thickness of the connecting lines indicates the degree of collaboration between them. There were eight productive institutions with more than 20 publications. The University of Toronto (Toronto, ON, Canada) published the largest number of articles (67). Among the ten most productive institutions, four were Canadian, while three were American, underscoring the significant academic influence of research institutions from both countries in this field of study.
Analysis of co-authorship networks and distribution of core authors
The outcome of a study is typically a product of the joint efforts of multiple researchers. Through the analysis of author collaboration networks within a particular field, the core authors and the level of collaboration among them can be identified[20]. In the last two decades, a total of 583 authors have collectively contributed to 702 identified articles. Figure 4 illustrates author collaboration by showcasing the 28 authors with the most publications. The visualization map provides intuitive information about the collaboration between different authors, thus helping researchers identify potential partners. The most articles were contributed by Daskalakis ZJ (61 articles), of the University of California, San Diego School of Medicine (La Jolla, CA, United States), followed by Blumberger DM (46 articles), from the Centre for Addiction and Psychology at the University of Toronto (Toronto, ON, Canada). The author collaboration network map shows strong collaboration between these prolific authors and other authors.
Figure 4 Collaborative network of authors in the transcranial magnetic stimulation-based depression treatment field.
The 28 authors who have the most publications (number of publications ≥ 10) are shown.
Journal analysis
To evaluate journals’ impact, the bibliometrics online analysis platform was utilized. Here, we found that the 702 original papers were published in 571 academic journals. Table 2 displays the top 10 most cited journals, with articles published in Biological Psychiatry being the most cited (3595 citations), followed by Brain Stimulation (2392 citations), Journal of Affective Disorders (2209 citations), Depression and Anxiety (1167 citations), Journal of Clinical Psychiatry (790 citations), Psychiatry Research (751 citations), Journal of ECT (604 citations), International Journal of Neuropsychopharmacology (501 citations), World Journal of Biological Psychiatry (496 citations), and Clinical Neurophysiology (432 citations). The publishers of five journals were based in the United States, whereas the others were in the Netherlands, the United Kingdom, and Ireland. In Biological Psychiatry, the articles had the highest average number of citations (256.8 citations). These findings underscore the substantial academic influence and exceptional quality of this well-established and globally renowned journal.
Table 2 The top 10 most cited journals in the field of transcranial magnetic stimulation-based depression treatment, covering the period from 2003 to 2022 (ranked by total number of citations).
Rank
Journal title
Frequency
Total citations
Average citation per paper
IF (2023)
Country
JCR
1
Biological Psychiatry
14
3595
256.8
9.6
United States
Q1
2
Brain Stimulation
66
2392
36.2
7.6
United States
Q1
3
Journal of Affective Disorders
78
2209
28.3
4.9
Netherlands
Q1
4
Depression and Anxiety
21
1167
55.6
4.7
United States
Q1
5
Journal of Clinical Psychiatry
12
790
65.8
4.5
United States
Q1
6
Psychiatry Research
33
751
22.8
4.2
Netherlands
Q1
7
Journal of ECT
30
604
20.1
1.8
United States
Q3
8
International Journal of Neuropsychopharmacology
14
501
35.8
4.5
England
Q1
9
World Journal of Biological Psychiatry
13
496
38.2
3.0
England
Q2
10
Clinical Neurophysiology
9
432
48.0
3.7
Ireland
Q1
Co-citation analysis and clustered networks
In Figure 5A, each node signifies a reference, with connecting lines indicating that these articles were cited by the same article among the 702 articles. The larger the node, the higher the frequency of citations. Thicker connecting lines between nodes imply a higher co-citation intensity. In addition, the presence of red nodes suggests that the document has received frequent citations in recent years, while gray nodes indicate citations from earlier years. Citations serve as an important metric for measuring an article’s influence within a particular field of study. Table 3 displays the top 10 most cited articles out of a total of 702 articles. In 2007, an article published in Biological Psychiatry by O’Reardon et al[21] ranked first in citations (1092 citations) for a multicenter, randomized controlled trial, demonstrating that TMS of the left dorsolateral prefrontal cortex (DLPFC) was effective in treating major depression, with minimal side effects. The second- and third-ranked articles were published in Archives of General Psychiatry and Biological Psychiatry and were cited 652 and 584 times, respectively. The former demonstrated that daily left prefrontal rTMS could safely and effectively treat MDD[22], while the latter confirmed that different TMS targets lead to differences in the efficacy of TMS-based depression treatment[23].
Figure 5 Analysis of the reference co-citation network in publications on transcranial magnetic stimulation-based depression treatment from 2003 to 2022.
A: A co-citation map generated by CiteSpace illustrates 12940 references related to research on transcranial magnetic stimulation (TMS)-based depression treatment. The top ten most cited publications are presented along with the year of publication and the first author; B: Top 25 references with highest citation bursts in articles on TMS-based depression treatment, published between 2003 and 2022. The red bars signify citation bursts.
Table 3 The top 10 highly-cited references among 702 retrieved articles on transcranial magnetic stimulation-based depression treatment research, published from 2003 to 2022 (sorted by citation frequency).
Rank
Title
First author
Source
Year
Cited frequency
DOI
1
Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial
O’Reardon JP
Biol Psychiatry
2007
1092
10.1016/j.biopsych.2007.01.018
2
Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder: a sham-controlled randomized trial
George MS
Arch Gen Psychiatry
2010
652
10.1001/archgenpsychiatry.2010.46
3
Efficacy of transcranial magnetic stimulation targets for depression is related to intrinsic functional connectivity with the subgenual cingulate
Fox MD
Biol Psychiatry
2012
584
10.1016/j.biopsych.2012.04.028
4
Effectiveness of theta burst vs high-frequency repetitive transcranial magnetic stimulation in patients with depression (THREE-D): A randomized non-inferiority trial
Blumberger DM
Lancet
2018
464
10.1016/S0140-6736(18)30295-2
5
Default mode network mechanisms of transcranial magnetic stimulation in depression
Liston C
Biol Psychiatry
2014
371
10.1016/j.biopsych.2014.01.023
6
Transcranial magnetic stimulation in the treatment of depression: a double-blind, placebo-controlled trial
Fitzgerald PB
Arch Gen Psychiatry
2003
328
10.1001/archpsyc.60.9.1002
7
A randomized, controlled trial of sequential bilateral repetitive transcranial magnetic stimulation for treatment-resistant depression
Fitzgerald PB
Am J Psychiatry
2006
255
10.1176/appi.ajp.163.1.88
8
Priming stimulation enhances the depressant effect of low-frequency repetitive transcranial magnetic stimulation
Iyer MB
J Neurosci
2003
254
10.1523/JNEUROSCI.23-34-10867.2003
9
A randomized trial of rTMS targeted with MRI based neuro-navigation in treatment-resistant depression
Fitzgerald PB
Neuropsychopharmacology
2009
232
10.1038/npp.2008.233
10
Efficacy and safety of deep transcranial magnetic stimulation for major depression: a prospective multicenter randomized controlled trial
Levkovitz Y
World Psychiatry
2015
222
10.1002/wps.20199
Often, citation bursts of references indicate the emergence or development of a specific field of research based on the rapid increase in citation rates. As depicted in Figure 5B, the top 25 references exhibiting the most notable citation bursts over the last two decades were identified through the utilization of CiteSpace. Blue represents 2003-2022, while red represents the period when burst references were upheld. The most recent and most cited study was a randomized, multicenter, non-inferiority study, published in Lancet in 2018. A total of 414 patients diagnosed with refractory major depression were included. This study concluded that intermittent theta burst stimulation (TBS) was no less effective than 10hz rTMS for treating depression. Furthermore, the number of patients treated per day could be increased by a factor of several times, using the current rTMS device[24].
Of 702 articles were analyzed using CiteSpace for co-citation cluster mapping. As depicted in Figure 6A, the hierarchical cluster analysis of co-citations revealed the predominant terms within the realm of TMS-based depression treatment research, including 0, add-on repetitive transcranial magnetic (rtm), 1, high frequency-rtm stimulation (hf-rtms) treatment, 2, right low frequency rtm, 3, treatment outcome, 4, multisite naturalistic, 5, acute treatment, 6, treatment-resistant MDD, 7, randomized controlled study, 8, no-go task, and 9, clinical outcome. The clusters are summarized in Table 4, with a silhouette value above 0.5 demonstrating the validity of the clustering results. These key terms, identified through hierarchical cluster analysis, elucidate the diverse research types, principal research subjects, and TMS therapeutic modalities employed in studies on TMS-based depression treatments.
Figure 6 Clustered network analysis of transcranial magnetic stimulation-based depression treatment publications, covering the period from 2003 to 2022.
A: Co-cited clustering analysis using CiteSpace. Here are the top 10 citation clusters; B: Timeline depicting co-cited references on transcranial magnetic stimulation-based depression treatment.
Table 4 A summary of 10 clusters of the references in publications of transcranial magnetic stimulation-based depression treatment.
Figure 6B shows a timeline perspective to illustrate the shifts in research focal points related to TMS-based depression treatment over the last two decades. Each circle corresponds to a highly cited paper within a distinct cluster, with the size of the tree ring denoting the frequency of citations. Large nodes are frequently cited or saw a sudden spike in citations during a defined period. The co-cited literature clustering with the keyword “hf-rtms treatment” occurred from 2005 to 2013. Recent hotspots are “right low frequency rtm” and “treatment outcome”, which emerged in 2013 and have continued ever since. The focal point of research in this field appears to have transitioned from hf-rtms treatment to right low frequency rtm.
In Figure 7A, the word cloud displays the top 100 most frequently used keywords in TMS-based depression treatment research. There is a positive correlation between the frequency of use and the font size. After excluding the keywords with minor practical significance, the following keywords with high frequency were included: Major depression, TMS, rtms, prefrontal cortex, and dorsolateral prefrontal cortex. The method of keyword burst detection assists in rapidly identifying research hotspots. Figure 7B shows the top 15 strongest keywords for the 2003-2022 keywords bursts. The green line indicates the 2003-2022 period, whereas the red line signifies the timeframe associated with the burst keyword. Among the confirmed keyword bursts, the keywords that highlight persistence through the end of 2022 were “theta burst stimulation” (4.3653), “functional connectivity” (4.2800), and “frequency” (3.9365). The keywords “theta burst stimulation” and “frequency” suggest that the optimal treatment regimen for TMS-based depression treatment continues to be a hot topic in this research field. Furthermore, TBS is a new mode of TMS stimulation that has been recently extensively studied. “Functional connectivity” suggests that researchers have begun to utilize neuroimaging techniques to further investigate the neurobiological mechanisms of TMS-based depression treatment.
Figure 7 Analysis of keywords and detection of bursts in publications on transcranial magnetic stimulation-based depression treatment published between 2003 and 2022.
A: A word cloud of 100 most frequently used keywords associated with depression treatment based on transcranial magnetic stimulation; B: Citation bursts for the top 15 keywords in chronological order, based on their starting years.
DISCUSSION
This study provides the first comprehensive overview of articles in the TMS-based depression treatment field, published over the past 20 years. We expect that this bibliometric analysis will provide valuable insights for policymakers to develop more targeted research funding and healthcare policies, assist researchers in the field of TMS-based depression treatment in identifying promising research directions, and support clinicians in staying informed about the latest therapeutic approaches to enhance clinical practice.
Over the past two decades, the United States, Canada, and China have been major contributors to the TMS-based depression treatment field. The United States has consistently ranked first in the number of publications, number of article citations, average number of citations, and international collaborations. Three of the top ten research organizations with the highest outputs are from the United States, as well as the researcher with the highest number of publications. Five of the ten most active academic journals in the field are from the United States, as well as the most cited journal and article. All of the above findings indicate that the United States has absolute academic influence and dominance in this field, which is inextricably linked to its strong scientific research base, sound regulatory system and adequate financial support. China began to publish research papers in this field in 2011, and the number of published papers has soared in the past five years, surpassing Canada in 2020 and taking the second place; however, the average number of citations (10th place) is clearly lower than that of Canada (2nd place). This shows that China’s academic influence in this field needs to be further improved, especially in terms of high-quality research results.
With the globalization process, there has been an important trend towards greater international collaboration, which has contributed to the production of high-quality research results on public health issues. Among all collaborations, Canada collaborates most closely with Australia, followed by Canada and the United States. In addition, Canadian and American research organizations produced the most publications. These results suggest that international collaborations may underpin the emergence of the United States and Canada as centers of academic activity in the field of TMS-based depression treatment and play a critical role in advancing the field of TMS-based depression treatment. In conclusion, in the face of the global disease burden of depression, research in this area requires more collaboration among countries and institutions.
The recent surge in publications over the last five years indicates that the field of TMS-based depression treatment has received greater attention. In recent years, some clinical studies have combined neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), to observe the functional connectivity between stimulation targets and depression-related brain regions[25-27]. In addition, a variety of new and more optimized TMS treatment modalities have been derived, including TBS[24,28] and accelerated rTMS (arTMS)[29,30]. The continuous improvement of TMS treatment modalities enhances both treatment effectiveness and patient experience. Additionally, the integration with neuroimaging technology enables more precise TMS treatment. Basic experiments are more conducive to exploring the neural mechanisms of TMS for the treatment of depression[31,32]. However, they are limited by the development of TMS devices suitable for small animals, as a result, basic research makes up only a very small portion of research in this area.
The top two authors in the TMS-based depression treatment field are Daskalakis ZJ (61 articles) and Blumberger DM (46 articles), both dedicated to applied research on the use of brain stimulation methods for the treatment of refractory psychiatric disorders, including depression. As Chair of the Department of Psychiatry at the University of California, San Diego School of Medicine, Dr. Daskalakis’ research group focuses on applied research on TMS-based depression treatment of patients with refractory schizophrenia, suicidal ideation, and obsessive-compulsive disorders[33]. Blumberger DM is the Head of the General Adult Psychiatry and Health System at the Canadian Center for Addiction and Mental Health. His primary research interests are clinical intervention trials of new therapies, as well as understanding the neurophysiology of refractory depression across the lifespan[34].
Major research trends can be identified through the application of co-citation cluster analysis. Using a timeline view of the changes in research fields, we found that the latest research trends in the TMS-based depression treatment field include right low frequency rtm and treatment outcome, as shown by the red nodes in Figure 6B. The hf-rtms treatment cluster started to appear in 2005 and ceased to be a hot research topic by 2013. This shift was dictated by the development of TMS-based depression treatment, with the earliest studies using TMS for the treatment of depression employing a single pulse, usually at the cranial apex, with minimal therapeutic benefit[35]. With the observation that patients with clinical MDD showed reduced resting activity of the DLPFC on positron emission tomography imaging, studies of high-frequency rTMS targeting the DLPFC for the treatment of depression began to emerge. Its antidepressant efficacy demonstrated considerable promise[36,37]. In recent years, based on the observation that MDDs may involve hyperactivity in the right prefrontal cortex[38], initial trials of low-frequency right rTMS confirmed its efficacy in samples of non-treatment-resistant patients[39,40].
Keyword bursts are indicators of important research hotspots or emerging trends. The top 15 most cited keyword bursts are listed in Figure 7B. The period of the listed keyword bursts is scattered, but completely covers the 2003-2022 period, indicating that major research interests have evolved over time. Among the three keywords whose outbursts lasted until the end of 2022, the outburst of “theta burst stimulation” began in 2019 and ranked first, with an intensity of 4.3653. Numerous clinical trials and research studies have demonstrated the efficacy and safety of TBS in the treatment of depression, particularly for patients who have not responded to conventional therapies[24,41]. Supported by this robust evidence, the FDA approved TBS for the treatment of depression in 2018. In addition to TBS, arTMS, as another magnetic stimulation modality derived in recent years[42], could also significantly improve patients’ depressive symptoms[30]. Second, the burst of “functional connectivity” stems from the fact that, in recent years, neuroimaging techniques have been introduced into the TMS-based depression treatment field. The most common stimulation site for the treatment of depression is DLPFC. It is usually stimulated with high-frequency stimuli applied to the left side (HFL), and low-frequency stimuli given to the right[43]. Recent studies have found that the left and right prefrontal cortex had functional connectivity with the subgenual anterior cingulate cortex and the posterior cingulate cortex, respectively, which provides a new rationale for the choice of the stimulation site[27]. Furthermore, measurements of neural network functional connectivity by fMRI could predict and track clinical outcomes and optimize the treatment[25]. In addition, MRI-based neuronavigation techniques allow increased accuracy in the localization of the stimulation site and an improved rTMS efficacy[26]. The third keyword burst is “frequency”. Neurophysiological studies have shown that low-frequency rTMS could lead to a transient reduction in local cortical activity, and that high-frequency rTMS increased the excitability of local cortical nerve cells[44]. From the earliest studies of high-frequency rTMS for depression treatment targeting the DLPFC[37], to the later preliminary trials of low-frequency right side rTMS[38], and to the newly derived comparative studies of stimulation modalities with the most commonly used HFL[41], “frequency” has been used throughout almost the entire development of the TMS-based depression treatment field. To sum up, neuroimaging technology facilitates more precise targeting in TMS therapy, while the novel TMS modality, TBS, significantly improves both therapeutic outcomes and patient experience in the treatment of depression. These keywords suggest that TBS, which relies on neuroimaging to navigate precise localizations, may become a promising alternative to antidepressant treatments in the future.
We have several limitations in this study. First, only the data extracted from WoSCC possessed the comprehensive information required for co-citation analysis using CiteSpace. The data extracted from WoSCC encompassed detailed records, including titles, authors, affiliations, and references, all of which are essential for conducting bibliometric analysis. Hence, the data analysis was conducted solely using the WoSCC SCI-E database, thereby excluding records from other prominent search engines such as PubMed, EMBASE, and Ovid. This choice may have resulted in an incomplete literature sample on TMS-based depression treatment studies published over the past 20 years. Second, we excluded articles published in other languages because English is still the preferred language in academic journals today. Third, high-quality studies published recently may not yet have garnered sufficient attention due to citation lag, highlighting the need for updating in future research. Furthermore, despite the increased number of articles published in the TMS-based depression treatment field in recent years, the total number of articles remains relatively small. Thus, the outcomes of our analysis, drawn from the available literature, might be somewhat biased. It is imperative for future research to steer clear of such limitations.
CONCLUSION
In summary, with the help of bibliometric tools, studies on TMS-based depression treatment, published over the last 20 years, have been analyzed. The number of papers has rapidly grown since 2018. The United States and Canada have made the most relevant contributions to this field and are leaders in international collaborations. TMS demonstrates significant efficacy in treating depression, particularly for patients with treatment-resistant depression, offering a novel therapeutic option for this population. Neuroimaging technology enables more precise TMS treatment, while the novel TMS modality, TBS, enhances both therapeutic efficacy and patient experience in TMS-based depression treatment. As a current research hotspot, theta burst stimulation, combined with neuroimaging techniques, may become a promising alternative antidepressant treatment in the future. The present study provides direction guidance for the next steps in investigating the therapeutic parameters and neurobiological mechanisms of TMS-based depression treatment.
Footnotes
Provenance and peer review: Unsolicited article; Externally peer reviewed.
Peer-review model: Single blind
Specialty type: Psychiatry
Country of origin: China
Peer-review report’s classification
Scientific Quality: Grade A, Grade C, Grade C, Grade C
Novelty: Grade A, Grade B, Grade C, Grade C
Creativity or Innovation: Grade A, Grade B, Grade C, Grade C
Scientific Significance: Grade A, Grade B, Grade C, Grade C
P-Reviewer: Li JY; Li Z; Liu YX S-Editor: Fan M L-Editor: A P-Editor: Zhao YQ
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