The Association Between Depression and Tourette Syndrome: A Bibliometric Analysis of Research Hotspots and Emerging Trends from 2001 to 2025

Abstract

Background

Depression is a clinically relevant comorbidity of Tourette syndrome (TS), yet the organization and development of research on this topic remain poorly characterized. This study aimed to map the knowledge structure, research hotspots, and emerging trends in the literature on TS and depression. It also sought to identify questions that warrant further investigation.

Methods

English-language articles and reviews published from 2001 to 2025 were retrieved from the Web of Science Core Collection and Scopus. Bibliometrix, VOSviewer, and CiteSpace were used to analyze publication and citation trends, collaboration networks, co-cited references, keyword co-occurrence, and temporal patterns. A narrative comparison of selected clinical studies informed the interpretation of these findings.

Results

After database-specific screening, 3024 records were combined, and 2311 publications remained after duplicate removal. Publication output increased overall, with the United States, the United Kingdom, and China contributing the most publications. Research themes expanded from tic control and pharmacological treatment to psychiatric comorbidities, mental health, quality of life, and functional outcomes. TS, tic disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, depression, comorbidity, and neuromodulation formed the core keyword network.

Conclusion

Research on TS and depression increasingly addresses psychiatric comorbidity and functional outcomes. These findings support assessing depressive symptoms alongside tic severity and including depression and functional outcomes in future TS research.

Introduction

Tourette Syndrome (TS) is a childhood-onset neurodevelopmental disorder characterized mainly by sudden, rapid, recurrent, and non-rhythmic motor and vocal tics.^1–3 The clinical course of TS is markedly fluctuating; symptoms usually appear in childhood and may gradually lessen with age.^4,5 However, the clinical burden of TS is not limited to tics themselves. Many patients also present with psychiatric comorbidities, including attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), anxiety, depression, sleep disturbances, rage attacks, and autism spectrum disorder.^6–8 These comorbidities not only increase the heterogeneity of the disease but may also have more persistent effects on learning, social interaction, family functioning, and quality of life. In some cases, their clinical burden may even exceed that caused by tic symptoms.^9,10

Depression occurs alongside ADHD, OCD, and anxiety in patients with TS, but its relationships with these conditions are not uniform. A large diagnostic study linked mood disorders in TS to co-occurring OCD.¹¹ A pediatric clinical study, however, found that obsessive-compulsive symptom severity did not distinguish depressed from non-depressed patients.¹² These differences call for closer examination of depression’s clinical correlates and contribution to impairment, beyond its relative frequency among comorbidities.

Depression also warrants attention because of its association with symptoms and everyday functioning. Controlled research in adults has documented elevated depressive symptoms in TS, while adolescent research has linked anxiety-depression symptoms to poorer quality of life.^13,14 Diagnosed depressive disorders and elevated symptom scores describe different outcomes and require separate interpretation. Considering depression alongside other comorbidities can clarify these findings and identify outcomes that matter beyond tic severity.

Clinical studies address specific questions about psychiatric comorbidity, depressive symptoms, and functional outcomes. Bibliometric analysis complements these studies by examining how research is organized and how its themes change over time. Publication counts, citation patterns, and keyword networks locate concentrations of research activity. Interpreting these patterns alongside clinical findings helps distinguish growing interest in a topic from stronger evidence for a clinical explanation or intervention.

Against this background, this study aimed to characterize the knowledge structure, major research themes, and evolving directions of research on depression in Tourette syndrome. It further sought to identify unresolved questions relevant to psychiatric comorbidity and clinical assessment.

Methods

Data Sources and Search Strategy

To systematically examine the developmental trajectory, research hotspots, and future trends of studies related to depression and Tourette Syndrome, this study selected two major literature databases, Web of Science Core Collection (WOSCC) and Scopus, as data sources. Both databases provide relatively complete bibliographic information, author details, institutional affiliations, keywords, abstracts, and reference data, making them suitable for bibliometric analysis. The combined use of these two databases can, to some extent, reduce the omission of relevant publications caused by relying on a single database and thereby improve the comprehensiveness of the results.

The search period was set from January 1, 2001, to December 31, 2025. The search strategy was built around two core concepts: Tourette Syndrome and depression. Search terms related to Tourette Syndrome included “Tourette syndrome”, “Tourette disorder”, “Gilles de la Tourette syndrome”, “tic disorder”, “tics”, “motor tics”, and “vocal tics.” Search terms related to depression included “depression”, “depressive disorder”, “depressive symptoms”, “major depressive disorder”, and “MDD.” These terms were combined using Boolean logic to cover, as comprehensively as possible, clinical, psychiatric, neurodevelopmental, and treatment-related studies concerning the association between depression and Tourette Syndrome.

The inclusion criteria were original research articles and reviews published in English between 2001 and 2025. Other non-research publications were excluded. In addition, records whose titles and abstracts were not directly related to the topic of this study were also removed. Finally, Bibliometrix was used to merge and deduplicate the records retrieved from the two databases.

Data Analysis and Visualization

Data processing and analysis were conducted using Bibliometrix version 5.4.1 in R version 4.5.2, VOSviewer version 1.6.20, and CiteSpace version 7.0.R1. Bibliometrix was used to merge and deduplicate records and summarize publication output, citation indicators, and publication patterns by country and institution.¹⁵ VOSviewer was used to construct collaboration networks for countries, institutions, and authors, together with keyword co-occurrence networks.¹⁶ CiteSpace was used for co-cited reference burst analysis, keyword burst detection, keyword clustering, and timeline analysis.¹⁷

Descriptive analyses summarized publication output, keyword frequencies, country publication shares, and citation indicators. Country publication shares were expressed as percentages of the included publications. Citation indicators comprised total citations and average citation frequency, as reported in the Results. Single-country publications (SCP) and multiple-country publications (MCP) were reported for each country. The international collaboration rate was calculated as MCP/(SCP + MCP) multiplied by 100%. Network relationships were summarized by link strength and total link strength (TLS). TLS is the sum of the strengths of an item’s links to other items. Annual publication counts from 2001 to 2025 were smoothed using locally estimated scatterplot smoothing (LOESS) with a span of 0.40. The curve was generated from the annual counts using the MATLAB smooth function with the “loess” option. Keyword co-occurrence, clustering, thematic evolution, and burst analyses described relationships between topics and changes in research attention.

Before keyword analysis, synonyms and related terms were harmonized to reduce variation in bibliographic terminology. “Tourette’s syndrome”, “Gilles de la Tourette syndrome”, “Tourette disorder”, and “TS” were merged into “Tourette syndrome.” The terms “tic”, “tics”, “motor tics”, “vocal tics”, and “phonic tics” were merged into “Tics.” The terms “tic disorder”, “chronic tic disorder”, and “persistent tic disorder” were merged into “Tic disorders.” The terms “depressive symptoms”, “depressive disorder”, and “depression” were merged into “Depression.” The terms “MDD”, “major depression”, and “major depressive disorder” were merged into “Major depressive disorder.” The terms “ADHD” and “attention deficit hyperactivity disorder” were merged into “Attention-deficit/hyperactivity disorder.” These groupings harmonized bibliographic terms without treating symptom measures and diagnostic categories as clinically equivalent.

We compared selected clinical studies to interpret the bibliometric findings in the Discussion. This narrative comparison covered psychiatric comorbidity, depression risk, depressive symptom profiles, and quality of life in TS. It considered each study’s population, design, principal findings, and limits to clinical interpretation. The comparison supplemented the bibliometric analysis without changing the dataset; it was neither an exhaustive systematic review nor a quantitative synthesis of clinical outcomes.

Results

As shown in Figure 1, the initial search of the WOSCC yielded 1024 records. After excluding 42 records that did not meet the document-type criteria, 38 non-English records, and 31 records not directly related to the topic, 913 publications were retained for the merging stage. The initial search of Scopus yielded 2864 records. After excluding 442 records that did not meet the document-type criteria, 175 non-English records, and 115 irrelevant records, 2111 publications were retained for the merging stage. A total of 3024 records from the two databases were imported into Bibliometrix for duplicate detection. After removing 713 duplicate records, 2311 publications were finally included for subsequent analysis.

Figure 1.

Literature screening and selection process in research.

Annual Trends in Publication Output and Citation Frequency

A total of 2311 publications related to depression and Tourette syndrome were ultimately included in this study, covering the period from 2001 to 2025. These publications provide a relatively comprehensive overview of the development of this field over the past 25 years. Figure 2 shows the annual publication output and average citation frequency in this field from 2001 to 2025. Overall, the annual number of publications showed a gradual upward trend, although the increase was not completely linear. The period from 2001 to 2005 represented the early exploratory stage of the field, with a relatively small number of annual publications, ranging from approximately 30 to 58 articles per year. This suggests that, during this period, the relationship between depression and Tourette syndrome had not yet become an independent and stable research focus.

Figure 2.

Annual trends in publication volume and citation frequency.

From 2006 to 2013, related research entered a more active growth stage. The number of publications increased from 78 in 2006 to 118 in 2013, indicating that researchers had begun to pay greater attention to psychiatric comorbidities in patients with Tourette syndrome. During this stage, the research focus gradually expanded from the simple description of tic symptoms to emotional, behavioral, and neurodevelopmental issues. After 2014, although the annual publication output fluctuated, it generally remained at a relatively high level. In most years, the number of publications approached or exceeded 90, with more marked increases in 2021, 2022, and 2025. Among these years, publication output peaked in 2022, with 148 articles, and remained high in 2025, with 146 articles. These findings indicate that research on the association between depression and Tourette syndrome has developed into a relatively stable research direction and has continued to receive academic attention.

Compared with publication output, the average citation frequency showed a different pattern. As shown by the citation curve in Figure 2, the average citation frequency of publications from the early and middle periods gradually increased and reached a relatively high level around 2019. The decline in average citation frequency in recent years does not necessarily indicate a decrease in research impact; rather, it is more likely due to the limited time available for recently published studies to accumulate citations. This is a common “citation lag” phenomenon in bibliometric analysis.

Figure 3 presents the annual publication counts and the LOESS-smoothed trend from 2001 to 2025. The smoothed curve indicates an overall increase in publication output, with a renewed rise after 2019.

Figure 3.

Trends in the growth of annual publications in the field.

Country/Region and Institutional Collaboration Analysis

Table 1 lists the top 10 countries and institutions by publication output in this field, and Figure 4 presents the collaboration network of major countries and regions. At the country level, the United States was the leading contributor, accounting for 31.50% of total publications, far exceeding all other countries. The United Kingdom ranked second, accounting for 8.26%, followed by China, Canada, Germany, and Italy, with publication shares of 6.71%, 5.54%, 5.28%, and 5.28%, respectively. These results indicate that research on depression and Tourette syndrome has been mainly driven by North American and European countries, with the United States holding a clear advantage in overall output.

Table 1.

Top10 Countries and Institutions in Research

Rank	Country	Articles %	SCP	MCP	MCP %	Affiliation (Country)	Occurrences %
1	USA	31.50	670	58	7.97	UNIVERSITY OF LONDON (UK)	189 (8.18%)
2	UK	8.26	143	48	25.13	HARVARD UNIVERSITY (USA)	171 (7.40%)
3	CHINA	6.71	142	13	8.39	UNIVERSITY COLLEGE LONDON (UK)	167 (7.23%)
4	CANADA	5.54	107	21	16.41	HARVARD MEDICAL SCHOOL (USA)	128 (5.54%)
5	GERMANY	5.28	97	25	20.49	YALE UNIVERSITY (USA)	123 (5.32%)
6	ITALY	5.28	109	13	10.66	HARVARD UNIVERSITY MEDICAL AFFILIATES (USA)	118 (5.11%)
7	AUSTRALIA	2.55	50	9	15.25	UNIVERSITY OF FLORIDA (USA)	114 (4.93%)
8	SWEDEN	2.08	33	15	31.25	STATE UNIVERSITY SYSTEM OF FLORIDA (USA)	98 (4.24%)
9	FRANCE	1.95	38	7	15.56	UNIVERSITY OF CALGARY (Canada)	95 (4.11%)
10	NETHERLANDS	1.90	38	6	13.64	UNIVERSITY OF TORONTO (Canada)	95 (4.11%)

Abbreviations: SCP, Single Country Publications; MCP, Multiple Country Publications; MCP Ratio, MCP / (SCP + MCP).

Figure 4.

Scientific collaboration network map of major global publishing countries and regions.

The United States produced 670 single-country publications and 58 multiple-country publications, with an international collaboration rate of 7.97%. This suggests that although the United States was the largest contributor in this field, its research output was still mainly based on domestic teams. In contrast, the international collaboration rates were 25.13% for the United Kingdom, 31.25% for Sweden, and 20.49% for Germany. Although these countries had lower total publication output than the United States, they were more active in international collaboration. China had an international collaboration rate of 8.39%, similar to that of the United States, indicating that its related research still relies more on domestic teams and that there remains room to strengthen the depth of international collaboration.

The country/region collaboration network in Figure 4 further shows that the United States occupies a central position in the collaboration network, with the largest node and clear links with the United Kingdom, Canada, Germany, Italy, China, Australia, and other countries. This indicates that the United States not only leads in publication output but also serves as a key hub in the international collaboration network. Overall, international collaboration in this field is mainly concentrated in North America, Europe, and parts of Asia, suggesting that further strengthening cross-regional collaboration remains important.

At the institutional level, Table 1 shows that the University of London had the highest occurrence frequency, with 189 occurrences, accounting for 8.18%. It was followed by Harvard University, University College London, Harvard Medical School, Yale University, and Harvard University Medical Affiliates. These institutions are mainly located in the United Kingdom and the United States, which is broadly consistent with the country-level research pattern. In addition, the University of Florida, University of Calgary, and University of Toronto were also among the top 10, indicating that North America has a strong institutional foundation in this field.

Figure 5 presents the collaboration network of major institutions worldwide. University College London appears as a relatively large core node in the network, indicating that it was not only active in publication output but also had strong collaborative connections. Harvard University, Yale University, Hannover Medical School, the University of Calgary, and the University of Florida also occupied important positions in the network. Overall, institutional collaboration in this field showed a multicenter pattern, characterized by the leading role of high-level research institutions in the United Kingdom and the United States, together with active participation from research teams in Europe and Canada.

Figure 5.

Scientific collaboration network map of major global institutions.

Core Authors and Author Collaboration Network

Table 2 lists the top 10 authors by publication output in this field, and Figure 6 presents the global collaboration network of core authors. Murphy T had the highest publication output, with 58 articles and a TLS of 96, indicating that this author ranked first not only in productivity but also showed strong connectivity within the author collaboration network. Cavanna A published 51 articles with a TLS of 44; Müller-Vahl K published 46 articles with a TLS of 46; Robertson M published 44 articles with a TLS of 30; Leckman J published 37 articles with a TLS of 32; and Storch E published 37 articles with a TLS of 87. These results suggest that the core authors in this field include both highly productive researchers and those with strong organizational roles in the collaboration network.

Table 2.

Top 10 Authors in Research

Rank	Author	Articles	Institution	Country	Citation	TLS
1	MURPHY T	58	University of South Florida	USA	2248	96
2	CAVANNA A	51	University of Birmingham	UK	2576	44
3	MÜLLER-VAHL K	46	Hannover Medical School	Germany	1075	46
4	ROBERTSON M	44	University College London	UK	3049	30
5	LECKMAN J	37	Yale School of Medicine	USA	4060	32
6	STORCH E	37	Baylor College of Medicine	USA	2131	87
7	MARTINO D	34	University of Calgary	Canada	806	46
8	PIACENTINI J	33	University of California, Los Angeles	USA	1627	58
8	MATAIX-COLS D	28	Karolinska Institutet	Sweden	1479	35
10	OKUN M	27	University of Florida	USA	656	2

Abbreviation: TLS, Total Link Strength.

Figure 6.

Scientific collaboration network map of global core authors.

In terms of citation frequency, Leckman J had the highest total citations, with 4060 citations, followed by Robertson M with 3049, Cavanna A with 2576, Murphy T with 2248, and Storch E with 2131. The high citation counts of Leckman J and Robertson M suggest that their studies have had a substantial foundational influence on the understanding of the clinical phenotype, developmental trajectory, and psychiatric comorbidities of Tourette syndrome. Murphy T and Storch E, meanwhile, showed both high publication output and high TLS, indicating that their teams have been particularly active in sustained collaboration, clinical research, and comorbidity assessment.

Figure 6 shows that the author collaboration network formed several relatively distinct research groups. The group centered on Murphy T and Storch E showed close internal connections and may mainly focus on topics such as Tourette syndrome in children and adolescents, anxiety and depression, OCD, ADHD, and behavioral interventions. Cavanna A and collaborators formed another important group, reflecting more strongly the characteristics of European neuropsychiatric and clinical phenotype research. The group involving Müller-Vahl K appeared to be more closely associated with adult Tourette syndrome, pharmacological treatment, tic disorders, and functional tic-like behaviors. These findings indicate that this field is not dominated by a single academic team, but is jointly advanced by multiple research groups spanning psychiatry, neurology, child and adolescent medicine, and psychology.

Journal and Co-Cited Journal Analysis

Table 3 lists the top 10 journals by publication output and the top co-cited journals in this field. In terms of publishing journals, Frontiers in Psychiatry had the highest number of publications, with 51 articles, followed by Journal of Child and Adolescent Psychopharmacology, Movement Disorders, Journal of the American Academy of Child and Adolescent Psychiatry, and Psychiatry Research. These journals are mainly distributed across psychiatry, child and adolescent psychiatry, movement disorders, and neuropsychopharmacology, indicating that research on depression and Tourette syndrome has a clear neuropsychiatric interdisciplinary nature.

Table 3.

Top 10 Journals and Co-Cited Journals in Research

Rank	Journals	Articles	2025 IF	JCR Quartile	Co-Cited Journals	Citations
1	Frontiers in Psychiatry	51	3.2	Q2	Journal of the American Academy of Child & Adolescent Psychiatry	2877
2	Journal of Child and Adolescent Psychopharmacology	41	2.2	Q2	Neurology	2717
3	Movement Disorders	38	7.6	Q1	American Journal of Psychiatry	2178
4	Journal of the American Academy of Child and Adolescent Psychiatry	29	9.5	Q1	Movement Disorders	1875
5	Psychiatry Research	28	3.9	Q1	Archives of General Psychiatry	1483
6	European Child & Adolescent Psychiatry	27	4.9	Q1	Biological Psychiatry	1398
7	Brain Sciences	23	2.8	Q3	Journal of Clinical Psychiatry	1201
8	Movement Disorders Clinical Practice	22	2.7	Q2	Brain	1196
9	Neuroscience and Biobehavioral Reviews	21	7.9	Q1	Lancet	979
10	European Child and Adolescent Psychiatry	20	4.9	Q1	Journal of Child and Adolescent Psychopharmacology	947

Notably, Movement Disorders, Journal of the American Academy of Child and Adolescent Psychiatry, Psychiatry Research, European Child & Adolescent Psychiatry, and Neuroscience and Biobehavioral Reviews are all JCR Q1 journals, suggesting that this research topic has received attention from high-impact journals. Meanwhile, Q2 journals such as Frontiers in Psychiatry and Journal of Child and Adolescent Psychopharmacology have also provided important publication platforms for this field.

In terms of co-cited journals, Journal of the American Academy of Child & Adolescent Psychiatry had the highest citation frequency, with 2877 citations, followed by Neurology, American Journal of Psychiatry, Movement Disorders, and Archives of General Psychiatry. These co-cited journals constitute an important knowledge base for this field. Among them, the frequent appearance of journals in child and adolescent psychiatry suggests that developmental stage is an important dimension in research on depression and Tourette syndrome. Meanwhile, the high citation frequency of journals such as Neurology and Movement Disorders indicates that tic symptoms and neurobiological mechanisms remain fundamental components of this field.

Reference Burst Analysis

Figure 7 presents the top 20 references with the strongest citation bursts in this field. Reference burst analysis can identify key publications that received rapid scholarly attention during a specific period, thereby reflecting stage-specific changes in research themes and academic focus.

Figure 7.

Top 20 references with the strongest citation bursts in research.

As shown in Figure 7, burst references were distributed across different time periods, indicating that the knowledge base of this field has undergone continuous evolution. Early burst references were mainly related to clinical diagnosis, pharmacological treatment, and tic symptom management, reflecting an initial focus on the basic clinical features and symptom control of Tourette syndrome. In the middle stage, burst references began to involve more psychiatric comorbidities, including obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, anxiety, and depression. This suggests that researchers gradually recognized Tourette syndrome not merely as a tic disorder, but as a complex neuropsychiatric condition accompanied by multiple psychological and psychiatric problems.

In recent years, burst references have focused more on systematic reviews, clinical guidelines, mental health outcomes, and assessment scales. This shift indicates that the field is moving from single-symptom research toward comprehensive assessment and evidence-based integration. The research focus is no longer limited to tic control, but has further expanded to long-term functioning, quality of life, emotional burden, and the need for individualized treatment.

High-Frequency Keywords and Keyword Co-Occurrence Network

Table 4 lists the top 20 keywords with the highest occurrence frequencies in this field, and Figure 8 presents the co-occurrence network of core keywords. The results showed that “Tourette syndrome” had the highest occurrence frequency, appearing 589 times with a TLS of 938, making it the central node of the entire keyword network. It was followed by “Tics/tic disorders”, “Obsessive-compulsive disorder”, “Neuromodulation/deep brain stimulation”, “Attention-deficit/hyperactivity disorder”, “Children”, “Depression”, and “Comorbidity.”

Table 4.

Top20 Keywords in Research

Rank	Keyword	Occurrences	TLS	Rank	Keyword	Occurrences	TLS
1	Tourette syndrome	589	938	11	Anxiety disorders	86	204
2	Tics/tic disorders	399	677	12	Psychiatric disorders	71	80
3	Obsessive-compulsive disorder	276	485	13	Schizophrenia	59	111
4	Neuromodulation/deep brain stimulation	215	341	14	Treatment	54	94
5	Attention-deficit/hyperactivity disorder	190	372	15	Mental health	50	69
6	Children	157	308	16	Quality of life	47	108
7	Depression	155	366	17	Dopamine	42	69
8	Comorbidity	151	253	18	Antipsychotics	38	47
9	Autism spectrum disorder	116	174	19	Parkinson’s disease	37	83
10	Adolescents	96	199	20	Psychiatry	35	44

Notes: To ensure data consistency, synonymous keywords were manually merged before ranking. For instance, “Tourette’s syndrome”, “Gilles de la Tourette syndrome”, “Tourette disorder”, and “TS” were combined as “Tourette syndrome”; “tic”, “tics”, “motor tics”, “vocal tics”, and “phonic tics” were combined as “Tics”; “tic disorder”, “chronic tic disorder”, and “persistent tic disorder” were combined as “Tic disorders”; “depressive symptoms”, “depressive disorder”, and “depression” were combined as “Depression”; “MDD”, “major depression”, and “major depressive disorder” were combined as “Major depressive disorder”; and “ADHD” and “attention deficit hyperactivity disorder” were combined as “Attention-deficit/hyperactivity disorder”.

Abbreviation: TLS, Total Link Strength.

Figure 8.

Scientific collaboration network map of global core keywords.

These keywords and their TLS values indicate that this field is not centered solely on tic symptoms. Instead, it has formed a knowledge network with Tourette syndrome as the core, extending toward psychiatric comorbidities and therapeutic interventions. Among these terms, “Depression” showed both a relatively high occurrence frequency and TLS, suggesting that depression has become an important connecting node in Tourette syndrome research rather than a peripheral topic. Together with keywords such as “Comorbidity”, “Anxiety disorders”, “Mental health”, and “Quality of life”, it forms a thematic cluster related to psychiatric and psychological burden. From the perspective of the disease spectrum, the high frequency of “Obsessive-compulsive disorder” and “Attention-deficit/hyperactivity disorder” is consistent with the common comorbidity profile of Tourette syndrome. OCD and ADHD have long been regarded as major psychiatric comorbidities of Tourette syndrome, while depression may be associated with long-term symptom burden, social stigma, academic or occupational impairment, family stress, and shared neurobiological mechanisms. Notably, in Table 4, “Dopamine” appeared 42 times with a TLS of 69, and “Antipsychotics” appeared 38 times with a TLS of 47. This suggests that although dopaminergic mechanisms and antipsychotic medications were not among the most frequent topics, they still constitute an important foundation for treatment and neurobiochemical mechanisms.

Figure 8 shows links between “Tourette syndrome” and the keywords “tics”, “obsessive-compulsive disorder”, “attention-deficit/hyperactivity disorder”, “depression”, and “comorbidity.” Depression was thus connected to several psychiatric comorbidity topics in the analyzed literature. These links indicate which topics were studied together, without measuring the direction or strength of clinical relationships between disorders.

Thematic Evolution, Keyword Clustering, and Keyword Burst Analysis

Figure 9 presents the thematic evolution river map of this field. Overall, the research themes have shifted from pharmacological treatment and tic control, to psychiatric comorbidities and psychological outcomes, and further toward evidence-based integration and comprehensive mental health assessment. Early studies focused more on clinical trials, pharmacological treatment, serotonin reuptake inhibitors, fluoxetine, clonidine, placebo, side effects, and drug withdrawal. This indicates that the main task during this stage was to identify pharmacological strategies capable of controlling tics and accompanying psychiatric symptoms.

Figure 9.

Theme Evolution River Map in Research.

The keyword clustering and timeline map in Figure 10 further shows that this field has formed several thematic clusters, including “tic disorder”, “psychiatric disorder”, “movement disorder”, “antipsychotic drugs”, “depression”, “causal relationship”, “comorbidity”, “potential mechanisms”, and “therapeutic strategies.” These clusters indicate that Tourette syndrome research has expanded beyond the traditional framework of movement disorders to multiple dimensions, including neurodevelopment, psychiatric comorbidities, pharmacological mechanisms, psychosocial functioning, and treatment strategies.

Figure 10.

Keywords clustering visualization and timeline evolution map.

Figure 11 shows that early burst keywords mainly included “clinical trial”, “serotonin uptake inhibitor”, “side effect”, “fluoxetine”, “weight gain”, “clonidine”, “placebo”, and “drug withdrawal.” These keywords are strongly associated with pharmacological treatment, indicating that early research focused mainly on drug efficacy, safety, and tolerability, particularly the roles of serotonergic drugs, α2-adrenergic receptor agonists, and antipsychotic medications in managing tics and comorbid symptoms.

Figure 11.

Top15 keywords with the highest burst strength in research.

In recent years, burst keywords have clearly shifted toward “psychology”, “systematic review”, “mental health”, “tics”, “Yale global tic severity scale”, and “attention deficit hyperactivity disorder.” Among them, the bursts of “systematic review”, “mental health”, “Yale global tic severity scale”, and “attention deficit hyperactivity disorder” continued until 2025, suggesting that the current research frontier has moved from single-treatment studies toward evidence-based synthesis, standardized assessment, and overall mental health outcomes. In particular, the sustained burst of “mental health” reflects a shift in Tourette syndrome research from “how to reduce tics” to “how to improve patients’ overall psychological functioning and quality of life.”

Discussion

Based on data from the WOSCC and Scopus, this study conducted a systematic bibliometric analysis of publications related to depression and Tourette Syndrome from 2001 to 2025. The findings show increasing attention to psychiatric comorbidities, mental health, and functional outcomes alongside research on tic symptoms and treatment. The discussion below relates these patterns to published clinical findings and the questions they leave unresolved.

General Information Overview

Publication and Citation Trends

Annual publication output increased overall, indicating sustained research interest in depression and TS. This growth accompanied broader attention to psychiatric comorbidities, functional impairment, and quality of life. Publication volume alone, however, does not show whether the evidence for a particular clinical relationship has become stronger.

Publications from earlier periods have had more time to accumulate citations. Lower citation frequencies in recent years may therefore reflect citation lag rather than reduced research value. Citation counts are best considered alongside keyword bursts and thematic evolution when interpreting recent research activity.

Core Countries and Institutional Collaboration Patterns

The United States led publication output, although its proportion of multiple-country publications was relatively limited. The United Kingdom, Germany, and Sweden showed higher international collaboration rates, suggesting different patterns of research collaboration across countries.

The University of London, Harvard University, University College London, Harvard Medical School, and Yale University were prominent contributors. Their collaboration networks identify potential partners for studies of TS and depression. Multicenter work could support consistent assessment across settings, although institutional affiliations do not establish where study participants were recruited.

Core Author Groups and Their Collaboration Network

The author network contained several groups with sustained publication and collaboration activity. Murphy T and Storch E combined high publication output with strong links, while Leckman J and Robertson M had high citation counts. These patterns describe contributions to the literature but do not establish the clinical relevance of every publication.

Collaboration between these groups could help compare depression assessments and comorbidity profiles across studies. Such comparisons require examination of the original research, beyond the authors’ positions in the network.

Publishing Journals and Co-Cited Influence

The journal distribution reflects contributions from psychiatry, child and adolescent mental health, and movement disorders. Prominent venues included Frontiers in Psychiatry, Journal of Child and Adolescent Psychopharmacology, and Movement Disorders. Journal of the American Academy of Child and Adolescent Psychiatry and Psychiatry Research also contributed to this literature.

The co-cited journals similarly connect psychiatric and neurological research on TS. This overlap is relevant to depression because its assessment involves emotional symptoms and functioning alongside tic severity. Journal and citation patterns identify sources of research, while individual studies determine what those sources contribute to clinical understanding.

Key References and the Developmental Trajectory of the Field

Reference bursts indicate a broadening of attention from diagnosis, tic control, and pharmacological treatment toward psychiatric comorbidity and mental health outcomes. More recent themes include systematic reviews, clinical guidelines, and standardized assessment. These developments help locate the research questions around which evidence has accumulated.

A citation burst identifies increased attention to a reference, rather than a judgment about its methodological quality. The clinical studies discussed below provide context for these themes; they are not presented as a complete appraisal of all burst references.

Core Keywords and Thematic Evolution

The keyword network links depression with OCD, ADHD, anxiety, and other comorbidity topics. “Tourette syndrome” and “Tics/tic disorders” remained central terms, alongside clusters concerning mental health and quality of life. Depression occurred less frequently than OCD and ADHD but showed relatively strong links within the network. This pattern places depression within a broader body of psychiatric comorbidity research.

The thematic analysis suggests increasing attention to standardized assessment and outcomes beyond tic control. The sustained burst of the Yale Global Tic Severity Scale indicates continued interest in tic measurement. Whether studies also capture depressive symptoms and everyday functioning requires examination of their clinical outcomes.

Research Hotspots and Trend Evolution

Keyword co-occurrence, burst patterns, and thematic evolution identify several connected research trends. Clinical findings help explain what these trends mean for understanding depression in TS.

Research on psychiatric comorbidity increasingly considers depression alongside anxiety, OCD, and ADHD. Clinical studies differ in their findings on depression and other psychiatric comorbidities. In a cross-sectional study, Hirschtritt et al examined psychiatric diagnoses in 1374 individuals with TS. They reported frequent comorbidity and an association between mood disorders and OCD. Their outcome category included mood disorders rather than depression alone.¹¹ Rizzo et al associated depression in a pediatric sample with tic severity, ADHD, anxiety, and behavioral problems. Obsessive-compulsive symptom severity did not distinguish depressed from non-depressed patients in that sample.¹² Differences in populations and outcome definitions limit direct comparison, but both studies show why depression should be examined within the wider comorbidity profile.

Pharmacological research has addressed drug efficacy, safety, and tolerability, as reflected in keywords such as “clinical trial”, “fluoxetine”, “clonidine”, “side effect”, and “drug withdrawal.” Interpreting this work for patients with depression requires attention to the symptoms being assessed. Piedad and Cavanna compared 65 adults with TS, 696 participants with recurrent major depressive disorder, and 293 healthy controls. The TS group reported higher depressive symptom scores than healthy controls and more frequent irritability than the recurrent depression group.¹³ Different Beck Depression Inventory versions were used, with 14 items available for direct comparison. These findings concern symptom presentation rather than comparative treatment efficacy, but they help identify outcomes that treatment studies should assess.

Standardized assessment and functional outcomes form another area of growing interest. Watson et al examined quality of life in 38 adolescents with TS and 28 controls. Within the TS group, higher combined anxiety-depression scores were associated with poorer quality of life, whereas tic severity was not.¹⁴ Quality of life did not differ significantly between the recruited groups, although the TS group scored below population norms. Family functioning remained associated with quality of life in adjusted analyses. The combined symptom measure does not isolate depression, and the small, cross-sectional sample limits causal interpretation. Nevertheless, the findings explain why depressive symptoms and psychosocial functioning deserve attention alongside tic scores.

Neuromodulation remains a prominent topic, particularly research on deep brain stimulation (DBS). Its presence in the keyword network does not establish an antidepressant effect in TS. Studies addressing TS with co-occurring depression should report emotional and functional outcomes alongside changes in tics. This would help distinguish improvements in motor symptoms from changes in patients’ mental health and daily lives.

Longitudinal research addresses the temporal relationship between TS and later depression. Chou et al examined a claims-based cohort of 1337 patients with TS and a matched comparison cohort in Taiwan. The adjusted hazard ratio for subsequently diagnosed depression was 4.85 (95% confidence interval, 3.46–6.79).³⁸ This finding supports a temporal association without resolving the underlying causal mechanism. It also measures a different outcome from prevalence or cross-sectional symptom scores. Further follow-up could examine how depressive symptoms develop alongside changes in tics, other psychiatric conditions, treatment exposure, and psychosocial circumstances.

These studies address psychiatric diagnoses, subsequent depression risk, symptom profiles, and quality of life. Their findings connect the bibliometric themes to clinical questions, while showing the importance of age, comorbidity, and measurement when comparing results.

The clinical studies discussed here support assessing depression separately from tic severity. The 2019 American Academy of Neurology guideline recommends screening people with tics for mood, anxiety, and disruptive behavior disorders. It also recommends assessing suicidal thoughts and attempts in people with TS.³³ When depression is identified, timely clinical evaluation and appropriate evidence-based treatment should form part of the management plan, with referral to mental health services when needed. Addressing depressive symptoms alongside tics can make care more responsive to patients’ mental health and functional needs. These recommendations provide an established basis for clinical assessment rather than a new recommendation derived from bibliometric analysis. Reporting tic severity, depressive symptoms, other psychiatric symptoms, and functional outcomes separately would help evaluate whether management improves more than tics. Medication and neuromodulation choices require evidence specific to the intervention and assessment of the individual patient’s needs.

Limitations and Future Research Recommendations

This study has several limitations relating to coverage, data processing, and interpretation. WOSCC and Scopus may omit relevant publications indexed elsewhere, including work in regional journals. Restricting the analysis to English-language articles and reviews may also underrepresent findings published in other languages. Variations in keywords, author names, and institutional affiliations can affect results despite harmonization. Citation frequency and burst strength depend partly on publication age, so recent work has had less opportunity to accumulate citations.

Bibliometric indicators describe scholarly activity and attention rather than methodological quality or clinical effectiveness. They cannot establish causality or determine whether a treatment improves depression in TS. The narrative comparison provides clinical context but covers selected studies without a formal risk-of-bias assessment of the entire dataset. The research priorities identified here should be understood within this scope.

Further longitudinal research should distinguish temporal associations from causal explanations of depression in TS. Repeated assessments could clarify the contribution of tic severity, co-occurring disorders, treatment exposure, and psychosocial factors to changes in depressive symptoms. Existing cohort findings provide a basis for this work, but repeated clinical assessments could clarify how these relationships develop.¹⁸

Cross-national and multicenter studies could examine whether findings are consistent across populations and healthcare settings. Shared definitions and assessment schedules would improve comparisons, particularly when distinguishing depressive disorders from symptom elevations or combined anxiety-depression measures. Where feasible, studies should report both diagnostic status and symptom severity.

Future intervention studies should assess depression and functional outcomes alongside tics, document concurrent treatment for psychiatric comorbidities, and follow outcomes beyond the immediate treatment period. Reporting these outcomes would help compare the benefits of interventions across studies and patient groups. A multidimensional approach would help determine which aspects of patients’ mental health and daily functioning improve with treatment.

Conclusion

This analysis of 2311 publications maps the development of research on TS and depression from 2001 to 2025. Research activity increased, and its themes expanded beyond tic control to psychiatric comorbidity, mental health, and functional outcomes. Comparison with clinical studies supports distinguishing depressive symptoms from other comorbidities and assessing outcomes beyond tic severity. Future research should clarify longitudinal relationships, improve the comparability of depression measures, and evaluate depressive and functional outcomes alongside tics. These priorities can guide further investigation of depression in TS and its clinical consequences.

Funding Statement

1. Postdoctoral Research Fund Project of Heilongjiang Province (LBH-Z20081); 2. Scientific Research Project of Heilongjiang Provincial Administration of Traditional Chinese Medicine (ZHY 2022-191); 3. Special Fund for Talents of the Fourth Affiliated Hospital of Heilongjiang University of Traditional Chinese Medicine: FSRC2024MS02.

Disclosure

The authors report no conflicts of interest in this work. Jin Dai and Mingyuan Xu are the first authors.