The Web of Science (WOS) database was used for the literature retrieval. The final search strategy was: TS=(“psoriasis” OR “psoriatic disease”) AND TS=(“microbiota” OR “microbiome” OR “flora” OR “microbial community”). Literature published from the establishment of the database (2003) to October 15, 2024, was considered. The document types were limited to articles and review articles, and the publication language was restricted to English. A total of 588 articles met the inclusion criteria, including 335 research articles and 254 review articles. The selected publications were exported in a plain text file format, following the “full record and cited references” format. To ensure data reliability, two authors independently conducted the retrieval using the same search strategy, and any discrepancies were cross-checked.

Citation analysis and visualization of authors, journals, years, countries, keywords, research objectives, and publications were conducted using CiteSpace (version 6.3.R1), R4.2.2 Biblometrics package, Scimago Graphica 1.0.45 and VOSviewer (version 1.6.20.0). The overall workflow of the analysis is shown below ( Figure 1 ).

The number of publications and citation frequency are essential indicators of the development trajectory and potential growth of a research field. Between 2004 and 2014, the research output remained relatively stable, with the annual number of publications generally staying below 10. The second phase, from 2014 to 2024, marked a period of growth, with a noticeable increase in publications, particularly in 2021 when the number of publications peaked. From 2021 to 2024, the publication volume exhibited a fluctuating trend, but our study only includes data up to October 2024, meaning that publication volume and citation frequency for 2024 may continue to rise. The rise in publications can be attributed to the rapid adoption of high-throughput sequencing technologies for analyzing gut microbiota, which has made it possible to analyze unculturable bacteria, thus significantly enriching the gut microbiome database and linking microbial characteristics to specific physiological states or diseases (Quince et al., 2017). The field’s average Annual Growth Rate (AGR) is 17.91%, indicating strong potential for further research on psoriasis and the gut microbiota.

This study includes 1158 institutions across 68 countries and regions, with 3471 authors contributing. Supplementary Table 1 provides a breakdown of the top ten countries in terms of academic output. The United States leads in total citation frequency (5662) and average citations per article (59), surpassing most other countries globally. Among the top ten countries, two institutions from the United States—specifically the University of California System—emerged as the most productive research institutions, publishing 58 articles, reflecting the country’s strong scientific leadership in psoriasis and gut microbiota research. Notably, while China ranks lower than the United States and Italy in citation frequency, it has the highest number of publications, accounting for 21.1% of the total number of articles.

In Figure 2A , the top 10 countries/regions are categorised based on the number of articles authored by a single corresponding author (in red) and multiple corresponding authors (in blue). Figure 2B shows the publication trends of the top five countries, illustrating how the number of publications on psoriasis and gut microbiota has changed over time. It highlights that China began to experience a rapid increase in publication volume starting in 2020 and has now become the leading country in terms of publication output, underscoring China’s current dominant position in psoriasis and gut microbiota genomics research.

Figure 2C illustrates the institutional collaboration network, where nodes with similar colors represent a common cluster, highlighting close collaborative relationships. The strength of the connecting lines between nodes indicates the intensity of cooperation between institutions. Karolinska Institutet stands out in the field and has the highest level of collaboration strength. It is the most closely connected university, having established collaborative relationships with 23 institutions. The results also show frequent exchanges between Karolinska Institutet and the University of Pécs, as well as with King’s College London.

Figure 2D depicts a map of publications by country/region. Nodes in different colors represent different countries/regions, with the size of each node reflecting the number of articles contributed by that particular country/region. The strength of the connections between nodes indicates the intensity of cooperation between countries.

Supplementary Table 2 lists the top 10 authors in psoriasis and gut microbiota research based on their h-index. Supplementary Figure 1 shows the top 10 authors by publication volume. A higher h-index indicates greater influence in the research field. Notably, four of the top authors are from Poland. Supplementary Figure 2 identifies the authors with the highest total citation counts in the field. RUDNICKA LIDIA from the Medical University of Warsaw is not only the most productive author in this field, but also holds the highest h-index, g-index, and m-index. The authors with the highest total citation counts are RENDON ADRIANA (USA) and SCHAEKEL KNUT (Germany). Although their h-indexes are lower due to fewer publications, they are still core authors in the field of psoriasis and gut microbiota research. Supplementary Figure 3 highlights BLASER, MARTIN J (USA, Rutgers University) as the most cited author in psoriasis and gut microbiota research. His papers have been cited the most by other studies in this field, indicating that his work has received widespread attention and recognition in this specific area of research.

Figure 3A depicts a co-authorship network, illustrating the collaboration among authors in this field. Figure 3B adds a temporal dimension to this network, showing how author collaboration has evolved over time.

Figure 4 displays the connections between authors (left), keywords (center), and author nationality (right), with the width of the branches representing the volume of publications. This visualisation provides a comprehensive overview of the global research landscape and emphasises the central role of specific keywords and regions in shaping the field.

Through a detailed statistical analysis of academic publications, co-citations, and author collaboration, we gain a more accurate understanding of the knowledge landscape in psoriasis and gut microbiota. This analysis contributes to identifying the factors that have facilitated success in high-impact regions and institutions, providing valuable insights for further research.

Analyzing journal co-citations allows us to identify journals with significant influence in a specific research field. These studies were published in 254 different journals. The top 10 journals were selected based on the number of citations. The journals were ranked by total citations, H-index, and impact factor (2023). The most frequently cited journal is the International Journal of Molecular Sciences, which published 28 articles, accounting for 4.76% of the total, with a total of 1,664 citations. This journal also holds the highest H-index, G-index, and M-index. More than half of the top journals are Swiss journals. Frontiers in Microbiology ranks second in M-index.

Supplementary Figure 4 presents the top ten most cited journals. Journal of Investigative Dermatology (J Invest Dermatol), British Journal of Dermatology (Brit J Dermatol), and Journal of Allergy and Clinical Immunology (J Allergy Clin Immunol) have each been cited more than 1,000 times, with J Invest Dermatol leading the list with a total of 1,643 citations. All of the top 10 journals have an impact factor (IF) greater than 3.5, with the British Journal of Dermatology having the highest IF (11). This journal was the first to publish research on psoriasis and gut microbiota and is one of the leading journals in dermatology, underscoring the significance and high quality of research in the field of psoriasis and gut microbiota. Supplementary Figure 5 illustrates the journal co-occurrence network over time. It shows that in recent years, the most frequently published journals in the field are the International Journal of Molecular Sciences and Frontiers in Microbiology.

Table 1 summarises the ten most locally cited references. The article “ Decreased bacterial diversity characterises the altered gut microbiota in patients with psoriatic arthritis, resembling dysbiosis in inflammatory bowel disease” by SCHER JU and colleagues, published in Arthritis & Rheumatology in 2015, is the most cited reference in the field, with 124 citations. The study explored the role of gut microbiota in psoriatic arthritis, finding that patients with psoriatic arthritis exhibit reduced gut microbiota diversity, similar to the dysbiosis observed in inflammatory bowel disease. These findings support the potential link between gut microbiota and systemic inflammation.

The ten most cited papers globally are listed in Table 2 . The article by RENDON A. and colleagues, published in 2019 in the International Journal of Molecular Sciences, is the most cited, with 1,048 citations. This paper discusses the close relationship between gut microbiota and inflammatory diseases in psoriasis patients. The study demonstrates that dysbiosis may exacerbate the inflammatory response in psoriasis by influencing the regulatory functions of the immune system. Changes in gut microbiota can directly affect the immune response, thereby intensifying systemic inflammation, particularly in diseases like psoriasis that have multi-system involvement. The article also explores the potential of modulating gut microbiota as a therapeutic target to improve clinical symptoms in psoriasis patients.

Figure 5A illustrates the co-citation network of the literature, while Figure 5B presents the top 100 articles based on citation frequency. Figure 5C provides a visual network of co-cited references clustered by thematic direction, including terms such as skin microbiome, plaque psoriasis, gut microbiota, short-chain fatty acids, T-cell subsets, bidirectional Mendelian randomization, and skin-gut axis. Figure 5D displays a timeline of co-cited reference clusters from the past decade, allowing for an in-depth understanding of the evolution of the psoriasis-gut microbiota knowledge base. The initial cluster, labeled #0 Skin Microbiome, represents the embryonic stage of psoriasis microbiome research. This marks the beginning of targeted broad studies in the field, notably published by Elizabeth A. Grice in Science. Her study revealed significant diversity in skin microbiota across different body sites, with distinct differences between moist, dry, and sebaceous-rich areas. The skin microbiome shows both stability and variability in healthy versus disease states (e.g., psoriasis). Clusters #1 and #2 illustrate the current state of research in key areas. In cluster #3, an article by Xue Zhou (2024) in Microbiology Spectrum concisely discusses the role of Eubacterium rectale as a key gut microbiota marker in psoriasis patients. Reducing butyrate-producing bacteria, such as Eubacterium rectale, may promote systemic inflammation in psoriasis patients. Cluster #4 features the latest contributions from Jose U. Scher and colleagues, emphasizing the role of gut microbiota in inflammatory arthritis, particularly how specific gut microorganisms (e.g., Lactobacillus bifidus and Prevotella) influence immune responses and impact the development of inflammation and damage in psoriatic arthritis. Cluster #5 highlights recent studies focusing on how genetic variations affect gut microbiota diversity and composition, revealing gene-environment interactions in metabolic, nutritional, and immune health. Cluster #6 examines the relationship between biologics and gut microbiota in psoriasis.

Through the organization of key literature, Figure 6 provides an overview of observational and interventional studies on the gut microbiota in patients with psoriasis and/or psoriatic arthritis, compared to healthy controls. The studies found that, compared to the healthy group, psoriasis patients exhibited a significant increase in gut microbiome diversity, with notable differences in the composition of phyla such as Bacteroides and Firmicutes (Codoñer et al., 2018; Todberg et al., 2021). Some studies have shown that regardless of genetic background, changes in the order Clostridiales and Streptococcaceae contribute to the exacerbation of disease progression in a mouse model of psoriasis induced by imiquimod (Zákostelská et al., 2016). These findings also support using symbiotic microorganisms as possible probiotic formulations.

After excluding redundant or irrelevant keywords, Figure 7A presents a temporal analysis of keyword trends. In Figure 7B , the top 20 keywords are displayed over time, with red dots indicating periods of high research activity, reflecting specific temporal hotspots in the field. This study identifies 20 influential terms related to the psoriasis drug delivery system, including Crohn’s disease, association, psoriatic arthritis, rheumatoid arthritis, inflammatory bowel disease, ankylosing spondylitis, regulatory T cells, Th17 cells, ulcerative colitis, microbiome, bacteria, identification, mice, innate lymphoid cells, severity, skin inflammation, prevalence, health, NF-kappa B, and plaque psoriasis. Figure 7C illustrates the keyword co-occurrence network in the research domain. In contrast, Figure 7C visualizes clusters of research within the field of psoriasis gut microbiome into five distinct areas: Cluster #0 Local Transdermal Drug Delivery, Cluster #1 Atopic Dermatitis, Cluster #2 Dendritic Cells, Cluster #3 Pathogenesis, Cluster #4 Diversity, and Cluster #5 Double-Blind Studies. To enhance clarity, Figure 7E integrates a timeline analysis on top of the clusters, offering a clearer view of how trends evolve. This approach also allows a better understanding of inter-cluster relationships through node linkages. The timeline analysis indicates that the current research frontiers include Cluster #0 Precision Medicine, Cluster #1 Stratum Corneum, Cluster #2 Gut-Skin Axis, Cluster #3 Barrier Function, and Cluster #4 Antimicrobial Peptides in Inflammatory Bowel Disease.

Based on the number of indexed publications, we identified two distinct phases in the growth of psoriasis and gut microbiota research. From 2004 to 2014, the annual number of publications was in the single digits, when high-throughput sequencing had not yet gained widespread adoption. During this time, most researchers relied on traditional culture-based methods. However, traditional microbial culturing techniques are inherently limited by the unavoidable enrichment or depletion of specific strains, which alters the original microbial ecosystem and can lead to significant bias in research findings.

The development of research literature is also closely linked to the strategic initiatives undertaken by various countries in gut microbiota research. Worldwide, numerous countries have launched national programs aimed at advancing microbiome research. For instance, the European Union led the “MetaHIT” (Human Microbiome Project) initiative in 2008, while the United States launched the “Human Microbiome Project” (HMP) in 2007. In 2017, China initiated its national program, the “Chinese Gut Metagenomics Project.” (Wang et al., 2020).

With these programs’ initiation, the research volume saw a significant increase after 2014. With the advent of high-throughput sequencing and big data technologies, scientists could perform bulk and single-cell sequencing of the gut microbiota, enabling rapid analysis of the microbial composition in the gut and its correlation with the health status of the subjects. The development of new technologies, the introduction and popularization of metabolomics, and the concept of the microbiome-skin axis have propelled the research on gut microbiota into a period of rapid growth. As government and international agency-supported initiatives were implemented, the number of studies reached its peak in 2021.

The number of publications from 2021 to 2024 has remained stable, indicating that research on the gut microbiota in psoriasis has entered a relatively mature phase. During this period, the changes in the gut microbiota in psoriasis have been thoroughly explored, with no significant technological breakthroughs. The pace of new research findings has stabilized. A significant reason for this stability is the lack of substantial changes in funding for this field.

Recently, a group of Chinese scientists, collaborating with researchers from 14 other countries including the United States, published a joint editorial in Cell Research, advocating for the initiation of Phase II of the Human Genome Project (HGP2). This article reflects the academic community’s recognition of gut microbiota research’s growing importance and direction. The study of gut microbiota in psoriasis is emerging as a hot research topic for the future. Since our statistics only cover up to October 2024, the number of publications in 2024 may further increase due to continued funding in the field and the promotion of metagenomic technologies.

However, research on the gut microbiota in psoriasis remains imbalanced, with China and the United States leading the field. The United States surpasses most countries in citation frequency, with the highest-cited authors and most productive institutions, demonstrating its scientific strength in this area.

Although China has fewer citations than the U.S. and Italy, it excels in the number of publications. This could be attributed to the widespread and cost-effective use of gut microbiota sequencing technology in both countries, which encourages more research. China’s research output significantly increased around 2020, following the adoption of high-throughput sequencing technology.

The number of studies in China surged around 2020, coinciding with the widespread adoption of high-throughput sequencing technology. The introduction and popularization of metabolomics and the microbiome-skin axis, along with strengthened international collaboration, also contributed to increased research output in China. Additionally, during the COVID-19 pandemic, the relationship between the gut microbiota and the immune system and infection prevention and control became key areas of focus, leading to an increase in publications on gut microbiota research after the pandemic.

China’s research volume is growing, but its average citation count remains low, likely due to two factors: most publications are recent (post-2020), and regional, dietary, and ethnic factors may influence gut microbiota composition, prompting researchers to cite domestic data more often.

We identified the changing trends of hotspots and frontiers in psoriasis gut microbiota research by analysing keywords and cited references. In 2004, Ulpu Saarialho-Kere introduced the concept of the gut-skin axis, initiating the study of the relationship between skin diseases and the gut microbiome (Saarialho-Kere, 2004). Some researchers have observed in clinical practice that several inflammatory bowel diseases may be associated with skin lesions, suggesting a connection between the gut and the skin (Torres et al., 2013). The analysis of citation bursts reveals two distinct phases in the gut microbiome and psoriasis research. From 2013 to 2018, the literature primarily focused on the relationship between the gut microbiome and inflammatory diseases such as psoriasis and rheumatoid arthritis. These studies highlighted changes in the diversity of the gut microbiome, particularly the reduction of certain bacterial species (e.g., butyrate-producing bacteria), which may lead to immune dysregulation and systemic inflammation. From 2019 onwards, research shifted towards more detailed mechanisms, exploring the interactions between specific microorganisms and host genes, as well as how the gut microbiome influences the pathogenesis of psoriasis through immune pathways. Studies by Chang HH (2017) and De Pessemier B (2021), among others, discussed how host-microbe interactions regulate inflammatory responses. Collectively, these studies emphasize the close relationship between systemic inflammation in psoriasis and gut dysbiosis, with the latter exacerbating the disease’s inflammatory response. Recent research has increasingly focused on developing therapeutic strategies by modulating the gut microbiome.

In our study, the #3 pathogenesis described in the clustering visualization analysis outlines the research on mechanisms. Through the keyword co-occurrence network, we identified a key mechanistic map showing how changes in the gut microbiota influence the immune response in psoriasis. ( Figure 8 ).

In the timeline analysis, #0 precision medicine highlighted the therapeutic intervention potential of gut microbiota research. By summarizing the literature, we found that psoriasis patients’ gut microbiota changes are associated with the disease. Modulating gut microbiota could offer new therapeutic strategies for psoriasis (Widhiati et al., 2022; Zeng et al., 2024).