This study aims to map out the global research landscape on melatonin in the field of insomnia research from 2015 to 2024, following the BIBLIO list of bibliometric studies.

Two databases were searched: Web of Science Core Collection (WoSCC) and PubMed.

A comprehensive search strategy was developed for each database. See Supplementary File 1 for details.

Conference proceedings, abstracts, editorial materials, letters, collections, anthologies, news items, book chapters, and retracted publications.

Two independent reviewers screened all retrieved records based on titles, abstracts, and full texts. Disagreements were resolved through consensus or by a third reviewer. A PRISMA-style flowchart ( Figure 1 ) summarizes the screening process, including the records retrieved from each database and the stepwise exclusion steps, ultimately determining the final set of included literature.

Data is exported from the database in the “txt” format, with file names that start with “download_*.txt.” Citespace (6.3R1) and Vosviewer (1.6.20) tools are then used to analyze the files and search for keywords, references, publications, nations, institutions, journals, co-cited journals, authors, and co-cited authors.

CiteSpace’s parameters were set as follows: (1) 2015–2024-time frame; (2) node type selection at a time; (3) g-index selection of k-value set to 25; and (4) Top N option set to 50. Nodes in a CiteSpace network knowledge graph stand for the informational unit of the object under study, and node sizes indicate how frequently an event occurs. The time and quantity of the examined items are indicated by the color and breadth of the “year rings” inside the nodes. On the other hand, a high degree of intermediate centrality throughout the whole network is shown by the purple outside rings. The degree of correlation between the various factors under analysis is shown by the thickness of the connecting lines.

Since it represents the general trend of development in this field of study, the number of publications per year is very important. The publication volume of research articles about melatonin and insomnia over the last ten years can be broken down into three phases, as seen in Figure 2 . Although there were comparatively few publications during the first phase, which lasted from 2015 to 2018, there was an overall upward trend. The number of publications steadily rose from 99 to 159 during the second phase, which spanned 2019 to 2021. The number of publications peaked during the third phase, which ran from 2022 to 2024. In 2022, the number of articles about melatonin and insomnia peaked at 159, making it the year with the most publications in this area in the previous ten years. A linear trend line was created for annual publications in order to better understand the output trend. This resulted in the equation Y=11.964X-24052, where Y stands for annual publications and X for the year. The coefficient of determination (R²) for the model is 0.9283. Overall, the number of articles about melatonin’s role in insomnia has been rising steadily, which is indicative of the topic’s increasing significance and popularity.

Open VOSviewer 1.6.20, Import the search results, and examine the countries’ co-occurrences. Research on this subject was conducted in 428 different countries. A national-level collaboration network with a minimum of five publications is depicted in Figure 3A . With a total link strength of 900, the results show a co-occurrence map of 34 countries, demonstrating strong international cooperation. With a total link strength of 216, the United States is at the center of the collaboration network and demonstrates extensive international collaboration. The United Kingdom and the United States have the closest collaboration with other nations. With a total link strength of 153, the UK demonstrates high centrality as well. Comparable node sizes between China and the US suggest similar publication volumes. The network has seven clusters, including the Asia-Pacific cluster, which is represented by China, Australia, and Japan, and the European cluster, which is represented by France, Italy, and Switzerland.

Table 1 highlights the top 10 countries by number of publications and looks at their publication volume, citation rates, and link strength. In terms of publications, the United States leads with 300, followed by China with 167 and the United Kingdom with 90. The United States received 8,153 citations, followed by the United Kingdom (3,968) and Italy (3,286). Germany had the highest average citation rate (46.02), followed by the UK (44.01) and France (43.69). The United States dominates this field of study, as evidenced by the national analysis, which shows that it leads in both publications and citation rates. China has 167 publications, which puts it in second place, but its citation rate is lower than that of other countries, indicating that output volume and research influence are not always related. In terms of average citation rates, European nations—including the UK, Germany, Italy, and France—perform better than Asian nations.

A total of 2,465 institutions contributed to the publication of articles on this subject, according to the data that was retrieved and imported into Vosviewer 1.6.20 for institutional analysis. The collaborative network at the institutional level is depicted by Figure 3B , which shows 92 institutions. The institutions’ close cooperation is indicated by the total link strength of 3,382. Sapienza University, University of Pisa, University of Southampton, Johns Hopkins University, and University Hospital of Strasbourg are among the top five universities based on link strength analysis, which shows that their links are thicker. Europe has a cluster advantage in melatonin research, as evidenced by the fact that three of these institutions are European. Harvard Medical School (692) is in second place, followed by the University of Surrey (634) in third place, and the University of California, San Francisco (1079) is at the top among citation rates.

Each of the top 10 institutions in terms of publication volume has published more than 11 papers, as shown in Table 2 . The top three universities are Harvard Medical School (21 publications), Monash University (18 publications), and Sapienza University (15 publications). A total of 143 articles were published by these top 10 institutions, making up 13.2% of all publications. It is noteworthy that Harvard Medical School has a high average citation rate and publication volume.

For journal analysis, the obtained data was imported into Vosviewer 1.6.20, which revealed that 488 journals had published these kinds of articles. Figure 4A shows the collaboration networks of 43journals. In total, the top 10 journals published 185 papers, or 17.07% of all publications, as shown in Table 3 . Out of all of these, SLEEP MEDICINE ranked first and published the most studies (n = 31). Frontiers in Psychiatry came in second with 25 studies, and JOURNAL OF SLEEP RESEARCH came in third with 21 studies. Indicating that the caliber of publications in this field of study is low, two of the top ten journals had Impact Factors (IF) higher than five, while the average for the remaining journals was three. Of these, the journal Sleep Medicine Reviews is at the forefront of its field, as evidenced by its highest IF of 11.2 and Q1 zone ranking in the JCR classification. This indicates that the journal is well-known among researchers and has a high degree of academic standards and influence in its field. With a JCR classification ranking in the Q1 zone and an IF of 5.3, SLEEP comes next.

Examine the co-cited journals after importing the search results into VOSviewer 1.6.20. This suggests that a total of 6,096 journals is writing about this subject. Figure 4B : Nodes that are cited sources in the research field literature are represented by the 399 journals that are shown. The number of citations is indicated by the size of the node, the larger the node, the greater the influence and the number of citations. A stronger co-citation relationship is indicated by thicker connecting lines, which show how frequently two journals are cited together in the same article. Six clusters are created from the data; these clusters show the outcomes of the journal citation clustering process. Similarly colored journals tend to represent a discipline or field and have more similar citation patterns. The top ten journals in terms of co-citation frequency are listed in Table 4 . Among these, Sleep has the highest total citation rate (2,310), followed by Sleep Medicine (1,414) and Sleep Medicine Reviews (1,295). Indicating that the field is still in a steady accumulation phase, the majority of impact factors are concentrated in the 3–5 range. The fact that Sleep Medicine Reviews has a high single-article influence but a small publication volume is reflected in its impact factor of 11.2 and third-place citation rate. Due to their higher publication volumes, Sleep and Sleep Medicine achieve higher total citation counts, despite having impact factors of 5.3 and 3.8, respectively.

A total of 4,854 authors took part in this study, according to the data imported into VOSviewer 1.6.20 for author analysis. The top ten authors and the authors who receive the most citations are listed in Table 5 according to the number of articles they have written. Of them, Ferri R and Zisapel N tied for third place with 11 articles each, while Bruni O leads with 17 articles, followed by Palagini L with 15. Citation counts showed that Zisapel N had the most citations (645), followed by Bruni O (551) in second place and Malow B. A (347). in third. Interestingly, Bruni O has a high citation rate and a large number of publications, which suggests that her work is of high quality in this field of study.

Figure 5A illustrates author collaboration by grouping 34 authors into 5 clusters. Aguglia E, Biggio G, Geoffroy P. A., Girardi P, Grassi L, Manni R, Minervino A, Nobili L, Palagini L, Philip P and Plazzi G are among the authors working together in the same cluster. The grouping of co-cited authors is shown in Figure 5B . The brightness of each color corresponds to the frequency of citations; the higher the frequency, the brighter the hue. This allows for the easy identification of the most frequently cited authors among the 21,350 co-cited authors, of which 232 are displayed. The author with the closest ties to other authors is Morin C.M.

A keyword visualization analysis was performed using Citespace. This study’s co-occurring keywords visualization analysis diagram has 451 nodes and 776 links, with a network density of 0.076 ( Figure 6A ). Sleeplessness (475), melatonin (279), circadian rhythm (166), double blindness (111), quality of life (100), bright light therapy (90), prevalence (85), sleep (79), efficacy (71), and children (61) are among the top 10 keywords. “Insomnia” was the most frequently occurring of the high-frequency keywords found, with 475 occurrences, indicating its importance as a worldwide health concern in sleep medicine research. The three primary components of the research network, “circadian rhythm” (166 occurrences) and “melatonin” (279 occurrences), came in second and third, respectively, underscoring the crucial role of the melatonin system in insomnia. According to frequency analysis, insomnia is still a global problem and a research hotspot, as Table 6 illustrates, with “body temperature” having the highest centrality (0.16). An important focus area in the field is represented by a node with a centrality value >0.1, which denotes the node with the greatest attention and influence in the research field. In the future, body temperature rhythms could be a novel approach to treating insomnia because they are a significant biomarker of circadian rhythm function and have special significance in diagnosing insomnia that is disordered by the circadian rhythm. Additional keywords that have centrality values greater than 0.1 are “double-blind” (0.12) and “quality of life” (0.11), which highlight the significance of patient-reported outcomes and methodological rigor in this area.

The keyword cluster visualization analysis is displayed in Figure 6B after the data was imported into Citespace (version 6.3 R1). As demonstrated by the results, the modularity Q-value has a distinct and significant clustering structure, surpassing the 0.3 threshold at 0.697. Furthermore, it was found that the clusters’ average contour value was 0.86, suggesting that this unique clustering technique is dependable and reasonable. A total of seventeen clusters were produced using various clustering labels: #0 circadian rhythnm sleep disorders, #1circadian rhythnm, #2activation, #3older adults, #4parkinsons disease, #5physical activity, #6restless legs syndrome, #7children, #8alzheimers disease, #9autism spectrum disorder, #10case report, #11sleep duration, #12seizure frequency, #13gut-brain axis, #14electroacupuncture, #15melatonin suppression, #16melatonin receptors.

Classify the above keyword cluster tags, where tags such as #0 circadian rhythm sleep disorders, #4 Parkinson’s disease, #6 restless legs syndrome, #8 Alzheimer’s disease, and #9 autism spectrum disorder are associated with insomnia comorbidity. Tags such as #1 circadian rhythnm, #13 gut-brain axis, #15 melatonin suppression, and #16 melatonin receptors are related to the mechanisms of insomnia. #2 activation, #14 electroacupuncture, and #5 physical activity are related to intervention or treatment methods. #3 older adults and #7 children are related to the population with insomnia. #10 case report and #11 sleep duration are outcome measures related to insomnia.

Select the cited references for visualization analysis after importing the data into CiteSpace (version 6.3 R1). Figure 7A illustrates this, with a network density of 0.0108 and 249 nodes and 333 links. Gringas P. (2017), Sateia M.J. (2017), Maras A. (2018), Riemann D. (2017), Zisapel N. (2018), and Bruni O. (2015) are among the top five cited references by citation count, as shown in Table 7 . Elrod MG, 2015 (0.19), Bruni O, 2018 (0.17), Goldman SE, 2014 (0.21), Chang YS, 2016 (0.29), and Auger RR, 2015 (0.17), are the top five references in terms of centrality, as shown in Table 8 . Chang YS, 2016 (0.29), which was published in Jama Pediatrics, is noteworthy for having a high article quality, ranking first in centrality, having an IF of 24.7, and being in JCR Zone 1.

Twenty-four sudden terms were found by performing an abrupt analysis of the keywords in the chosen literature ( Figure 7B ): Keywords like “autism spectrum disorder” (intensity 3.36), “circadian rhythm phase” (intensity 2.59), and “suprachiasmatic nucleus” (intensity 2.4) emerged between 2015 and 2017, indicating a growing interest among researchers in the connection between circadian rhythm mechanisms and neurological disorders. From 2016 to 2019, the increasing depth of clinical application research was reflected in the persistently high heat of keywords like “neurodevelopmental disorders” (intensity 3.54) and “sustained-release melatonin” (intensity 3.12). A trend towards the integration of sleep medicine with oncology, psychiatry, and pain medicine is evident in the rise of new hotspots like “mental disorders” (intensity 3.48), “breast cancer” (intensity 3.53), and “chronic pain” (intensity 2.45) after 2020.

A total of 4,854 authors contributed to the 1,084 publications from 428 countries, 2,465 institutions, and 488 journals that were examined in this study. According to the analysis, there are three primary stages to annual publications. A comparatively small number of publications were published during the first phase, which ran from 2015 to 2018. The majority of the research was centered on controlled trials investigating the potential benefits of melatonin for treating insomnia as well as the relationship between melatonin and insomnia. To evaluate the therapeutic efficacy of melatonin, randomized controlled trials were carried out on a range of populations, including adults, children, the elderly, and perimenopausal women. The number of publications stabilized and exhibited an overall upward trend during the second phase, which lasted from 2019 to 2022. By measuring melatonin secretion levels, the primary research found that acupuncture, traditional Chinese medicine, and cognitive behavioral therapy were effective in treating insomnia. The third phase, which lasted from 2022 to 2024, saw a high volume of publications. The year with the most publications was 2022. By 2022, melatonin’s effectiveness as a treatment for insomnia had been mainly established; however, more research was required to determine whether it applied to patients with particular illnesses. A comparable number of publications were published in 2023 and 2024, with more researchers concentrating on the connection between melatonin and insomnia in relation to neurological disorders.

Geographically, the United States accounted for 27.7% of all publications with 300 publications, and the country had the highest total number of citations with 8,153. With 167 publications—or 15.4% of all publications—China came in second, with a total citation rate of 2,091, demonstrating the US’s considerable influence in this area.

The Institutional Collaboration Network reports that two of the top 10 institutions are from the United States, two are from the United Kingdom, two are from Italy, and two are from Australia. In comparison, although China ranks high in the total number of publications in this research field, the number of publications from each institution is relatively low, indicating a lack of continuity among Chinese institutions in the research on the correlation between melatonin and insomnia. Sapienza University of Rome, Harvard Medical School, and Monash University are the top three universities. It is important to remember that hospitals and universities make up the majority of these institutions. It is worth noting that Sapienza University of Rome is located in Italy, which ranks fourth in terms of publication volume, indicating that the University of Rome has extensibility in this field of research. In the citation analysis, the University of California, San Francisco ranks first with 1,079 citations, but only seven publications, indicating that this institution has high-quality publications.

Following an analysis of the authors, Bruni O is in the lead with 17 published pieces, followed by Palagini L in second place with 15 articles, and Ferri R and Zisapel N in a tie for third place with 11 articles apiece. The majority of Bruni O’s published works discuss children and examine how well melatonin works to cure sleeplessness in young patients. In his essays, Bruni O analyzes childhood insomnia from several angles, including its main symptoms, diagnosis, and treatment options. 97.4% of pediatricians prescribe melatonin to children with chronic insomnia, with 87.3% of patients being between the ages of one and two, according to an online poll on the topic. Of the patients, 42.5% were between the ages of 10 and 18, and 62.1% were between the ages of 2 and 5 (13). The main focus of author Palagini L’s work was creating professional practice recommendations for hypnotic drugs. She also employed systematic reviews to examine the effectiveness of melatonin in treating adult insomnia. The classification of insomnia and its physiological and pathological phases were the main topics of author Ferri R’s research. She summarized the effectiveness of medicine and cognitive behavioral therapy as treatments for insomnia. It was discovered that Ferri R and Palagini Lworked closely together, and their research topics were very relevant to one another.

An analysis of the results of co-cited authors revealed that Bruni O, Malow B.A, Gringras P, and Cortese S were the next most frequently mentioned authors. The main topic of author Zisapel N’s publications is melatonin’s function in regulating circadian rhythms and human sleep. The study cohort comprised children with neurodevelopmental problems, people with Alzheimer’s disease (AD), and those with jet lag from shift work (13). While children are the primary focus of Malow Beth A’s melatonin study, she also points out that sleep problems are linked to a number of neurological illnesses and are frequently brought on by the overlapping interplay of genetic, neurobiological, and environmental variables. Insomnia or hypersomnia are common symptoms of these diseases (14). Assessments of children with autism spectrum disorders’ behavioral skills and quality of life, as well as the effectiveness of melatonin in treating sleep issues, are the main areas of research for author Gringras P. Children with attention-deficit/hyperactivity disorder (ADHD) and teenagers with neurodevelopmental issues can benefit from melatonin treatment, according to Cortese S’s major research on the topic.

Sleep Medicine is the most prolific journal, according to journal analysis, with 29 articles and 680 citations overall. This suggests that the publication has made significant contributions to the study of melatonin and insomnia. With 2,310 citations, SLEEP is the most referenced journal. With 92.47 average citations, the Journal of Sleep Research has the most citations of any journal. Frontiers in Psychiatry, Journal of Clinical Sleep Medicine, Journal of Sleep Research, Sleep Medicine Reviews, International Journal of Circadian Rhythms, Nature and Science of Sleep, Sleep, International Journal of Environmental Research and Public Health, and Journal of Affective Disorders are the top ten journals in terms of publication frequency. Despite not having the highest publishing volume, Sleep Medicine Reviews (IF = 11.2), which is categorized as Q1 in the JCR, has the highest average number of citations among them, suggesting that higher article quality is associated with higher citation rates. This provides melatonin therapy for insomnia with a strong theoretical underpinning and data study background. With impact factors greater than 5, the top three journals in terms of publishing frequency are Journal of Clinical Sleep Medicine (IF = 3.5), Frontiers in Psychiatry (IF = 3.2), and SLEEP MEDICINE (IF = 3.8). This implies that the caliber of publications in this field of study needs to be raised, and more focused research ought to be done in order to publish in reputable journals and increase their impact.

According to the frequency of citations, the top five references were Gringas P. (2017), Sateia MJ. (2017), Maras A. (2018), Riemann D. (2017), Zisapel N. (2018), and Bruni O. (2015). We discovered that the top five papers among these comprise evaluations of the current state of melatonin use, clinical practice guidelines, and clinical trial research. More impartial proof of melatonin’s effectiveness in treating insomnia can be found in clinical trial studies. In order to treat insomnia in children and adolescents with autism spectrum disorder (ASD), a unique formulation of prolonged-release melatonin minitablets (PedPRM) that is appropriate for pediatric use was tested with a placebo in (Gringas P, 2017). PedPRM was reported to be safe and effective for treating insomnia in children and adolescents with ASD after 13 weeks of double-blind treatment, regardless of whether they also had neurodevelopmental disorders (NDDs) or attention deficit hyperactivity disorder (ADHD) (15). Melatonin drugs have been included in clinical practice recommendations for the treatment of adult chronic insomnia, according to (Sateia MJ, 2017), and cognitive behavioral therapy has been established as the standard treatment strategy in addition to medication (16). A sleep history, the use of sleep questionnaires and sleep diaries, and other moderate- to high-quality evidence should all be considered in the diagnosis of insomnia, according to Maras (2018). Adults with chronic insomnia are advised to begin treatment with cognitive behavioral therapy (17). Cognitive behavioral therapy is mentioned in both guidelines, suggesting that it has emerged as the mainstay of treatment for insomnia. Melatonin, a circadian rhythm cue, has been shown to impact circadian rhythms, restore sleep duration in older adults, and encourage sleep anticipation in the brain’s default mode network (DMN) (Zisapel N, 2018). In patients with Alzheimer’s disease (AD), exogenous melatonin can enhance cognitive decline and cardiovascular health (16). Melatonin’s usage in treating pediatric mental illnesses is the main topic of discussion in Bruni O. (2015). It has been observed that children are now the main demographic impacted by insomnia (18). Notably, Gringas P (2017), and Riemann D (2017), both of whom had impact factors greater than 5, showed that exogenous melatonin has a substantial therapeutic effect on insomnia, offering excellent theoretical justification for its use in treating insomnia.

Chang YS, 2016 (0.29), Goldman SE, 2014 (0.21), Elrod MG, 2015 (0.19), Bruni O, 2018 (0.17), and Auger RR, 2015 (0.17), are the top five centrality rankings of the mentioned references. The article at the center of the cited literature is indicated with the highest centrality. Based on a randomized clinical trial, the cited reference Chang YS (2016) showed that melatonin administration is a safe and efficient way to improve children with Atopic Dermatitis (AD)’s sleep latency and disease severity (19). With an Impact Factor (IF) of 24.7 and a ranking in the top quartile (Q1) of the Journal Citation Reports (JCR), this article’s publication in JAMA Pediatrics demonstrated its authority. Melatonin’s function in children with ASD was examined by Goldman SE, 2014 (0.21) and Elrod MG, 2015 (0.19), both of which confirmed that ASD is a mental illness linked to symptoms of insomnia (20, 21). Melatonin is the safest alternative for children with NDDs, according to growing data (22). The American Academy of Sleep Medicine’s Clinical Practice Guidelines support the use of timed melatonin in treating children and adolescents with delayed sleep-wake phase disorder (DSWPD), but more research is required to determine its suitability for use in adults and the elderly (Auer RR, 2015, 0.17). Notably, three diseases—ASD, NDDs, and DSWPD—are included in the top five most cited references. All of these illnesses are linked to sleeplessness in one way or another, and insomnia is very common.

Current research trends are somewhat reflected in the examination of the quantity of citations for keywords in this field. Future study in this area will likely focus on the integration of insomnia with pain management, psychology, and oncology. Surveys show that between 29 and 75 percent of cancer patients suffer from sleeplessness, which lasts the duration of the illness and treatment (45). The bidirectional relationship between insomnia and cancer can now be explained by a number of molecular mechanisms, such as hypothalamic-pituitary-adrenal axis dysfunction and cytokine dysregulation (46). As a result, addressing insomnia benefits both long-term cancer survivors and people receiving ongoing cancer treatment. This reciprocal association raises the possibility that prompt sleep intervention could be a novel cancer treatment target (47). According to studies, melatonin supplements can help breast cancer patients with their sleep issues while also increasing the sensitivity of chemotherapy medications and lowering their adverse effects (48). Melatonin can help with sleeplessness in neurological conditions such as Alzheimer’s disease (AD), Parkinson’s disease (PD), epilepsy, stroke, and restless legs syndrome (RLS). It is also involved in neuroprotection, mood modulation, antioxidant activity, and other brain activities (49–52). Up to 48% of people with chronic sleep difficulties may have sleep disorders (53). While poor sleep quality might worsen sleep-related pain and pain spread (54), research shows that long-term treatment of sleep problems can alleviate physical pain and may avoid chronic pain disorders in insomnia patients (55). Melatonin enhances analgesic effects by blocking nociceptive signal transmission through MT1/MT2 receptors in the spinal dorsal horn. Melatonin and its receptor agonists have demonstrated good efficacy in treating insomnia in fibromyalgia, according to clinical investigations, underscoring their potential to reduce pain, promote better sleep, and improve quality of life (56). To fully utilize melatonin’s therapeutic potential in neurological illnesses, pain-related problems, and oncological diseases, future studies should concentrate on how it works in concert with other forms of treatment. Research tactics should include encouraging high-quality systematic reviews that incorporate evidence and guide practice and supporting international multi-center collaborative projects. The pathophysiological pathways that sleeplessness and other comorbidities share should be further studied. High-quality data should be concentrated on certain populations, such as older people with neurodegenerative diseases and children with neurodevelopmental abnormalities, when converting findings into therapeutic practice. Instead of replacing CBT-I, melatonin should be marketed as an additional or supplemental treatment. Stress that melatonin should be used appropriately in clinical settings as a “circadian rhythm regulator” as opposed to a “sleep aid.” Regulatory bodies could think about turning melatonin into a medicine for management and enforcing stringent labeling laws to guarantee precise dosage and clear information. Government departments should also set up a nationwide monitoring system while formulating policies.