Background

Substance use and misuse are globally prevalent and remain an ongoing health crisis affecting every region of the world. In 2016, the United Nations Office on Drugs and Crime (UNODC) estimated that 275 million people aged 15–64 used drugs at least once [1], and the prevalence of drug use and drug use disorders has increased significantly in the period 2010–2016 [2]. Likewise, global alcohol consumption rates per capita had slightly increased over a 15-year period [3]. Regarding tobacco smoking, in 2015, 20.2% of the world’s population aged > 15 years old were current smokers [4]. As a result, substance use disorders caused approximately 20 million disability-adjusted life years (DALYs) and 8.6 million years of life lost (YLL) across regions and countries [5,6,7]. The World Health Organization (WHO) estimated that in 2016, drug and alcohol use disorders were responsible for respectively 160,235 and 145,565 deaths, which increased markedly from 1990 [8, 9]. These ongoing burdens are becoming great challenges for health systems of every country [2].

In the past decades, treatments of substance use disorders, both non-pharmacological and pharmacological methods, have been well-documented [10]. In terms of tobacco use, along with nicotine replacement therapies, non-pharmacological treatments such as “counseling”, “self-help”, and “behavioral therapies” have been proven as effective therapies that can maintain smoking cessation more than 6-month follow up [11, 12]. Similarly, non-pharmacological approaches including “skills training”, “cognitive behavior therapy” and “family and couple therapy” are used widely to improve alcohol dependence [13]. For drug use disorder, substitutional treatments including methadone, buprenorphine or naltrexone maintenance treatment are used commonly as replacement therapies, along with traditional medicine and motivational enhancement therapies [14].

Prevention and management of substance use disorder have been considered one of the top priorities. Internationally, the WHO and the United Nations have been at the forefront with many efforts in synthesizing evidence and developing guidelines and frameworks to combat this public health crisis [15,16,17,18]. There has also been an increasing focus on developing a standard set of indicators, which allow to build an optimal monitoring system for harm reduction interventions [19]. Despite these efforts, gaps in research, training, treatment, service delivery, and capacity building related to substance use disorder are recognized, with greater negative impacts on low-to-middle income countries [20]. Moreover, these challenges vary across regions and countries significantly. This heterogeneity requires contextually sensitive approaches to the development and implementation of ‘locally’ compatible policy solutions. This study attempts to ‘take stock’ of the currently available substance use literature through the use of bibliometric methods [21]. In literature, few studies using this method to investigate the current status and tendency of research publications in substance misuse in Saudi Arabia [22] or drug/cocaine addiction only [23,24,25]. This work aims to provide clinicians, policymakers and other stakeholders a better understanding of 1) the trend and the current focus of international research efforts regarding substance use disorders; 2) what evidence is currently available on related subjects; and 3) where research, evidence and service gaps remain ongoing challenges.

Methods

We used the Web of Science (WoS) to retrieve research publications focusing on substance use, comorbidity, treatment, and interventions. The WoS outweights other databases such as Scopus or MEDLINE. Initial, the WoS allows to extract information based on research disciplines that could not be done in other databases. Second, the WoS database comprises of leading and high impact scientific journals, while other databases included journals with a variety of quality [26,27,28]. Third, the WoS has a comprehensive coverage of scientific publications from 1900 until now with a diversity of research disciplines. Forth, the WoS has advantages in allowing to perform advanced search tool, refine the results to particular criteria, and evaluate the research productivity. This database offers a wide range of information about title, authors, keywords, sources/organizations, countries, languages, total citations as well as the average citation per literature. Our analysis focused on substance use disorder articles published from January 1st, 1971 to December 31st, 2017 in peer-reviewed journals. We did not include grey literature, conference proceedings, or books/book chapters in our analysis. Articles written in any language other than English were excluded.

Search strategy

Our search strategy was performed according to following steps:

Inclusion step

The literature from the WoS was retrieved using a set of search terms, focusing on 1) substance use disorder (including all illicit substances), 2) tobacco use, and 3) alcohol use disorder [29]. Synonyms for each search term were identified by research team including senior researchers (B.X.T and G.H.H) and junior researchers (C.T.N and N.B.N), whom had experiences in the field of substance use disorder. The keywords used were referred from previously published systematic reviews [30,31,32,33]. Our search query is outlined in Table 1.

Table 1 Search Query Text
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Exclusion step

We excluded articles which were 1) published later than 31 December 2017; 2) documents that were not articles such as book chapters and conference proceedings; 3) without author details; and 4) written in any language other than English. We also used the WOS database functionality to exclude publications in unrelated fields of study [see Additional file 1].

Data extraction

Data were exported from the WoS in text format and imported into Microsoft Excel for analysis. Exported data included: (1) Total number of publications by year for three types of substance use disorder (Illicit drugs, tobacco, and alcohol); (2) Name and details of journals; (3) Authors’ name, affiliation and number of publications; (4) Top cited articles; (5) Types of articles; (6) Title of the paper; (7) Year of publication; (8) Author’s and WoS’s keywords; (9) Number of citations of each article; and (10) Abstracts.

Data analysis

Our analysis of authorship involved an initial sorting of data based on the number of authors, total number of citations, citations per paper, h-index, and how many papers were written collaboratively [34]. We directly downloaded these data via the WOS Citation report.

We used search terms (see Table 1 (1), (2), (3)) using Microsoft Excel to quantify the volume of publications related to (1) drugs use disorder; (2) nicotine dependency; and (3) alcohol addiction. We then applied search terms (see Table 1 (4), (5), (6)) to determine the number of publications focusing on the following therapies and interventions: (4) Behavioral therapy OR Behavioral treatment, (5) Psychological treatment method, (6) Pharmacological therapy OR Pharmacological-treatment, and (7) Other treatment methods.

Next, we tracked the growth of publications in different substance use disorders. We used the period 5-year intervals across 1998 to 2017 to evaluate the “index of change” for each intervention. This measure shows a change of a research field by comparing the growth of publication of one period compared with that of previous one [35].

VOSviewer software (http://www.vosviewer.com/) was used to 1) create visualization graphs indicating contributions and collaborative efforts of sixty-one countries with at least five publications; 2) Visualizing the co-occurrence terms in titles and abstracts of all publications with at least 250 times of presence [36]. Networks highlighted the trend and provide the insight of the development of substance use disorders in our dataset at any level: node, connection, network and overall system [37].

Results

Table 2 illustrates general information of our dataset. This topic attracted the concern of research community that showed by the volume of publications increased markedly every 5 years, especially between 2013 and 2017 (one-third of all articles). Nearly 70% of the papers in all three methods was collaborative research of 2–3 authors and 4–6 authors, that is promised a main trend year after year, reflecting the multi-investigator in a research study [38]. Substance use disorder was the research field across disciplines, that was showed by half of the publication assigning to 2 or 3 research areas. The use of alcohol and tobacco is increasing rapidly in developing countries [39], however, most of the lead author are from developed countries (China was the only Asian country in the list of top 10 country of first author).

Table 2 General characteristics of selected articles
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Figure 1 reveals an acceleration of publications in the field of substance abuse disorder after 1990. The number of papers in this period accounted for approximately three-fourths of total number of publications. Noticably, the growth of publications was different among three types of substance use disorders (Table 3). The number of publications on Mindfulness and Digital medicine topics had the highest increase with more than 300% since 2003–2007 despite later presence than other methods. The number of papers on other non-pharmaceutical therapies (behavioral therapy, cognitive behavioral therapy, skills training or motivational interviewing) grew gradually, however, the growth rate was lower every 5-year period.

Fig. 1
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Number of papers by year in publication

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Table 3 Number of publication and the growth of publication (%)
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Table 4 presents that the Journal of Substance Abuse and Treatment was the most common journal with the highest number of publications (613 papers), followed by the Drug and Alcohol Dependence (591) and the Addiction journal (400).

Table 4 Research area and the Journal included the research area
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Table 5 shows information of 30 most prolific researchers. They published from 44 to 117 publications and had 1137 to 5878 citations. Among these authors, 25 (83%) had affiliations in the American institutions, while other authors worked at institutions in England, Italy and Canada.

Table 5 Most prolific authors
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Table 6 illustrates the research productivity among top 41 countries. The top five countries were North America (the United States of America and Canada), Europe (England and Italy), and Australia. The United States of America was the substance use disorder knowledge hub in the world, and ranked at the top of all indices and was the main collaborator of 38 countries in the list. There were 70% of research conducted in the U.S. as a result of national collaborations, whereas more than 40% of research projects in other countries were the results of international cooperation.

Table 6 Most prolific countries and the collaborations
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Strength of collaborative partnerships and contributions among countries are shown in Fig. 2. There were three major geographical research clusters including: 1) England, Scotland, Wales and Turkey; 2) East, and South-East Asia, such as The Peoples Republic of China, India, Taiwan, and Vietnam; and 3) Central and Eastern Europe, for example, Austria, Poland, and Bulgaria. This distribution might be justified by the geographical proximity and cultural similarity among countries in each cluster.

Fig. 2
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A global network of the 61 most prolific countries

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Figure 3 presents the most popular terms with at least 250 appearances drawn from the title and abstract, which could be separated into three topic clusters: 1) Intervention (Red), 2) Types of addictions: Tobacco addiction (Green), Drug addiction (Blue), Alcohol (Purple), and 3) Effects (Yellow).

Fig. 3
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Text (Title and abstract) mining

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Intervention

The word “Intervention” appeared the most with 9438 times appearances in papers focusing on smoking addition, followed by drug use and alcohol. Moreover, these papers presented intervention programs in different populations such as adolescents and students; and with a variety of methods such as training program, counseling, and motivational interviewing.

Types of addiction

“Smoker” and “smoking” frequently appeared alongside “withdrawal”. The term “pharmacotherapy” appeared in papers focusing on nicotine replacement and non-nicotine replacement. Papers with titles and abstracts that used the term “drug” also used the terms “intervention”, “problem”, or “disorder”. The term “alcohol” frequently appeared in studies on adolescents.

Effect

The term “effect” appeared 8640 times in the titles and abstracts, co-occurring with terms related to intervention/program or effects of “smoking”, “alcohol” and “drug” use on human health.

Discussion

This study provided an insight of global publications trend, research productivity and collaboration networks in the field of substance use disorder and treatment. In this study, we demonstrated a rapid increase of publications in the past few decades, especially papers focusing on mindfulness and e-health interventions. This growth was led by leading institutions located in the United States of America, United Kingdom, Europe, Canada, and Australia.

The current finding suggested that the number of publications about traditional intervention approaches such as behavioral therapy, cognitive behavioral therapy, or counselling raised gradually over years. This result was in line with previous reviews that these methods were the most common way in intervening alcohol, tobacco and drug-use disorder [40,41,42]. Moreover, we found a substantial shift toward the use of mindfulness and e-health interventions in this field. In literature, mindfulness interventions were effective in preventing alcohol relapse and decreasing withdrawal symptoms when compared with cognitive-behavioral treatment [43, 44]. Also, publications about digital medicine (or e-health) were found in all three types of substance use disorder. This intervention is delivered via computers or mobile phones, which enables to facilitate interactions between patients and clinicians. Although its long-term effects were limited, digital medicine was found to be useful when combined with human supports [45].

We found a pattern of collaborative research networks that showed a preference for geographical proximity and cultural similarity. Northern European countries (Norway, Finland, and Sweden), three countries in The United Kingdom (England, Scotland, and Wales) created a cluster in collaboration in research. Meanwhile, another cluster among the U.S., Japan and China (mainland), Taiwan (China), Vietnam, South Africa, India and Ukraine was generated. This can be explained by the strong international scientific collaboration between US, Japan and Asia countries. Moreover, health topics were major concern of those developing countries and received support from developed countries [46, 47]. These findings suggest the importance of increasing research capacity and establish collaborative partnerships between high income and developing countries.

There are several research studies and policy related implications derived from our findings. First, our study found there was an upward trend in the employment of mindfulness or digital medicine in the treatment of substance use disorder. Mindfulness and digital medicine, although confirmed to be effective, they are only trial with small sample size and have not been evaluated in a long-term research. Therefore, more research are needed to evaluate the outcomes of two treatment for substance use disorder [9]. Second, other systematic-review and meta-analysis focused the treatment of only alcohol dependence, tobacco dependence or drug use disorder. Our research using bibliometric analysis, thus, we could identify the global trend of all three kinds of substance use disorders and also highlight gaps in the scientific literature regarding contextual factors and multi-level sociobiological. Third, our findings suggest the need for international policy efforts that place priority on the development of research capacity in settings where substance use disorder is prevalent, frequently where the availability of relevant resources is simultaneously low. Some of the heavily cited papers in our study dealt with implementation science and patient outcomes. We suggest the promotion of evidence-informed policy making, health system strengthening, a renewed focus on sociobiological causes of substance use disorder, and recommend the consideration of technological transfers as potential long and short-term measures. This suggests a need for research policy that supports the examination of interventions that culturally adhere to different local contexts, specifically those that place priority on the collective when addressing substance use disorder within their communities.

This is the first bibliometric analysis of substance use disorder treatment literature. The use of bibliometric and similar approaches, like scientometrics and informetrics, have been used to monitor the trends in other research areas. Bibliometric analyses serve as a helpful tool for research managers and policy makers when setting priorities and identifying strategies for research development and public resource allocation. Previous systematic reviews and meta-analyses of substance use disorder interventions have largely focused on specific issues and combined outcomes of different treatment options. Thus, the implications of these reviews were intended to inform clinical practice and the design of intervention programs. Meanwhile, our study provides an overarching view of the changes that have occurred within the substance use disorder research agenda over multiple decades. The study of these general trends is useful for clinicians, researchers, program managers, and policymakers having the over-trend of the global development in treatment for substance use disorder people. However, the application of those methods in a country different from one country to another, especially between developing countries and developed ones. Social, culture and environment can be the factors contributes to increase the differences in policy application. For instance, in Vietnam, alcohol is consumed in traditional national holidays such as the Lunar New Year, or weddings, housewarmings, even in funerals, and death anniversary, especially in mountainous or rural areas. Moreover, alcohol is familiar part of business transactions [48] . National legal minimum age for on- and off premise sales of alcohol is 18 and 21 in Vietnam and the U.S., respectively. Therefore, there is a need for increasing the perceptions of potential harms caused by alcohol and tighten the minimum age of alcohol using. Government should get the priorities in investing more research in substance use disorder research and treatment, alongside the need to understandings local contexts.

The findings of this study should be viewed in light of its limitations. First, as the scope of our search on drug use was limited to opioid, drug, substance and marijuana, publications on other specific substances like Amphetamine-type stimulants (ATS) or other stimulants may not be covered, which may impact the thoroughness of our results and analysis. The breadth and comprehensiveness of our study may also be influence by the restriction on types of publications included - which consisted of only searchable peer-reviewed research articles and reviews, as well as on language of publications - the selected documents for synthesis were written in English and work produced outside academic institutions that were written in local languages was excluded. As for keywords, our analysis of their occurrence and co-occurrence may not fully reflect the full content of the articles they are attached to [see Additional file 1]. However, as a bibliometric analysis of large volume of publications, a summary of keywords is a helpful proxy for the overall contents of these papers.

Conclusions

Compared to other bibliometric analysis of substance use disorder, our bibliometric analysis offers a rare and comprehensive picture of the global efforts of substance use disorder and treatment. This study with the visualization of co-occurrence term in the titles and abstracts allows researchers to track connections among clusters, which is essential in identifying the global research trend. Researchers and policy makers can based on the results of this research to identify the future directions for research productions as well as the consider new therapy or prevention applying for the treatment of substance use disorder.