Abstract
Research on conspiracy theories in digital media has grown considerably in recent years. As a result, the field of research has become more multidisciplinary and diverse. To bridge disciplinary boundaries, identify foci of analysis and research gaps, this study provides an interdisciplinary systematic literature review (2007–2020), analyzing current research on conspiracy theorizing online, both quantitatively and qualitatively. Findings show that the majority of studies lack a definition of conspiracy theories and fail to conceptually delineate conspiracy theories from other forms of deceptive content. We also found that while the field employs a variety of methodological approaches, most studies have focused on individual, “mainstream” social media platforms, “Western” countries, English-language communication, and single conspiracy theories. We use the findings of our review to remedy conceptual and empirical shortcomings and to provide suggestions on how to move forward in research on conspiracy theories online.
Keywords
Introduction
Conspiracy theories—defined as alternative explanations of historical or ongoing events claiming that people or groups with sinister intentions are engaged in conspiratorial plotting (Uscinski, 2018)—have permeated online communication (Wood and Douglas, 2015), news media coverage (Waisbord, 2018), popular culture (Bell and Bennion-Nixon, 2000), and political rhetoric (Mede and Schäfer, 2020), among other fields.
For a long time, conspiracy theories were perceived as harmless phenomena that were “silly and without merit” (Keeley, 1999: 109) or only existed as “‘soft’ beliefs” (Sunstein and Vermeule, 2009: 220) that people quietly kept but rarely acted upon. Profound changes in the media and platform ecosystem and particularly the advent of social media platforms, which have enabled faster communication about and dissemination of conspiratorial narratives, have changed this, however. Thus, the last few decades have seen a plethora of “high-profile conspiracy theorizing” (Uscinski, 2018: 233) around topics such as vaccination, climate change, the 9/11 attacks (Mahl et al., 2021), or, most recently, the COVID-19 pandemic (Zeng and Schäfer, 2021).
As a result, research on conspiracy theories in digital environments has grown across disciplines and become more diverse in terms of concepts, analytical approaches, and method(ologie)s. Against this backdrop, the contribution of this article is twofold. First, we
Research on conspiracy theories in online environments
The genesis of a research field
Starting with Hofstadter’s (1965) foundational work on conspiracy theorizing as the manifestation of a “paranoid style,” distinctive strands of research have emerged, now spanning half a century and a multitude of disciplines (for overviews, see Butter and Knight, 2015; Uscinski, 2018). While historical approaches have investigated structural and historical features as indicators of societal crises (e.g. Davis, 1971; Wood, 1982), cultural, philosophical, and epistemological accounts have explored what defines conspiracy theories and their epistemological characteristics (e.g. Clarke, 2002; Knight, 1999). Socio-psychological and political approaches, by contrast, have focused on individuals, aiming to identify factors that drive people to adopt conspiratorial beliefs (e.g. Swami et al., 2010; Wood and Douglas, 2013).
In recent years, triggered by the advent of digital technologies, the visibility of conspiracy theories has increased. The architecture of online environments, such as technological affordances of social media platforms, has facilitated the dissemination of conspiratorial narratives, for instance, by circumventing traditional and institutionalized gatekeepers. This allows conspiracy communities to emerge and grow over time. In turn, the increased visibility of such content encourages more individuals to publicly share their support and to connect with like-minded people (cf. DeWitt et al., 2018). These shifts in digital ecosystems have led to the emergence of a new research field: information- and communication-related studies interrogating the interplay between conspiracy theorizing and digital media, that is, online (news) media, social media platforms, and instant messengers (e.g. Theocharis et al., 2021; Tingley and Wagner, 2017).
A closer look at scholarship on conspiracy theories online points to two constituting characteristics. First, a
Second, the field is characterized by
The necessity of an interdisciplinary literature review
Due to the growing number of studies on conspiracy theories in online environments and the broad thematic, conceptual, methodological, and disciplinary spectrum that they represent, it has become difficult to keep track of all research activity. In such situations, systematic literature reviews integrating insights from different research strands and disciplines, identifying analytical foci as well as blind spots and limitations in current work, can help. They can consolidate knowledge in a field of research and foster scientific progress—and in this case, help to fully comprehend how conspiracy theorizing interacts with digital media.
The article at hand provides such a systematic review. We start with investigating the multi- and interdisciplinary character of research on conspiracy theories online and the field’s development over time. Thus, our first research question (RQ1) reads,
Second, we are interested in whether and how conspiracy theories are defined and delineated from other forms of deceptive content, and how conspiracy theories are conceptualized. This leads to our second research question (RQ2):
In addition, we map the empirical assessment of prevalent conspiracy theorizing online, that is, conspiracy theory topics, online environments, countries and languages, methodological approaches, and the main research objects under investigation. Hence, our third research question (RQ3) asks,
Data and methods
Literature search and sample
To identify relevant publications, we used Scopus, one of the most comprehensive scholarly databases covering a wide range of disciplines. Compared to the Web of Science database, Scopus also includes edited volumes, book chapters, and conference proceedings (Mongeon and Paul-Hus, 2016). At the same time, it is less inclusive than Google Scholar, which also contains (under)graduate theses or conference presentations (Gusenbauer and Haddaway, 2020).
We performed a database search including all publications (i.e. journal articles, books, book chapters, and proceedings) that contained the following search terms in the title, abstract, or keywords:

Literature selection process.
After this, all articles were checked in detail by screening the abstracts and critically assessing the full texts according to the following two
Literature categorization and coded variables
With respect to RQ1, the first set of variables was used to assess the field’s evolution over time and across disciplines (for a detailed overview of all variables, see Supplementary Material Table B1). For each article, we coded the
The second block of variables aimed at conceptual approaches (RQ2) and covered whether a
A third set of variables was only coded for empirical studies. Our interest in empirical-methodological approaches (RQ3) spanned the analyzed
Intercoder reliability calculation regarding the above-mentioned variables was carried out by two coders using a random sample of 15 articles (approx. 10%) and showed very good reliability scores (Krippendorff’s α ⩾.83; see Supplementary Material Table B1).
Results
In line with our research questions, this chapter is divided into three subsections: We start with the development of the research field (
The research field over time and across disciplines
Rising academic attention
A look at the distribution of articles over time shows a sharp increase in academic attention to conspiracy theories online across all disciplines—with the last 2 years accounting for more than half of all publications dealing with the issue since 2007. As Figure 2 illustrates, only very few articles appeared between 2007 and 2017, followed by a first slight rise in 2018 and 2019, and a sharp 180% increase in 2020 over the previous year. Likely, this growth is backed by the high proliferation of conspiracy theories online during the COVID-19 pandemic.

Number of studies investigating conspiracy theories online.
Mostly empirical studies
The overwhelming majority of publications are empirical analyses (87.2%). In contrast, only 6.1% introduce a novel methodological approach, for instance, to automatically detect conspiracy theory-related content (Samory and Mitra, 2018bA; Conti et al., 2017A) 4 . Overall, 4.1% of all publications primarily aimed to make a theoretical-conceptual contribution while still empirically examining data—such as Neudert et al. (2019A), who introduced an empirically grounded typology of political news and information on social media and compared sourcing and consumption during three elections. A very small minority of 2.7% of publications were entirely theoretical or conceptual in nature—outlining frameworks such as the “anti-public sphere,” an online space which includes conspiratorial or alt-right content (Davis, 2021A).
High multi- and interdisciplinarity
Our review reveals that research on conspiracy theories in online environments spans a multitude of disciplines. We aggregated them into social sciences (40.5%) and information science (17.6%), which were the most prominent, followed by life sciences and medicine (10.8%), arts and humanities (8.1%), and law (0.7%). Taking a closer look at the multidisciplinarity of the field, we found that 33.9% of all articles were published in monodisciplinary journals outside of the respective authors’ main discipline. Here, disciplinary differences appeared: While social scientists published most frequently outside of their field (16.5%), for instance, in life sciences journals about health-related conspiracy theories, life scientists strictly stayed within their disciplinary boundaries. Information scientists (8.7%) and humanities scholars (7.8%) mainly chose social scientific journals as outlets. Across disciplines, 5.2% of all studies were published in multidisciplinary journals such as
With respect to the interdisciplinarity of the field, our findings point toward a high degree of collaboration across disciplinary boundaries: 41.9% of all studies include authors from at least two disciplines. However, most of these collaborations stayed within the same broader research tradition, for example when social scientists from communication science and sociology work together.
Conceptual perspective
Lack of definitions, but agreement on basic conceptual elements
Turning toward the conceptual perspective of conspiracy theories, our research shows that among the 148 articles coded, only 38.5% provided a definition of the term “conspiracy theory.” Therefore, most of the articles in our sample studied conspiracy theories online
The studies that did provide such a definition, however, agree on specific foci and conceptual elements of conspiracy theories (see Figure 3). Most of these definitions emphasized the content of conspiratorial narratives (93%) by defining them as “an allegation regarding the existence of a secret plot between powerful people or organizations” (Chen et al., 2020b: 1344A following Wood and Douglas (2015)). In contrast, 17.5% highlighted the function of conspiracy theorizing, as they “reduce the complexity of reality” (Mocanu et al., 2015: 1198A) or “‘help’ people make sense of the world” (van den Bulck and Hyzen, 2020: 45A). Only 5.3% accentuated the context in which conspiratorial narratives emerge by stating that they arise from people’s “desire to understand critical events occurring in the society” (Andrei et al., 2019: 1433A, following van Prooijen and Douglas (2017)).

Foci and conceptual elements of definitions.
Looking at frequently used conceptual elements to define conspiracy theories, studies often referred to responsible, often secretly operating actors (61.4%) or historical events or practices (47.4%). Others pointed out that conspiracy theories provide alternative explanations that run counter to official accounts (29.8%) or point to the goals (24.6%), actions (10.5%), or targets (10.5%) of conspiracy theorizing. The majority of articles defined conspiracy theories using several of these elements, with the following occurring most often together: actors and events (24.6%), actors and their goals (10.5%), events and alternative explanations (5.3%), or events, actors, and goals (5.3%).
Of the 57 studies that provided a definition, 68.4% relied on definitions introduced in prior scholarship. The definition cited most often in our sample (8.7%) was the one by Sunstein and Vermeule (2009: 205), who understand conspiracy theories as “an effort to explain some event or practice by reference to the machinations of powerful people, who attempt to conceal their role”—which largely corresponds with the most frequently used conceptual elements found in our analysis.
Blurred conceptual boundaries
Scholars have criticized that conspiracy theories and other forms of deceptive content such as mis- and disinformation are often not delineated in a meaningful way (Schatto-Eckrodt et al., 2020; Uscinski, 2018; Zeng, 2021). Our results empirically support this concern: 72.3% of all studies examining conspiracy theories also refer to or mention the concepts of misinformation, disinformation, fake news, or rumors
Lack of theoretical frameworks
Although the multidisciplinary nature of the research field suggests that the analyses would use a wealth of theoretical and conceptual frameworks, our results indicate otherwise. First, only 34.5% of all studies explicitly embedded their empirical investigation in a theoretical or conceptual framework at all, for example, by deriving research questions, hypotheses, or analytical dimensions from an established or newly developed conceptual framework. Many of them provide a brief summary of empirical findings from prior research—which is certainly valuable, but lacks sufficient theoretical reflection, may make generalization beyond the analyzed cases more difficult, and could even produce empirical artifacts. Second, studies which did name theoretical or conceptual frameworks mainly used work from the social sciences, such as the health believe model (e.g. Briones et al., 2012A), framing (e.g. Yang et al., 2014A), or motivated reasoning (e.g. Bode and Vraga, 2018A). It should be noted that these results may be due to different disciplinary traditions. Thus, it seems that theoretical and conceptual frameworks are used more frequently in the social sciences than in the humanities or life sciences.
Empirical-methodological perspective
Focus on single conspiracy theory topics
Most studies take one of the following two approaches: they either analyze conspiracy theories as a generic, abstract phenomenon, or they focus on specific, single conspiracy theory topics. In total, about one-third of all empirical studies in our sample (N = 144) followed the first approach (29.9%) and examined, for instance, generic conspiratorial beliefs and ideation (Essam et al., 2019A) or different online environments known to contain conspiratorial content such as BitChute (Trujillo et al., 2020A).
Most of the studies in our sample took the second approach and analyzed individual conspiracy theories (70.1%; see Figure 4). They interrogated health- and science-related conspiracy theory topics linked to the COVID-19 pandemic (16.7%), vaccination in general (13.9%), human papillomavirus (HPV; 5.6%), the Zika virus (4.2%), measles, mumps, and rubella (MMR; 2.8%), climate change (2.1%), or flat earth (2.1%). Others addressed more overarching polarizing topics centered around chemtrails (4.2%) or anti-Semitic narratives (2.1%). Some analyzed conspiracy theories related to events such as the 9/11 attacks (4.2%), the moon landing (1.4%), Pizzagate (1.4%), or the Sandy Hook shooting (1.4%). Cross-topic designs that allow for comparisons between different conspiracy theories were the minority, accounting for only 4.2% of all articles.

Analyzed conspiracy theory topics.
Focus on “mainstream” social media platforms
In terms of analyzed online environments, the large majority of analyses are single platform studies (81.2%) focusing mostly on social media platforms (70.1%; see Figure 5). The most frequently analyzed platforms are Facebook (23.6%), Twitter (20.1%), and YouTube (11.8%). In contrast, Reddit (6.2%), Instagram (4.9%), 4chan (2.1%), or Weibo (2.1%) were the minority. Furthermore, scholars empirically interrogated online news media (16%), followed by blogs and personal websites (6.2%), instant messengers (2.8%), search engines (2.1%), or discussion forums (2.1%). Only a minority of publications studied conspiracy theories in the context of fact-checking sites (1.4%) and news aggregators (1.4%).

Analyzed online environments.
Interest in conspiracy theories on online platforms has heightened from 2018 onward, in line with the general growth of research on conspiracy theories online. Platforms which are less regulated, such as Gab, 8kun, or 4chan, have only recently become an object of empirical analyses (e.g., Bagavathi et al., 2019A; Zannettou et al., 2018A).
Focus on “Western” countries and English-language communication
Another bias in the research field emerges in terms of the countries studied (see Table 1): a predominant focus on “Western” countries, that is, Europe with 23.6% of all empirical analyses, followed by North America with 15.3% and Oceania with 2.1%. Within these regions, however, research is diverse, with studies covering Italy (e.g. Mocanu et al., 2015A), the United Kingdom (e.g. Freeman et al., 2020A), Romania (e.g. Cmeciu and Coman, 2020A), Denmark (e.g. Stæhr, 2014A), Russia (e.g. Poberezhskaya, 2018A), the Netherlands (e.g. Lutkenhaus et al., 2019A), or Norway (e.g. Fangen and Holter, 2020A), among others. In addition, scholars have analyzed Asian regions (7.6%), such as China (e.g. Yang et al., 2014A), Bangladesh (e.g. Barua et al., 2020A), Japan (e.g. Okuhara et al., 2018A), Malaysia (e.g. Wong et al., 2020A), and Taiwan (e.g. Nefes, 2014A). Studies on Eastern European countries such as Bulgaria (e.g. Slavtcheva-Petkova, 2016A), the Czech Republic (e.g. Štětka et al., 2021A), Poland (e.g. Żuk and Żuk, 2020A), or the Ukraine (e.g. Zakharchenko et al., 2019A) are the minority, as are analyses on African (e.g. Essam et al., 2019A) or South American countries such as Chile (e.g. Halpern et al., 2019A). Only a few studies employed cross-country designs and analyzed more than one nation (4.2%).
Overview of countries and languages analyzed.
This “Western” focus is also present in those empirical analyses which focus on a specific language rather than a certain country (41.7% of all publications): In total, 33.3% of all empirical analyses focus on English-language communication, 1.4% on German, and 2.1% on multiple languages.
Focus on text-based content and exploratory approaches
Research on conspiracy theories online is diverse in its analytical and methodological approaches (see Table 2). In terms of applied research designs, half of all coded studies are case studies focusing on one conspiracy theory in one online environment within one national context. However, 12.5% of all empirical studies in our sample were case studies analyzing temporal developments by applying a longitudinal design. A total of 21.5% articles compared different conspiracy theory topics and/or online environments and/or countries in cross-sectional studies, while 4.9% combined, for instance, different online media without explicitly comparing them with each other.
Overview of analytical and methodological approaches.
Looking at the modality of data examined, a clear bias toward text-based content appears, which is analyzed in 78.5% of all coded articles. Other than these communication-centered studies, some publications focus on individuals (19.4%) as they explore the relationship between conspiratorial beliefs and digital media. Audiovisual and visual contents are less frequently studied, with only 8.3% and 4.9%, respectively.
In terms of analytical approaches, most articles used quantitative methods (67.4%) and an inductive approach (78.5%). By contrast, only 7.6% combined inductive and deductive approaches or qualitative and quantitative methods (13.2%).
Although the field of research is characterized by a variety of methods, manual content analysis is the most frequent (61.1%), followed by automated content (28.5%) and network analysis (19.4%). Research on individuals’ beliefs in conspiracy theories mostly relies on surveys (13.2%), interviews (3.5%), and survey experiments (2.8%). Simulation (2.1%) or ethnographical studies (1.4%) were only a small minority. At 28.5%, almost one-third of all empirical investigations leveraged mixed methods.
Research objects
With regard to research objects, six thematic categories emerged in a qualitative reading and synthesis of all empirical studies of our sample (
Representation
The first and by far largest category includes empirical studies examining how conspiratorial content is represented in digital media (
Production
The second thematic category captures empirical studies exploring different aspects related to the production of conspiratorial content online (
Dissemination
Another category of studies analyzes the dissemination and spread of conspiracy theories in online environments (
Debunking
Studies in the fourth category develop and evaluate debunking strategies (
Consumption
Only few studies in our sample (
Predictors and consequences of conspiratorial beliefs
While the majority of the above-mentioned categories ask how conspiracy theories are communicated online, the last category of research objects investigates the corresponding effects. The respective, scholars attempt to understand how digital media use and endorsement of conspiratorial content affect people’s willingness to believe or support such narratives (
The way ahead: Directions for future research
Digital technologies have catalyzed the dissemination of and communication about conspiracy theories. Not only did they amplify their visibility; they also led to an increase in research on conspiracy theorizing online. By providing the first comprehensive literature review of research on conspiracy theories in digital environments across disciplinary fields, we investigated the evolution of the field (
Our review showed that research on conspiracy theorizing online grew considerably, especially over the last 2 years, in a multitude of disciplines ranging from the arts and humanities to the life sciences, social sciences, and information science. We also found that researchers frequently publish outside of their home discipline in either mono- or multidisciplinary journals and work in interdisciplinary teams—most of these cooperations, however, remain within the same broader research tradition. Looking at the conceptual level of conspiracy theory research, our results show that the majority of studies lack a definition of conspiracy theories and fail to clarify the conceptual boundaries between conspiratorial narratives and other forms of deceptive content. However, those that did offer a definition shared a basic understanding of the phenomenon and its fundamental conceptual elements. Finally, our analysis highlights that the field suffers from empirical biases in four respects: it focuses strongly on single “mainstream” social media platforms, “Western” countries, English-language communication, and single conspiracy theory topics. By contrast, the field employs a variety of methodological approaches and investigates a host of research objects, such as the representation, dissemination, or debunking of conspiracy theories.
Based on these findings, the following sections provide conceptual and empirical building blocks that could help to remedy the identified shortcomings of current research and to set up new lines of research.
Clarifying the conceptual core and boundaries of conspiracy theories
To develop a better understanding of how conspiracy theories content—compared to other forms of deceptive information—operate in online environments, it is important to clarify their
Acknowledging reconfigurations of the platform ecosystem
Apart from conceptual shortcomings, our literature review indicates that research is dominated by a handful of “mainstream” social media platforms. While the respective scholarship has considerably enhanced our understanding of the characteristics and impacts of communicating conspiracy theories on specific platforms, future studies should move beyond single platform studies and focus more on the connectivity and dynamics of the wider platform ecology. This will generate more fruitful insights into how the convergence of new media technologies shapes the communication of conspiracy theories and how to improve related counterstrategies.Essentially, both the dissemination and regulation of conspiracy theories online should be perceived and analyzed as
Acknowledging national, cultural, and socio-political contexts
Another shortcoming of prior research concerns the predominant focus on single, often “Western” countries and English-language communication, which makes it difficult to detect the nuances in national, cultural, and socio-political differences in the characteristics and impacts of conspiracy theories. Gray (2008: 167) correctly pointed out that there is “no single theory of conspiracism that simply and neatly can explain conspiracism, much less one that can be taken from the Western experience.” To take the particularities of the local political, economic, and cultural climate into consideration, scholars need to provide more
In addition, we found a predominant focus on single conspiracy theory topics, which is problematic as previous studies suggests that conspiracy beliefs tend to “stick together” (Douglas et al., 2019: 7); thus, people who believe in one conspiracy theory are likely to also turn to others (van Prooijen, 2018). Moreover, research has shown that many online communities do not only evolve around one specific conspiracy topic, but often disseminate different conspiratorial narratives simultaneously (Mahl et al., 2021). To understand how conspiracy theories are aligned, and how national, cultural, and socio-political factors help to explain alignments between conspiracy theories,
Overall, this review has demonstrated that there is a trove of research on the interplay between conspiracy theorizing and digital media. However, it has also highlighted that further work is required—both on the conceptual and empirical level and with the help of interdisciplinary cooperation. We believe that our outlined suggestions offer valuable pathways to achieve these goals.
Supplemental Material
sj-pdf-1-nms-10.1177_14614448221075759 – Supplemental material for Conspiracy theories in online environments: An interdisciplinary literature review and agenda for future research
Supplemental material, sj-pdf-1-nms-10.1177_14614448221075759 for Conspiracy theories in online environments: An interdisciplinary literature review and agenda for future research by Daniela Mahl, Mike S. Schäfer and Jing Zeng in New Media & Society
Footnotes
Acknowledgements
The authors thank the two anonymous reviewers whose remarks substantially improved this article, as well as and Salome Bosshard and Lukas Tribelhorn for their assistance throughout the coding process.
Author agreement
All authors have agreed to this submission. We confirm that the article is not currently being considered for publication by any other print or electronic journal.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work is part of the research project “Science-related conspiracy theories online: Mapping their characteristics, prevalence, and distribution internationally and developing contextualized counter-strategies,” funded by the Swiss National Science Foundation (SNSF; Grant No. IZBRZ1_186296).
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