Understanding extremism in Scotland: evidence review

A report which reviews evidence on defining extremism and the extent and nature of extremism in Scotland.

2. Methodology

2.1. Search strategy

To conduct the review a search strategy was firstly developed, including search terms and tools.

Search terms

The search terms were derived from the research questions. A range of preliminary keyword searches were developed, which were tested and refined based on the results of initial searches. The final search terms are detailed in Table 1.

Table 1: Search terms

Research question 1: Defining extremism

  • Extremism + Definition
  • Extremism + Define
  • Extremism + Defining
  • Extremism + Understanding
  • Extremism + Meaning
  • What is extremism
  • What is extremism + Scotland

Research question 2: The prevalence of extremism

  • Extremism + Scotland / UK
  • Extremism + Amount + Scotland / UK
  • Extremism + Level + Scotland / UK
  • Extremism + Scope + Scotland / UK
  • Extremism + Extent + Scotland / UK
  • Extremism + Prevalence + Scotland / UK
  • Extremism + Scale + Scotland / UK
  • Extremism + Measure + Scotland / UK
  • Extremism + Amount
  • Extremism + Level
  • Extremism + Scope
  • Extremism + Extent
  • Extremism + Prevalence
  • Extremism + Scale
  • Extremism + Measure

Research question 3: The nature of extremism

  • Extremism + Nature + Scotland / UK
  • Extremism + Types + Scotland / UK
  • Extremism + Variants + Scotland / UK
  • Extremism + Threats + Scotland / UK
  • Extremism + Threat picture + Scotland / UK
  • Extremism + Threat landscape + Scotland / UK
  • Extremism + Nature
  • Extremism + Types
  • Extremism + Variants
  • Extremism + Threats
  • Extremism + Threat picture
  • Extremism + Threat landscape

Search tools

Three main search tools were used, to maximise the chances of capturing all relevant evidence.

Electronic databases

In the first instance, the search terms were entered into the online search engine KandE. KandE was developed by the Scottish Government Library Service and covers a range of academic and other research databases, which are detailed in Table 2.

Table 2: KandE Databases

Search engines

  • Academic Search Ultimate (asn)
  • AGRIS (edsagr)
  • Australian Research Data Commons (edsard)
  • BioOne Complete (edsbio)
  • Bloomsbury Collections (edsblc)
  • British Standards Online (edsbsi)
  • Business Source Index (bsx)
  • Cochrane Database of Systematic Reviews (edschh)
  • Credo Reference (edscrc)
  • Credo Reference: Academic Core (edscra)
  • Criminal Justice Abstracts with Full Text (i3h)
  • DigitalNZ (edsdnz)
  • Emerald Insight (edsemr)
  • ERIC (eric)
  • FT.com (edsfit)
  • GreenFILE (8gh)
  • Military & Government Collection (mth)
  • New Palgrave Dictionary of Economics Online (edsdeo)
  • Oxfam Policy & Practice (edsoxf)
  • Oxford Bibliographies (edsobb)
  • Oxford Dictionary of National Biography (edsodb)
  • Oxford Reference (edsoro)
  • Oxford's Who's Who & Who Was Who (edsoww)
  • Political Science Complete (poh)
  • Public Information Online (edspio)
  • RePEc (edsrep)
  • SAGE Knowledge (edsskl)
  • SAGE Research Methods (edsrem)
  • ScienceDirect (edselp)
  • Sociology Source Ultimate (sxi)


  • Directory of Open Access Journals (edsdoj)
  • JSTOR Journals (edsjsr)


  • Books at JSTOR (edsjbk)
  • eBook Collection (EBSCOhost) (nlebk)

Library services

  • Biodiversity Heritage Library (edsbhl)
  • British Library Document Supply Centre Inside Serials & Conference Proceedings (edsbl)
  • British Library EThOS (edsble)
  • Canadian Electronic Library (edscel)
  • E-LIS (Eprints in Library & Information Science) (edseli)
  • Library, Information Science & Technology Abstracts (lxh)


  • Archive of European Integration (edsupe)

The search terms were also entered into databases which focus specifically on social science, criminal justice and extremism and terrorism-related research, including:

  • Sociological Abstracts
  • Social Science Abstracts (SocialSciAbs)
  • Studies in Conflict & Terrorism
  • Terrorism and Political Violence
  • Perspectives on Terrorism
  • Journal for Deradicalisation
  • Security Journal
  • Critical Studies on Terrorism

Snowballing and hand searches

A snowballing method was also used, which involved reviewing the reference lists of identified studies in order to identify further potential sources. A series of broader keyword searches were then conducted using Google and Google Scholar, as a sweep of studies that may not have been found in the initial search.

Stakeholder assistance

Finally, stakeholders provided advice on research that had been carried out on this topic in Scotland. The stakeholders included academics and UK Government departments.

2.2. Coverage and inclusion and exclusion criteria

The review concentrated on evidence relating to the research questions, meaning that the focus was on studies seeking to define extremism and explore its extent and nature, particularly in Scotland. Studies that focused on other elements of extremism, such as its impact, risk and protective factors, and the prevention of extremism, were excluded.

To ensure the evidence was current and relevant, the initial time-period specified for the search was between 2012 and mid-2022 (when the review was carried out). However, due to a lack of Scotland-specific evidence identified in the initial search, the time-period was extended to between 2005 and mid-2022. Only evidence that was written or available in English was included. In relation to research questions two and three, Scotland-specific evidence was prioritised, as well as UK-wide studies which included evidence on Scotland. This was reflected in the search terms used to identify evidence for inclusion. However, where relevant to the research questions and available in English, evidence from other countries was also included.

The review focused predominantly on journal articles, books and book chapters, and reports from governments and independent/non-governmental organisations. Grey literature such as conference papers, published theses and other unpublished work was also included. Student papers, dissertations, opinion pieces and news articles were excluded.

Table 3 summarises the inclusion and exclusion criteria applied to the selection of the studies.

Table 3: Inclusion and exclusion criteria

In scope

Aim of study:

  • Research seeking to define extremism or review existing definitions
  • Research seeking to explore the prevalence, extent and nature of extremism, particularly in Scotland and the wider UK

Date: 2005-2022

Language: Written or available in English

Publication format:

  • Journal articles, books/book chapters, government and non-government reports
  • Grey literature such as conference papers and theses

Out of scope

Aim of study:

Research focusing on other elements of extremism, such its impact, risk and protective factors, and the prevention of extremism (including the impact and effectiveness of Prevent)

Date: Before 2005

Language: Not written or available in English

Publication format: Student papers, dissertations, opinion pieces and news articles

2.3. Search results

The initial search for evidence yielded over 3,000 results. The application of the above criteria led to a body of evidence consisting of 128 studies. Details of these studies, including bibliographic and methodological information, can be found in Appendix A.

The majority of the studies were published between 2006 and 2022. One study was included that was published prior to 2005 (Sotlar, 2004), due to the findings being highly relevant to the review. In addition, the report also covers the most recent data on referrals to Prevent in Scotland and England and Wales, which were published in 2023 (Home Office, 2023; Police Scotland, 2023).

Most studies presented evidence from the UK (76), including 27 which presented evidence on Scotland, followed by studies which presented evidence from more than one country (24) and studies from the USA (7).[1]

Other studies which provided relevant contextual information but which were not directly relevant to the research questions are included in the Reference list.

2.4. Quality assessment and limitations

The body of evidence was quality assessed, which involved reviewing the characteristics of the studies and their strengths and limitations. While the evidence identified was generally found to be high in quality, a key issue was the lack of empirically-grounded research. Many studies were theoretically-driven, with strong reliance on data gathered from secondary sources and literature review-based methods. While this was not particularly problematic for the first research question, which focused on exploring how extremism is defined in the literature, it presented challenges in relation to the second and third research questions, which were focused on gaining understanding of the prevalence and nature of extremism in Scotland. This criticism has been noted elsewhere; for example, Schuurman (2018) argues that the lack of primary research and empirical data is an enduring issue in the study of extremism and terrorism, and has hampered the development of new insights in this field.

Additionally, a distinct lack of evidence from Scotland was identified when carrying out the review, with the majority of purportedly UK-wide studies having been undertaken predominantly in England. This presented difficulties given that the focus of the review was on exploring extremism within Scotland, and meant that the conclusions that could be drawn about extremism in Scotland specifically were limited, as will be discussed later in the report.

It is also important to note wider limitations with this review; in particular, the application of a range of inclusion and exclusion criteria mean that while this report covers a range of literature on extremism, it should not be regarded as a comprehensive or definitive account of the evidence. Rather, it constitutes a collation of material relevant to the research questions which could be accessed using available channels. The review is further limited by inherent difficulties in assessing the scale of an issue that is by its nature often covert or hidden, and by the lack of a universally agreed definition of the term extremism, which makes it challenging to measure, as will be discussed in section 4.


Email: SVT@gov.scot

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