01 · The Question
How Broad Can a Scoping Review Be Before It Stops Being Informative?
Scoping reviews are supposed to be broad. That is part of their usefulness. They can map concepts, research approaches, evidence characteristics, knowledge gaps, and the extent of literature in areas where a narrowly specified systematic-review question may be premature.
But “broad” does not mean “almost anything related to the topic.” A question such as “What does the literature say about artificial intelligence in education?” may sound appropriate for a scoping review precisely because it is expansive. Once operationalized, however, it could encompass every educational level, country, AI technology, stakeholder, purpose, outcome, study design, and several decades of literature.
The methodological problem is therefore not breadth itself. It is whether the boundaries still allow you to produce a coherent and useful map of the evidence.
02 · The Short Answer
A Scoping Review Can Be Broad Without Being Boundless
In Brief
A scoping review is too broad when its question and eligibility criteria encompass so many substantially different populations, concepts, contexts, or evidence types that the review can no longer search, classify, map, and interpret the literature coherently enough to answer its stated purpose.
There is no universal maximum number of studies, populations, databases, or concepts that defines “too broad.” The appropriate scope depends on the review objective, the structure and volume of the evidence base, available resources, and what the resulting evidence map is intended to show.
03 · What You Need to Know
Breadth Is Useful Only When the Review Still Has a Definable Purpose
Scoping reviews normally ask broader questions than systematic reviews
JBI guidance describes scoping-review questions as generally broader than the questions used in more focused systematic reviews. This difference reflects their purposes. A systematic review might ask whether a particular intervention affects a defined outcome in a specified population. A scoping review may instead examine what kinds of evidence exist, how a concept has been studied, which methods have been used, or where apparent gaps remain.
That distinction is central when deciding between a systematic review and a scoping review . You should not narrow a scoping review merely because it does not resemble a tightly specified effectiveness review.
The question is whether its breadth serves the objective.
Use Population, Concept, and Context to expose hidden breadth
JBI recommends the Population, Concept, and Context framework, commonly abbreviated PCC, for developing scoping-review questions and eligibility criteria. Not every review necessarily requires all three elements to be restrictive, but explicitly considering them makes the boundaries visible.
PCC element
Useful question
Possible source of excessive breadth
Population
Whose evidence is relevant?
Including fundamentally different populations without a reason to map them together
Concept
What phenomenon, practice, intervention, characteristic, or idea is being mapped?
Using an umbrella concept that contains many poorly related phenomena
Context
In which settings, sectors, locations, or circumstances is the evidence relevant?
Including every possible setting when contextual differences make the literature difficult to interpret collectively
A broad population may be perfectly reasonable when the concept is tightly defined. A broad context may also be useful when comparing how the same phenomenon appears across settings. Problems arise when several dimensions are opened simultaneously without a clear analytical purpose.
The first warning sign is an unclear review question
JBI emphasizes that the review question provides the foundation for eligibility criteria, searching, screening, extraction, analysis, presentation, and findings. If the question itself is unclear, the review is likely to lack coherence.
Consider the difference between “What research exists on digital technology in higher education?” and “How have generative AI tools been used to support formative assessment in higher education?” Both can potentially support scoping reviews, but they imply dramatically different evidence spaces.
The first question might still be legitimate if the purpose is to map a deliberately enormous domain and the team has a defensible classification framework. If the researchers cannot explain what will be mapped once the literature is found, however, breadth is masking an unresolved research objective.
Excessive breadth often appears when you try to write the eligibility criteria
A useful practical test is to translate the question into explicit inclusion and exclusion criteria. JBI recommends clear alignment among the objective, question, and PCC-based eligibility criteria.
If almost every decision ends with “include it because it is somehow related,” the scope may be underdefined. Conversely, adding arbitrary restrictions merely to reduce the number of records can distort the purpose of the review.
Restrictions should therefore have conceptual or practical justification. Limiting the population to university students because the question concerns higher education is defensible. Limiting studies to countries beginning with certain letters because screening produced 20,000 records would be efficient in a rather unfortunate methodological sense.
Search results can reveal that the conceptual scope is unmanageable
A preliminary search is useful before finalizing a scoping-review protocol. A very large number of results does not automatically mean the question is too broad. Database searches commonly retrieve many irrelevant records, and some legitimate scoping reviews cover large evidence bases.
Instead, inspect what the search retrieves. If relevant records represent numerous unrelated meanings of the central concept, radically different populations, incompatible contexts, or evidence that cannot be organized around the review objective, the conceptual boundaries may need refinement.
The problem is therefore not simply “too many papers.” It is too many papers that cannot be meaningfully mapped together for the question being asked.
A large evidence base and an overbroad question are not the same problem
Large review
The evidence base is extensive, but the studies can still be classified and mapped coherently against a clear objective.
Overbroad review
The boundaries combine evidence so disparate that the resulting map becomes difficult to interpret or use, regardless of the exact number of included records.
This distinction matters because narrowing a question solely to reduce workload can remove evidence that is essential to its purpose. Feasibility matters, but it should be considered alongside conceptual coherence and intended use.
Ask what the final evidence map will actually contain
Before screening thousands of records, imagine the results section. What will you chart? What categories will organize the evidence? What patterns will answer the question?
If the anticipated result is essentially “many different things have been studied in many different ways,” the review may not yet have a sufficiently informative organizing question. A scoping review can legitimately reveal heterogeneity, but merely documenting that a vast field is heterogeneous rarely justifies mapping the entire field.
JBI notes that some scoping reviews benefit from subquestions addressing particular attributes of the population, concept, or context. Subquestions can help operationalize a broad primary question and clarify how the evidence will be mapped.
Broad scope becomes particularly problematic when the concept itself is unstable
Some topics use terminology inconsistently. Artificial intelligence, digital learning, well-being, engagement, sustainability, and similar umbrella concepts can refer to substantially different phenomena across disciplines and periods.
A scoping review can be useful precisely because terminology is unsettled. But researchers still need an operational understanding of what counts as evidence about the concept. Otherwise, inclusion decisions become dependent on intuition rather than reproducible criteria.
Watch Out
Do not solve conceptual ambiguity simply by searching one preferred term. A manageable search is not necessarily a valid search. Clarify what the concept means for your review, identify relevant terminology, and then determine whether the resulting scope remains feasible.
Sometimes the solution is several related reviews rather than one enormous review
If preliminary mapping reveals several distinct questions hiding inside one review, separating them may produce more useful syntheses. You might divide the evidence by population, intervention family, setting, purpose, or another theoretically meaningful distinction.
This should not be done mechanically. Fragmenting a question too aggressively can remove the broad perspective that justified a scoping review in the first place. The goal is not the narrowest possible question. It is the broadest question that can still produce a coherent answer to the stated objective.
04 · A Practical Example
From “AI in Education” to a Scopable Question
Hypothetical Example
Mapping generative AI in assessment
A research team initially proposes: “What is known about artificial intelligence in education?” Their preliminary search retrieves literature on intelligent tutoring systems, automated grading, learning analytics, predictive models, generative AI, administrative systems, academic integrity, special education, teacher development, and numerous other applications across schools, universities, vocational education, and informal learning.
Original scope
Population includes almost everyone involved in education; the concept includes almost every form of AI; the context includes virtually every educational setting.
Purpose check
The researchers realize that their actual interest is how generative AI is being incorporated into assessment practices in higher education.
Refined scope
They define the population and context around higher education and operationalize the concept around uses of generative AI associated with assessment.
Result
The review remains broad enough to map different assessment practices, disciplines, stakeholders, study designs, and reported uses, but those dimensions now contribute to one interpretable evidence map.
The refinement is not better merely because fewer papers will be screened. It is better because every included source can now contribute to a recognizable analytical purpose.
06 · What This Means for You
Find the Broadest Scope That Still Produces a Coherent Map
Do not begin by asking how many papers you are willing to screen. Begin by specifying what you want to know when the review is finished. Then work backward through the population, concept, context, eligibility criteria, search strategy, and data you intend to chart.
A simple decision framework
If the broad question has a clear mapping objective and defensible classification structure
Breadth may be appropriate even if the evidence base is large.
If several unrelated concepts are being included mainly because they share an umbrella label
Clarify the central concept or separate distinct questions.
If population or context differences are central to what you want to map
Keep them broad enough to examine that variation rather than narrowing them for convenience.
If you cannot specify how included evidence will be charted and organized
Refine the objective and question before conducting the full review.
If your real objective is to determine an intervention's effect or answer another focused synthesis question
Consider whether a systematic review rather than a scoping review better fits the purpose.
A protocol is particularly valuable here because it forces the intended boundaries to become explicit before the volume of literature starts influencing decisions. Consider what your review protocol needs to establish and whether preregistering the scoping review is appropriate.
Most importantly, preserve the reason you selected a scoping review. If narrowing the question eventually produces a tightly specified question requiring critical appraisal and synthesis to determine an effect, association, experience, or other defined answer, you may have crossed into a different review design rather than simply improved your scoping review.
07 · A Quick Checklist
Test Whether Your Scoping Review Has Useful Boundaries
Before finalizing the scope, check:
State exactly what the completed review is intended to map, describe, characterize, or identify.
Define the relevant Population, Concept, and Context elements and justify deliberately broad dimensions.
Translate the question into explicit inclusion and exclusion criteria before full screening begins.
Run preliminary searches and inspect the nature of the retrieved literature, not merely the number of results.
Determine whether relevant studies can be classified meaningfully against the review objective.
Identify the data-charting categories you expect to use and what each will contribute to answering the question.
Check whether one enormous question actually contains several conceptually distinct review questions.
Avoid restrictions introduced solely to make an inconvenient workload disappear unless they are also conceptually defensible.
Verify current scoping-review methodology against authoritative guidance such as the JBI Manual for Evidence Synthesis.
11 · Cite this Guide
How to Cite This Guide
This guide is intended to be read, shared, and used in research, teaching, and academic work. If you draw on its ideas, explanations, or other content, please acknowledge the source by citing the guide. Doing so gives appropriate credit and helps your readers locate the original resource.
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