Most medical systematic reviews need 12–24 months from idea to publication, with scope, staffing, and methods driving the timeline.
Planning an evidence synthesis is a project, not a task. The calendar depends on the research question, the volume of studies, and how your team moves through screening, extraction, analysis, and write-up. Below, you’ll see the usual range, the stages that consume time, and proven ways to keep momentum without cutting corners.
The Typical Timeline At A Glance
This overview shows where months tend to land. It reflects common workflows used in health research teams, including dual screening, risk-of-bias assessment, and clear reporting.
| Stage | Typical Time Range |
|---|---|
| Scope & protocol (question, eligibility, search plan) | 4–8 weeks |
| Extensive searching & deduplication | 3–6 weeks |
| Title/abstract screening (dual reviews) | 4–10 weeks |
| Full-text screening (dual reviews) | 4–10 weeks |
| Data extraction & risk-of-bias | 6–12 weeks |
| Meta-analysis & sensitivity checks | 3–8 weeks |
| Write-up & PRISMA flow | 4–8 weeks |
| Peer review & revisions | 6–16 weeks |
How Long A Medical Evidence Review Usually Takes (And Why)
Across health sciences libraries and methods papers, one year to two years is common. Teams with a narrow question, a modest pool of eligible trials, and smooth collaboration often land near the shorter end. Broad questions, complex comparators, or multiple outcomes add months.
What Recent Studies Report
Methods research has tried to measure the real effort. A multi-site analysis estimated about 67 weeks from project start through publication, with wide spread by topic and team size. A registry study tracking protocol registration to the final article found a median near two years, with a tail past five years for a subset. Recent audits in specific cohorts reported medians around 11–16 months from initiation to publication. Taken together, these snapshots explain why many planners budget 12–24 months for a full cycle.
Why The Clock Stretches
Four drivers show up again and again: the number of records retrieved, the availability of trained screeners, the complexity of data items, and the presence of meta-analysis. Dual screening and duplicate extraction raise quality but also extend the schedule. Journal peer review adds more time at the end, especially when major edits are needed.
Stage-By-Stage: What To Expect
Scope And Protocol
Clear eligibility and a registered protocol prevent rework later. Teams set PICO elements, outcomes, subgroups, and the search plan. A short, precise scope shortens screening and extraction. A broad scope does the opposite.
Searching And Record Management
Experienced search specialists map terms and subject headings across databases, then manage deduplication from multiple sources. Search quality drives everything downstream. Weak search strings look fast at first, then cost time when gaps are spotted during peer review.
Screening In Two Passes
Most groups run title/abstract screening first with at least two independent reviewers, then move shortlisted studies to full-text screening. Calibration at the start prevents disagreements later. Software helps with workload distribution, but trained judgment still anchors each include/exclude decision.
Data Extraction And Risk Of Bias
Extraction templates should be piloted on a handful of papers before full rollout. That trial run shakes out unclear fields and prevents later rewrites. Bias tools differ by study design; matching the tool to the design avoids wasted effort.
Analysis And Synthesis
Not every project ends with a pooled estimate. Some questions call for structured narrative synthesis. When meta-analysis is appropriate, you’ll budget extra time for model checks, subgroup analyses, and grading the certainty of evidence.
Writing And Reporting
Clarity at this stage saves cycles with editors. Use a structured abstract, describe the search window, present the flow diagram, and link methods and results tightly. Tables and clean forest plots help readers verify the work fast.
Trusted Standards That Shape Timelines
Transparent reporting is part of the work. The PRISMA 2020 checklist sets a clear template for what to report in a health intervention review, from title through funding. Building your outline around that list prevents last-minute hunts for missing details.
Updating And Keeping Evidence Current
Evidence shifts. Many groups check currency on a cycle and update when new trials change the picture. Historical analyses suggest a median of about three years between updates for reviews that include a meta-analysis. For high-velocity topics, living models keep searches running and add new studies as they appear.
What Shortens Or Lengthens The Work
Below are practical levers that push timelines up or down. Use them to plan resources and set expectations with collaborators.
| Factor | Effect On Time | Notes |
|---|---|---|
| Scope width | Wider scope = more months | Narrow, focused PICO trims screening. |
| Team size | More screeners = faster | Quality requires dual work; more pairs help. |
| Search strategy | Better search = smoother | Strong strings reduce missed studies and rework. |
| Study designs | Mixed designs = slower | Different bias tools and data fields add steps. |
| Meta-analysis | Adds weeks | Model checks and heterogeneity testing take time. |
| Data availability | Low reporting = slower | Contacting authors can add long waits. |
| Peer review round | Major revisions = months | Clear methods and visuals reduce cycles. |
Planning Scenarios You Can Use
Lean Question, Small Literature
A single comparator, one or two primary outcomes, and a handful of eligible trials. With two or three trained reviewers and a librarian, six to ten months is realistic from protocol to a submitted manuscript. Add journal review time on top.
Moderate Breadth, Mixed Designs
Multiple comparators or mixed RCTs and observational studies. Expect a year or more. Calibration time, separate bias tools, and more nuanced synthesis add weeks, not days.
Broad Scope Or Network Meta-analysis
Many interventions, multiple outcomes, and complex models. Expect the long end of the range. This is where two years from idea to publication becomes common, especially when field experts request extra analyses during peer review.
Evidence On Workload And Staffing
One methods paper tallied hours across tasks and found wide variation tied to the number of included studies and the size of the team. Pairing reviewers and involving an information specialist cut errors and rework. That staffing model adds cost but pays back by avoiding restarts at the analysis stage.
What “Living” Means For Timing
A living model keeps the review online and refreshed as new trials appear. Teams run frequent searches, triage hits, and append updates in small batches. It spreads the work out and keeps the findings current, which matters on topics where new data keeps arriving.
Common Bottlenecks And How To Unblock Them
Slow Full-Text Retrieval
Library access and interlibrary loan can stall screening. Batch requests early, and track any papers that need follow-up.
Unclear Eligibility
Ambiguity breeds conflict. Pilot screening on a small set and refine rules with examples so calls stay consistent.
Messy Extraction Sheets
Too many fields slow teams down. Start lean, expand only when an item shapes a decision or analysis.
Late Statistical Questions
Bring a methodologist in while drafting the protocol. Catching modeling choices late triggers redo cycles.
Submission, Peer Review, And Publication
Once the manuscript is ready, journal timelines vary. Some decisions arrive in six to eight weeks, others take longer. Plan for at least one round of revisions that may include additional analyses or clarifications. The clock stops only on acceptance.
Real-World Benchmarks From Recognized Sources
Public health and methods groups publish estimates. Health agency guides cite an average near eighteen months for a full cycle. An institutional registry study reported two years from protocol to final article in a large sample. Other cohorts have reported medians around one year to publication. Together, these datapoints frame a realistic window.
For reporting, lean on the PRISMA 2020 checklist. For workload expectations, see the BMJ Open time-and-workers study that documents the 67-week figure and the tasks that consume it. Linking your plan to those references strengthens grant timelines and keeps teams aligned.