Most full systematic reviews take 12–18 months from protocol to submission, with staged milestones and defined roles.
Planning and completing a full evidence review isn’t a weekend project. You move through a set of stages—question framing, protocol drafting, search design, screening, appraisal, synthesis, and write-up. Each stage has its own pace, dependencies, and handoffs. The timeline below shows what teams usually face, plus the factors that speed things up or slow them down.
Stage-By-Stage Timeline At A Glance
This overview sets expectations for a typical health or social-care review that follows established guidance such as the Cochrane Handbook and PRISMA reporting. It assumes a trained team, access to databases, and a focused question.
| Stage | Typical Duration | Core Outputs |
|---|---|---|
| Refine Question & Scope | 1–3 weeks | PICO/eligibility, draft outcomes, stakeholder aims |
| Protocol & Registration | 1–2 months | Registered protocol (e.g., PROSPERO), planned methods |
| Search Strategy Design | 2–4 weeks | Database list, peer-reviewed search strings, test runs |
| Comprehensive Searching | 1–3 months | Executed searches, deduplicated library, search log |
| Title/Abstract Screening | 3–6 weeks | Dual-screen decisions, PRISMA flow numbers |
| Full-Text Screening | 1–2 months | Final inclusion set, reasons for exclusion |
| Data Extraction | 1–2 months | Extraction sheets, contact log for missing data |
| Risk Of Bias Appraisal | 3–6 weeks | Tool-based judgments (e.g., RoB 2), inter-rater notes |
| Synthesis & Meta-analysis | 1–2 months | Effect models, heterogeneity checks, sensitivity runs |
| Drafting & PRISMA Reporting | 1–2 months | Structured manuscript, PRISMA checklist & flow diagram |
| Internal Review & Submission | 3–6 weeks | Author revisions, target journal submission |
Those ranges add up to about 12–18 months in many academic settings. Several library and methods groups echo that estimate, and many anchor expectations around the 18-month mark for a full review from idea to manuscript.
Time Needed For A Systematic Review Project
People often ask for a single number. A common answer is “about a year to a year and a half.” That range reflects what method groups report for a standard review with careful screening, risk-of-bias work, and PRISMA-style reporting. Some teams finish near the 12-month end when the question is narrow and the set of eligible studies is modest. Broader topics, mixed designs, or complex interventions tend to drift beyond 18 months.
What Drives The Clock
Four drivers shape the schedule: scope, search volume, team capacity, and methods choices. Scope sets eligibility rules. Search volume sets how many records you must screen. Team capacity sets throughput at each stage. Methods choices add or reduce steps. A meta-analysis with subgroup plans, GRADE certainty profiles, and sensitivity checks needs more time than a narrative synthesis of a small body of trials.
Scope And Question Shape Everything
Narrow inclusion rules trim the pile fast. Broad rules pull in many study types and settings. When outcomes or comparators vary a lot, you may split analyses or plan separate syntheses. Each branch adds extraction and appraisal time.
Search Strategy And Databases
Method guides encourage comprehensive, reproducible searches with peer review of strategies and full logs. Search design itself is quick; running and managing the results takes longer, especially with multiple databases and grey sources. PRISMA-S provides a clear checklist for documenting searches from strings to deduplication steps.
Screening Workflow
Dual screening at title/abstract and full-text stages adds quality and reduces missed studies. Tools with conflict resolution and calibration exercises improve agreement but add short setup time. A pilot of 100–200 records aligns decisions early and saves rework later.
Extraction, Bias Appraisal, And Synthesis
Extraction templates speed work when fields are standardized. Trials with multiple arms, cross-over designs, or cluster effects add calculation steps. Bias tools bring structure to judgments and feed straight into summary tables and GRADE profiles. Meta-analysis adds modeling choices and diagnostics such as heterogeneity and small-study signals.
Author Roles And Team Size
A lean team usually includes a content lead, a methods lead, and an information specialist. Many library guides advise at least three contributors to maintain dual screening and appraisal without bottlenecks. Larger teams move faster through screening, yet coordination overhead grows. Clear roles, a living task board, and weekly check-ins keep momentum.
Typical Timeline For A Full Evidence Synthesis
Here’s a practical way to pace the work across a year-plus. Treat the months as targets, not rigid deadlines. Real projects shift based on recruitment, holidays, or journal feedback.
Months 1–2: Protocol Locked
Finalize the question, populations, comparators, outcomes, and study designs. Register the protocol and decide on any subgroup or sensitivity plans. Lock outcomes before running full searches.
Months 3–5: Searching And De-Duplication
Run database searches, export to a reference manager or screening tool, and remove duplicates. Capture all logs and versions. Prepare grey-literature steps if needed.
Months 5–7: Dual Screening
Calibrate decisions on a pilot set, then divide records for parallel screening. Track conflicts for senior resolution and record exclusion reasons that map to PRISMA flow boxes.
Months 7–9: Extraction And Bias Judgments
Build or reuse extraction templates. Train on two or three studies to align coding. Record bias judgments with tool-specific rationales to support transparency later.
Months 9–11: Synthesis And Drafting
Run meta-analysis where studies align. Add narrative synthesis where pooling doesn’t fit. Create figures, summary tables, and certainty ratings that readers can scan fast.
Months 11–13: Internal Review And Submission
Cycle through co-author edits. Complete the checklist, flow diagram, and appendices. Select a target journal and align with house style before submitting.
Rapid Reviews And When They Fit
Time-boxed projects sometimes adopt streamlined methods—limited databases, single screener with verification, or narrower outcomes. These projects trade scope or redundancy for speed. They help policy teams meet near-term deadlines, but they are not a full substitute for exhaustive methods when the stakes demand depth.
Benchmarks From Recognized Guides
Several method hubs share practical time ranges and checklists that teams use every day. PRISMA 2020 lays out what to report, from search details to study selection. The Cochrane Handbook describes each stage from protocol to synthesis. Many university libraries post service pages that estimate 12–18 months for a complete project. Linking your workflow to these guides keeps the project traceable and saves time when reviewers ask for details.
Tools That Trim Weeks
Good tools don’t write the review; they remove friction. Screening platforms with bulk actions and conflict views clear large queues faster. Citation managers with solid deduplication cut noise before screening. Analysis packages that plug straight into extraction sheets spare tedious re-entry. A style guide and prebuilt tables keep the draft clean on the first pass.
Common Delays And How To Avoid Them
Scope creep: when eligibility rules expand midstream, the search grows and the clock extends. Freeze the protocol before running full searches.
Underpowered team: a single screener becomes a bottleneck as record counts rise. Aim for two screeners and a third for conflicts.
Late data gaps: missing variance data or unclear group sizes can stall synthesis. Contact authors early with a short, specific request.
Version chaos: methods text, search logs, and extraction sheets drift across folders. Use a shared workspace and name files with dates.
What A “Fast” Year Looks Like
Speed comes from clarity and cadence. A tight question with consistent comparators shrinks the eligible set. A trained trio keeps dual screening steady without waits. A weekly half-hour stand-up clears conflicts, assigns tasks, and keeps the log current. That setup lands near 12 months for many teams.
When Timelines Stretch Beyond 18 Months
Three patterns extend schedules. First, complex interventions with multiple components and outcomes lead to thicker data extraction and layered analyses. Second, mixed designs or cluster trials add adjustments and sensitivity checks. Third, stakeholder requests late in the game—new subgroups or extra outcomes—restart searches or extractions. Plan gates for scope changes to avoid resets.
Quality Signals That Save Time Later
Write decisions once and reuse them. Short rationale notes for inclusion, bias calls, and sensitivity choices feed straight into the manuscript. Keep the PRISMA flow up to date from day one. Save search strategies exactly as run, including dates, database platforms, and any filters. That traceability shortens peer-review rounds.
Second Reference Table: Time Drivers And Impact
| Driver | Impact On Time | Practical Move |
|---|---|---|
| Question Breadth | Broader scope increases records and heterogeneity | Split into sub-reviews or tighten outcomes |
| Team Size | Too few screeners slow dual review | Add a second screener and a tie-breaker |
| Search Sources | More databases add de-dup and management | Prioritize core databases; log grey sources |
| Study Designs | Cluster/crossover add analysis steps | Plan adjustments in protocol |
| Data Completeness | Missing stats stall pooling | Contact authors early with a template |
| Reporting Standards | Incomplete logs trigger revise-and-resubmit | Maintain PRISMA files as living documents |
Where To Anchor Your Methods
Two touchstones help readers and peer reviewers trust the work. First, align your reporting with the PRISMA 2020 statement. Second, match process steps to the Cochrane Handbook. Both links include concrete checklists and examples that map directly to day-to-day tasks. PRISMA-S extends this with clear guidance for documenting searches, strings, and deduplication artifacts.
A Straight Answer To The Timeline Question
Give yourself 12–18 months for a full, methods-driven review from protocol to submission. Plan the stages, staff dual screening and appraisal, and keep reporting assets current as you go. Tight scope, steady cadence, and early decisions are what bring projects in near the 12-month end; broader topics and complex designs move the finish closer to 18 months or beyond.