What PICO means
PICO is a framework for clinical questions about interventions:
- P: Population. Who are the patients or participants?
- I: Intervention. What's being done to them?
- C: Comparator. Compared with what?
- O: Outcome. What are you measuring, and when?
It's the standard way to frame an intervention review in clinical research. It also shapes almost everything after it: your eligibility criteria, your search terms and the "eligibility criteria" item in your PRISMA write-up.
A worked example
Topic: mindfulness for postpartum depression.
- P: Adults within 12 months after giving birth with depressive symptoms.
- I: Mindfulness-based interventions (for example, MBCT), any delivery mode.
- C: Usual care, waitlist or an active control.
- O: Change in depressive symptoms on a validated scale at end of treatment.
PICO question: In adults within 12 months postpartum with depressive symptoms, do mindfulness-based interventions, compared with usual care, waitlist or active controls, reduce depressive symptoms at end of treatment?
Now you know what to search for, what to exclude and what to extract. Notice what the question leaves out. It doesn't say "does mindfulness work?" It names who, against what and measured how. That's what makes it screenable. Two people reading the same abstract should reach the same yes or no.
How to write a PICO question in five steps
- Write the messy version. One sentence, in your own words. Don't polish it.
- Pull out the four parts. Underline the population, the intervention, the comparison and the outcome. If one is missing, that's your gap.
- Make each part specific enough to screen against. "Older adults" is vague. "Adults aged 65 and over living in the community" isn't.
- Pick one primary outcome. You can list secondary outcomes, but one has to lead. It keeps the review honest and the write-up short.
- Read it to someone outside your field. If they can't tell who, what and compared with what, rewrite it.
When PICO doesn't fit
PICO suits intervention questions. Other question types often use variants:
- PICOS adds S: Study design (for example, RCTs only).
- PICOT adds T: Time frame.
- PECO swaps the intervention for an Exposure. Use it for questions like "Does air pollution exposure raise asthma risk?"
Qualitative and prevalence questions often use other frameworks. Ask your supervisor which your programme prefers, and say which you used in your methods.
Common PICO mistakes
- An outcome that's really a topic. "Wellbeing" isn't measurable. "Score on a validated anxiety scale" is.
- A population that drifts. If your P says adults, don't quietly include adolescent studies at screening.
- Changing the question after you see results. Register your protocol and stick to it, or report the change and why.
From PICO to search terms
Each PICO part becomes a block of search terms. Within a block, join synonyms with OR. Between blocks, join with AND. Comparators and outcomes are often left out of the search itself and applied at screening instead, so you don't miss studies that report them badly in the abstract.
For where to run that search, see how to search open-access literature.
A PICO question builder
Systematic Review has a PICO question builder (/app/pico). You fill in the Population, Intervention, Comparator and Outcome yourself and save the question. It doesn't write a PICO for you. You write the question and stay in charge of it. Included in student plans. Join the waitlist to hear when checkout opens.
Don't paste identifiable patient details into any online tool.
If you use AI to help frame your question, note it in your disclosure. Our guide to disclosing AI use covers what to write.
FAQ
What is a PICO question?
A clinical question split into Population, Intervention, Comparator and Outcome, so it can be searched and screened consistently.
Is a PICO framework generator allowed for my dissertation?
It depends on your course's AI rules. Many UK courses allow AI help with planning if you disclose it. Check your handbook, then record what you used.
Do I need a comparator?
For an intervention review, usually yes, even if it's "usual care" or "no intervention". If there's truly no comparator, say why.
PICO or PICOS?
PICOS adds study design. Use it if you're limiting to certain designs, such as RCTs.