What is PICO?

PICO is a framework for writing a focused research question, especially in health research: Population (who), Intervention (what is done), Comparison (compared with what) and Outcome (what is measured). Each element becomes a block of search terms, and the blocks set the inclusion criteria of a systematic review.

Variants add Time or Study design (PICOT, PICOS). Outside health, similar frames such as SPIDER or a plain scope statement do the same job.

A clear PICO makes screening faster, because each record is checked against the same four questions.