What is snowballing in a literature review?

Snowballing is a literature search method that starts from papers you have already included and follows their references (backward snowballing) and the papers that cite them (forward snowballing). New relevant papers are screened with the same criteria and snowballed in turn, until no new studies appear. It catches studies that database searches miss.

Report snowballed studies separately in your PRISMA flow diagram.

Forward snowballing needs a citation index, such as Semantic Scholar, OpenAlex or Crossref.