Figure 3. Yields from searches, abstract review, and article review (Text description)

This chart describes the literature search process for this systematic review. A series of branching rectangular boxes connected by arrows illustrates the steps whereby articles were included or excluded from consideration.

The large rectangular box at the top of the chart is labeled "Abstracts identified from searches and additional sources^a for key questions 1-3 = 1316." The superscript "a" leads to a footnote that reads: "Abstracts were identified from reference lists, experts, and so forth."

An arrow proceeds downward from this first rectangle and forks immediately, pointing to 2 smaller rectangles. A legend at the left of this pair of rectangles, in the second tier, reads "Abstracts reviewed." The left-hand rectangle reads "Key questions 1 and 2^b = 1192." The superscript "b" leads to a footnote that reads: "Some studies overlap between key questions." The right-hand rectangle reads "Key question 3 = 124."

An arrow points straight downward from the second-tier left-hand rectangle to another rectangle labeled "Key questions 1 and 2 = 226. Similarly, an arrow points downward from the second-tier right-hand rectangle to another rectangle labeled "Key question 3 = 26. The legend at the left of the pair of rectangles in this third tier reads "Articles reviewed."

A pair of arrows forks diagonally downward to the left and right from the third-tier left-hand rectangle, to a pair of rectangles labeled respectively "Key question 1 = 2" and " Key question 2 = 7." A single arrow points straight downward from the third-tier right-hand rectangle, to a single rectangle labeled "Key question 3 = 11." The legend at the left of this fourth tier of 3 rectangles reads "Articles included."

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