Results: 35 articles were included in the review, 30 of them were quantitative studies, two studies were mixed and three were qualitative studies.
Niðurstöður: 35 greinar voru með í yfirlitinu, 30 af þeim voru megindlegar rannsóknir, tvær rannsóknir voru með blandaðri aðferð og þrjár voru eigindlegar rannsóknir.