Articles included in the final analysis were reviewed for quality using multiple criteria,
because of the difficulty in comparing and contrasting heterogeneous study
approaches. To capture the value of studies that ranged from descriptive to controlled
trials, we started with a descriptive discussion of their strengths and weaknesses. We
then applied Downs and Black’s (1998) criteria for assessing methodological quality,
using the first 26 items in the scoring system, which had a possible total score of 27.