2.2. Methodological quality assessment
The quality of included studies was assessed by the adapted criteria for methodological quality assessment published elsewhere (Luppa et al., 2012). Each criterion was rated from 0 to 2 points (see Table 1). Studies scoring 75% or more of the maximum score (≥14 points) were rated as ‘high quality’, studies scoring between 50% and 75% (9–13 points) were considered ‘moderate quality’, and studies with lower than 50% (9 points) were considered ‘low quality’.