Table 6.

Group matching according to the number of subjects, age, gender, and education.

Group matching	Articles
One group only (15)	[143–155, 158, 166]
Number, age, gender, education (8)	[26, 37, 66, 81, 103, 115, 124, 176]
Number, age, gender (10)	[38–40, 86, 89, 90, 102, 118, 119, 173]
Number, age, education (7)	[77, 95, 98, 99, 111, 164, 165]
Age, gender, education (4)	[82, 128, 162, 168]
Number, age (18)	[42, 80, 94, 100, 108–110, 112, 120–122, 132, 134, 136–139, 172]
Number, gender (2)	[88, 142]
Number, education (3)	[58, 79, 167]
Age, gender (3)	[78, 84, 123]
Age, education (3)	[129, 169, 171]
Number (8)	[83, 87, 97, 107, 117, 135, 140, 163]
Age (12)	[41, 91, 92, 96, 113, 114, 125–127, 141, 175, 178]
Not paired or no information (19)	[85, 93, 101, 104–106, 116, 130, 131, 133, 156, 157, 159–161, 170, 174, 177, 179]