Factors affecting smoking behavior in included studies	Number of studies per factor	Number of studies reporting a positive strength of the factor significantly affecting smoking behavior
Smoker in the family	27 (55.1%)	8 (29.6%)
Lack of awareness of the consequences of smoking	16 (32.7%)	5 (31.3%)
Easy access to cigarettes	14 (28.6%)	4 (28.6%)
The lack of governmental laws to sell cigarettes to adolescents	3 (6.1%)	0 (0.0%)
Deaths of family members	9 (18.4%)	6 (66.7%)
Gender	23 (46.9%)	15 (65.2%)
Smoking friends	17 (34.7%)	13 (76.5%)
Dissatisfaction with family	11 (22.4%)	6 (54.5%)
Highly emotional environment	8 (16.3%)	3 (37.5%)
Divorce	5 (10.2%)	2 (40.0%)
Family disputes	12 (24.5%)	7 (58.3%)
History of school and family escape	3 (6.1%)	1 (33.3%)
Curiosity about smoking experience	9 (18.4%)	6 (66.7%)
Social problems	7 (14.3%)	2 (28.6%)
Low parental education level	10 (20.4%)	4 (40.0%)
Low family economic level	15 (30.6%)	2 (13.3%)