Table 2.

Descriptive characteristics of subcategories.

Subcategory	Number of articles reviewed	Mean age of participants (years)	Study design not available
Age	10	13.92	All Available
Gender	16	15	Experimental
Pubertal status	3	12.2	Experimental
Genetic vulnerability	5	16.2	Longitudinal and Experimental
Personality	16	13.91	All Available
SU expectancies and motives	1	14.04	Cross-sectional Experimental
Peer Relationship characteristics	10	12.77	All Available
Parental factor	17	14.29	Experimental
School Context	3	14.8	Experimental
Neighborhood context	2	17	Experimental