“…The major themes that emerged from the studies were the positive effects of and reasons for substance use from homeless youth's perspective [3,22,24,27], psychosocial variables of homeless youth and SU, properties of social networks and effects on SU [5,25,[28][29][30], the heterogeneity of homeless youth [18,20,26,31], and the lack of knowledge and effective interventions for this highly vulnerable subgroup [2,16,20,23]. The disaffiliation of emerging adults from social institutions and mainstream society is also a concern [1,21,31] while there are few effective interventions or policies to address this growing issue [21,32].…”