Table 3. The results of Cox proportional hazards model .

Time distance	Variable	Hazard Ratio	STD error	CI (95%)	p
1-12 months	First time substance abuse age	0.945	0.019	0.908,0.983	0.005
	History of taking any kind of medications for any reason	1.14	0.061	1.026,1.268	0.014
	The number of treatments	0.974	0.008	0.96 , 0.99	0.002
13-36 months	Other kinds of substance abuse	0.931	0.023	0.886,0.978	0.005
37-53 months	Employment status	0.94	0.025	0.891,0.992	0.026
	Other kinds of substance abuse	1.058	0.030	1.001,1.119	0.044