Table 2.

Results of the regression analysis for the duration of drug use

Characteristics		Coeff. †	95%CI ‡	p-value*
Recruitment site (ref.: centre no. 1)	centre no. 2	2.14	(-0.92, 5.21)	0.1703
	centre no. 3	-2.29	(-4.44, -0.13)	0.0376
	centre no. 4	1.35	(-1.05, 3.74)	0.2696
	centre no. 5	3.33	(1.36, 5.31)	0.0010
	centre no. 6	2.11	(-0.63, 4.86)	0.1315
	centre no. 7	1.17	(-1.92, 4.26)	0.4569
	centre no. 8	2.60	(-0.12, 5.32)	0.0607
	centre no. 9	-0.25	(-2.34, 1.85)	0.8163
	centre no. 10	-1.88	(-4.86, 1.10)	0.2169
	centre no. 11	-1.76	(-4.96, 1.45)	0.2825
	centre no. 12	0.50	(-2.89, 3.90)	0.7702
	centre no. 13	-0.50	(-2.46, 1.46)	0.6166
	centre no. 14	-1.13	(-4.17, 1.91)	0.4655
	centre no. 15	0.78	(-1.58, 3.13)	0.5176
	centre no. 16	1.75	(-0.18, 3.69)	0.0751
Sex (Ref.: Females)	Males	1.51	(0.42, 2.60)	0.0068
Therapy (ref: Methadone)	Buprenorphine	-1.35	(-2.73, 0.03)	0.0557
Education (ref: Primary)	Middle	-2.10	(-3.59, -0.61)	0.0058
	Vocational	-3.37	(-5.17, -1.56)	0.0003
	Secondary or higher	-4.23	(-6.03, -2.43)	<0.0001
Employment (ref: Employed)	Unemployed	0.48	(-0.59, 1.55)	0.3780
	Other	0.21	(-1.58, 1.99)	0.8210
Living status (ref: Parents)	Partner	4.85	(3.57, 6.13)	<0,0001
	Alone	2.25	(1.08, 3.53)	0,0002
	Friends	-1.62	(-4.54, 1.31)	0.2783
Partner (ref: No steady partner)	Steady and unmarried	-2.75	(-3.85, -1.65)	<0,0001
	Steady and married	-2.23	(-3.87, -0.59)	0.0076

† Coeff.: regression coefficient; ‡ 95% Confidence Interval; * p-value for the significance of the single factor.