Table 3. Results of multinomial logistic regression of the factors affecting the use of opioid and amphetamine drugs^a .

Variable	Hard opioid, n= 764		Methamphetamine, n= 277		Methamphetamine + Hard opioid n= 219
	Adjusted OR (95%CI)	P value	Adjusted OR (95%CI)	P value	Adjusted OR (95% CI)	P value
Age
<30	1.16 (0.80 to 1.68)	0.444	1.23 (0.78 to 1.94)	0.386	1.81 (1.11 to 2.95)	0.018
30–39	1.00		1.00		1.00
40–49	0.74 (0.54 to 1.02)	0.062	0.71 (0.48 to 1.06)	0.098	0.64 (0.40 to 1.03)	0.066
≥50	0.43 (0.31 to 0.60)	<0.001	0.21 (0.12 to 0.36)	<0.001	0.30 (0.17 to 0.54)	<0.001
Marital status
Married	1.00		1.00		1.00
Unmarried	1.62 (1.28 to 2.06)	<0.001	1.50 (1.10 to 2.05)	0.011	3.34 (2.31 to 4.85)	<0.001
Occupation
Employed	1.00		1.00		1.00
Unemployed	1.82 (1.30 to 2.54)	0.001	1.60 (1.04 to 2.47)	0.033	3.07 (2.02 to 4.67)	<0.001
Subjective social status
Low	1.00		1.00		1.00
Middle	1.50 (1.17 to 1.92)	0.001	1.45 (1.05 to 2.01)	0.025	1.26 (0.88 to 1.80)	0.214
High	1.02 (0.77 to 1.59)	0.577	0.93 (0.57 to 1.51)	0.760	0.72 (0.41 to 1.26)	0.251
Age at initiation of current drug
<20	1.00		1.00		1.00
20-29	1.11 (0.78 to 1.57)	0.579	0.75 (0.49 to 1.14)	0.176	1.03 (0.64 to 1.66)	0.891
≥30	2.11 (1.40 to 3.20)	<0.001	1.14 (0.67 to 1.91)	0.632	1.92 (1.07 to 3.47)	0.030
Duration of the current drug use
<2.9	1.00		1.00		1.00
3-9.9	1.25 (0.94 to 1.68)	0.130	1.27 (0.87 to 1.86)	0.218	2.34 (1.52 to 3.60)	<0.001
≥10	1.65 (1.19 to 2.29)	0.002	1.49 (0.96 to 2.3)	0.072	2.31 (1.40 to 3.81)	0.001

^aThe use of soft opioids was set as the baseline level.

Goodness of fit indicators=Likelihood Ratio Test: χ²(df=33) = 211.03, P value ≤0.001. Pseudo R square= 0.12.