Table 1 Demographic characteristics in the methamphetamine-only, heroin-only, and polysubstance groups
| Â | Methamphetamine-only | Heroin-only | Poly-substance | P value |
|---|---|---|---|---|
(N = 232) | (N = 843) | (N = 411) |  | |
Provinces |  |  |  |  < 0.001 |
  Sichuan | 13 (5.6%) | 66 (7.8%) | 120 (29.2%) |  |
  Shaanxi | 39 (16.8%) | 206 (24.4%) | 94 (22.9%) |  |
  Qinghai | 101 (43.5%) | 167 (19.8%) | 91 (22.1%) |  |
  Gansu | 23 (9.9%) | 254 (30.1%) | 51 (12.4%) |  |
  Ningxia | 56 (24.1%) | 150 (17.8%) | 55 (13.4%) |  |
Gender | Â | Â | Â | 0.002 |
  Male | 189 (81.5%) | 750 (89.0%) | 344 (83.7%) |  |
  Female | 43 (18.5%) | 93 (11.0%) | 67 (16.3%) |  |
Age, years | 31.26 ± 8.02 | 43.46 ± 7.65 | 34.13 ± 9.53 |  < 0.001 |
Ethnicity | Â | Â | Â | 0.005 |
  Han | 168 (72.4%) | 649 (77.0%) | 341 (83.0%) |  |
  Minority | 64 (27.6%) | 194 (23.0%) | 70 (17.0%) |  |
Full-time education | Â | Â | Â | 0.03 |
  ≤ 9 years | 184 (79.2%) | 632 (75.0%) | 288 (70.1%) |  |
  > 9 years | 48 (20.8%) | 211 (25.0%) | 123 (29.9%) |  |
Employment status |  |  |  |  < 0.001 |
  Not employed | 113 (48.7%) | 540 (64.1%) | 232 (56.4%) |  |
  Employed | 119 (51.3%) | 303 (35.9%) | 179 (43.6%) |  |
Initial age of substance use, years | 23.98 ± 8.06 | 35.44 ± 9.63 | 26.86 ± 9.91 |  < 0.001 |
Substance use duration, years | 7.28 ± 5.85 | 8.01 ± 6.34 | 7.27 ± 5.82 | 0.18 |
Substance addiction duration, years | 4.35 ± 4.50 | 4.99 ± 5.54 | 4.73 ± 5.08 | 0.82 |