Table 6.
Evidence for predictive validity: Prediction of abstinence from marijuana use and related problems and symptoms at 12 months from 6-month readiness
| Variable | 6RR |
6SA |
6SR |
6STS |
||||
| Estimate | SE | Estimate | SE | Estimate | SE | Estimate | SE | |
| 12-month PDA | ||||||||
| Fixed effects | ||||||||
| Sex (1 = female, 2 = male) | −1.85 | 7.84 | −5.66 | 6.71 | −5.55 | 6.82 | −3.92 | 6.69 |
| Age | −1.00 | 2.94 | 0.95 | 2.61 | 0.70 | 2.66 | 0.65 | 2.59 |
| Race (1 = White, 2 = other) | −14.17 | 10.78 | −15.72 | 9.38 | −16.50 | 9.55 | −18.12 | 9.34 |
| ADT: #inpt. + #residential days, last 30 days | 1.42 | 0.87 | 1.43 | 0.69* | 1.31 | 0.70 | 1.23 | 0.68 |
| 6-month PDA, last 30 days | 0.37 | 0.11** | 0.30 | 0.12* | 0.50 | 0.07** | 0.37 | 0.09** |
| 6-month readiness | 2.50 | 1.46 | 8.23 | 3.84* | 0.66 | 2.81 | 8.04 | 3.06** |
| Random effects | ||||||||
| Intercept (site differences) | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Residual | 1,456.81 | 192.96** | 1,346.73 | 162.13** | 1,400.06 | 167.94** | 1,334.25 | 160.05** |
| n | 114 | 138 | 139 | 139 | ||||
| 12-month RMPI | ||||||||
| Fixed effects | ||||||||
| Sex | 0.47 | 0.38 | 0.47 | 0.33 | 0.58 | 0.34 | 0.45 | 0.33 |
| Age | −0.10 | 0.14 | −0.11 | 0.13 | −0.05 | 0.13 | −0.07 | 0.13 |
| Race | 0.00 | 0.52 | 0.36 | 0.45 | 0.67 | 0.47 | 0.64 | 0.45 |
| ADT | 0.09 | 0.04* | 0.05 | 0.03 | 0.04 | 0.03 | 0.05 | 0.03 |
| 6-month RMPI | 0.07 | 0.01** | 0.07 | 0.01** | 0.08 | 0.01** | 0.08 | 0.01** |
| 6-month readiness | −0.18 | 0.06** | −0.48 | 0.11** | 0.08 | 0.15 | −0.34 | 0.12** |
| Random effects | ||||||||
| Intercept | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Residual | 3.23 | 0.44** | 2.92 | 0.36** | 3.27 | 0.40** | 3.09 | 0.38** |
| n | 106 | 129 | 131 | 131 | ||||
| 12-month DSMS | ||||||||
| Fixed effects | ||||||||
| Sex | 0.50 | 0.34 | 0.33 | 0.28 | 0.40 | 0.29 | 0.32 | 0.29 |
| Age | 0.06 | 0.13 | 0.05 | 0.11 | 0.09 | 0.11 | 0.08 | 0.11 |
| Race | 0.07 | 0.45 | 0.22 | 0.38 | 0.35 | 0.40 | 0.34 | 0.39 |
| ADT | 0.03 | 0.04 | 0.02 | 0.03 | 0.02 | 0.03 | 0.02 | 0.03 |
| 6-month DSMS | 0.39 | 0.08** | 0.38 | 0.07** | 0.48 | 0.07** | 0.46 | 0.07** |
| 6-month readiness | −0.13 | 0.05** | −0.35 | 0.10** | 0.06 | 0.12 | −0.20 | 0.11 |
| Random effects | ||||||||
| Intercept | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Residual | 2.59 | 0.35** | 2.27 | 0.27** | 2.43 | 0.29** | 2.38 | 0.29** |
| n | 112 | 136 | 138 | 138 | ||||
Notes: ns differ because of missing data, and parameter estimates are unstandardized. A square root transformation was applied to the Rutgers Marijuana Problem Index (RMPI) and alcohol and other drug treatment (ADT) data. 6RR = 6-month Readiness Ruler; 6SA = 6-month Staging Algorithm; 6SR = 6-month SOCRATES Recognition; 6STS = 6-month SOCRATES Taking Steps; PDA = percentage of days abstinent, measured by use of the Timeline Followback Interview and references 30 days before the interview date; inpt. = inpatient; DSMS = Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, marijuana abuse and dependence symptom count.
p≤.05;
p≤.01.