Table 2. The First Step of the Cox Model Assesses the Predictive Value of Lifetime History of Methamphetamine use (total uses), Days Since Last Use and Risk-taking Behavior.
| −2 Log likelihood |
Overall |
Change from previous step |
||||
|---|---|---|---|---|---|---|
| χ2 | df | p-Value | Δχ2 | df | p-Value | |
| Model without insula | ||||||
| 141.8 | 2.3 | 3 | 0.52 | 2.3 | 3 | 0.51 |
| Predictor | B | SE | p-Value | Odds ratio |
|---|---|---|---|---|
| Variables in the equation | ||||
| Methamphetamine use | −0.36 | 0.25 | 0.15 | 0.70 |
| Days since last use | 0.07 | 0.21 | 0.73 | 1.07 |
| Risk-taking | −0.002 | 0.25 | 0.99 | 0.99 |
| −2 Log likelihood |
Overall |
Change from previous step |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| χ2 | df | p-Value | Δχ2 | df | p-Value | ||||
| Step 2 including insula | |||||||||
| 128.9 | 12.6 | 4 | 0.01 | 12.9 | 4 | <0.01 |
| Predictor | B | SE | p-Value | Odds ratio |
|---|---|---|---|---|
| Variables in the equation | ||||
| Methamphetamine use | −0.33 | 0.26 | 0.21 | 0.72 |
| Days since last use | 0.28 | 0.22 | 0.19 | 1.3 |
| Risk-taking | −0.26 | 0.27 | 0.33 | 0.77 |
| Right insula (risk–safe) | −1.1 | 0.33 | 0.001 | 0.34 |
In the second step, right insula is added. Right insula represents average activation during a risky decision minus activation during a safe decision, reflecting the differential activation between risk and safe.