Table 3.
Results of several Cox regression models for MDE onsetsa
| Variable | β (s.e.) | Hazard ratio: exp(β) |
(95% CI) | p |
|---|---|---|---|---|
| Model 1: Primary model | ||||
| CAR | 0.706 (0.241) | 2.030 | (1.260–3.250) | 0.003 |
| Slope | −0.234 (0.193) | 0.791 | (0.542–1.156) | 0.226 |
| AUCg | 0.030 (0.217) | 1.030 | (0.674–1.575) | 0.891 |
| CAR × time | −0.031 (0.013) | 0.969 | (0.946–0.993) | 0.012 |
| Model 2: Robustness test for the addition of baseline neuroticism | ||||
| CAR | 0.749 (0.262) | 2.114 | (1.264–3.535) | 0.004 |
| CAR × time | −0.032 (0.014) | 0.969 | (0.942–0.996) | 0.025 |
| Baseline neuroticism | 1.212 (0.238) | 3.360 | (2.106–5.359) | <0.001 |
| Model 3: Interaction with prospective major stressful life events | ||||
| CAR | 0.762 (0.269) | 2.143 | (1.265–3.631) | 0.005 |
| CAR × time | −0.034 (0.014) | 0.967 | (0.941–0.993) | 0.014 |
| Prospective events | 2.183 (0.376) | 8.876 | (4.250–18.539) | <0.001 |
| CAR × events | 0.164 (0.350) | 1.179 | (0.594–2.340) | 0.639 |
| Model 4: Interaction with MDE history | ||||
| CAR | 0.736 (0.281) | 2.088 | (1.205–3.619) | 0.009 |
| CAR × time | −0.034 (0.014) | 0.967 | (0.941–0.993) | 0.014 |
| MDE history | 1.291 (0.385) | 3.636 | (1.709–7.735) | 0.001 |
| CAR × MDE history | 1.162 (0.526) | 3.195 | (1.140–8.952) | 0.027 |
MDE, Major depressive episode; s.e., standard error; CI, confidence interval; CAR, cortisol awakening response; AUCg, area under the curve with respect to ground, or total waking cortisol.
a
All models include CAR, slope, AUCg and the CAR × time interaction as well as additional covariates for gender, Hollingshead socio-economic status index, African American race, Hispanic ethnicity, tobacco use, asthma, time of waking, hours of sleep, and hormonal contraceptive use. Continuous variables were entered in the model as z scores to aid interpretation; dichotomous variables (i.e. gender) were entered untransformed.