Table 2.

Survival Analysis Results From Cox Proportional Hazards Regression Model^*

Model	Hazard Ratio (95% CI)	P Value
Model 1
Treatment†	1.13 (0.69–1.36)	.62
Model 2
Treatment‡	1.18 (0.71–1.94)	.53
Psychosis‡	0.56 (0.32–1.00)	.05
Age§	0.99 (0.97–1.00)	.13
Sex‖	0.63 (0.37–1.08)	.09

Abbreviations: C-ECT, continuation electroconvulsive therapy; C-Pharm, combination of lithium carbonate plus nortriptyline hydrochloride; CI, confidence interval.

^*Results are presented for 2 Cox proportional hazards regression models. Model 1 contained treatment, and model 2 (adjusted model) contained treatment, psychosis, age, and sex. Model 2 also contained clinical center as a covariate.

^†Reference category was C-Pharm; hazard ratio of relapse for C-ECT compared with C-Pharm. The C-ECT group was 1.2 times more likely to relapse than C-Pharm group.

^‡Reference category was no psychosis; hazard ratio of relapse for psychosis compared with no-psychosis group. A patient with psychotic features is 0.56 times less likely to relapse than a patient without psychotic features, after adjustment for treatment, age, sex, and center.

^§Age was entered as a continuous variable; hazard ratio represents the change in the hazard of relapse for every 1-year increment (decrement) in age. As age increases by 1 year, the estimated hazard ratio is decreased (since the parameter estimate is negative) 0.99 times.

^‖Reference category was male; hazard ratio of relapse for female compared with male group. A female patient is 0.63 times less likely to relapse than a male patient after adjustment for treatment, age, psychosis, and clinical center.