Neuroendocrine aspects of primary endogenous depression. VII. Logistic regression analysis of matched patient-control...

We previously reported significant alterations in hypothalamo-pituitary-adrenal cortical (HPA) and thyroid (HPT) axis function in a group of 40 primary, RDC definite endogenous depressives compared to 40 individually matched normal control subjects. In those reports, univariate statistical tests for matched samples were used (paired t-tests). We next wished to use both the HPA and the HPT measures in a multivariate analysis to discriminate the patients from the controls, but the paired nature of the hormone data obviated the use of standard techniques. With an adaptation of the BMDP PLR statistical program, we performed a matched logistic regression analysis, in stepwise fashion, which resulted in a model incorporating two HPA variables and one HPT variable. From this model, odds ratios which associate being depressed or not with levels of the HPA and HPT measures were estimated. The median odds ratio for the 40 matched pairs was 7.8. To illustrate the model, we present graphs of estimated odds ratios of patients with selected hormone values compared to a typical normal subject with hormone values close to the median values of the 40 controls in our study.