Abstract
We investigated the relationship between thyroid function and the response to antidepressant drugs in patients experiencing a depressive episode by a logistic regression analysis in order to identify independent predictors of the outcome. The study sample consisted of 46 patients between the ages of 18 and 84 years with a definite diagnosis of a depressive episode of a major depressive disorder or bipolar disorder (Diagnostic and Statistical Manual for Mental Disorder, IVed.) . We administered pharmacotherapy with antidepressant drugs to the patients for 12 weeks. At the commencement of pharmacotherapy (week 0), and 12 weeks thereafter (week 12), the levels of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) in the serum were measured and a test using the 17-item Hamilton Rating Scale for Depression (HRSD-17) was performed. The patients were divided into two groups: the good-outcome group (25 patients) based on at least 50% improvement in the HRSD-17 score as defined as responders and the poor-outcome group (21 patients) (<50%) as nonresponders. A logistic regression analysis revealed that the serum FT4 level at week 0 significantly correlated with the treatment outcome (odds ratio 43.4 ; 95% confidence interval 1.33 to 1413.26; p=0.03) . In both the responders and nonresponders, there were significant reductions in the FT4 level between week 0 and week 12. In responders, the degree of decrease in the serum FT4 levels from week 0 to week 12 was significantly greater than that in the nonresponders (df=44, F=0.39, p=0.007) . These results suggest that the serum FT4 level before treatment is a prognostic factor for antidepressant treatment and that it decreases as depression improves.
