Objective: In an open trial, we investigated the efficacy of triiodothyronine (T(3)) adjuvant to selective serotonin reuptake inhibitors (SSRIs) in subjects with major depressive disorder (MDD) resistant to SSRI treatment.
Method: Twenty subjects who met DSM-IV criteria for MDD (mean +/- SD age = 44.3 +/- 10.3 years; 55% [N = 11] women) and had failed to respond to a course of treatment of at least 8 weeks with an SSRI antidepressant were enrolled in a 4-week open-label augmentation treatment with T(3) 50 microg/day. Atypical and melancholic sub-types of MDD were diagnosed using Structured Clinical Interview for DSM-IV Axis I Disorders criteria. We administered the 17-item Hamilton Rating Scale for Depression (HAM-D-17) 4 times during the study (which was conducted between 2001 and 2003).
Results: During T(3) augmentation, the severity of depression decreased from an initial mean +/- SD HAM-D-17 score of 20.5 +/- 3.6 to a final HAM-D-17 score of 14.0 +/- 7.1 (p < .001). Seven subjects (35.0%) were treatment responders (HAM-D-17 reduction >or= 50%), and 6 subjects (30.0%) achieved clinical remission (final HAM-D-17 <or= 7). The 5 subjects with atypical depression experienced significantly (p < .01) greater clinical improvement (final HAM-D-17 scores 6.6 +/- 1.8 vs. 16.4 +/- 4.5), and higher rates of treatment response (100% [5/5] vs. 13.3% [2/15]) and remission (80.0% [4/5] vs. 13.3% [2/15]), compared to subjects with nonatypical MDD. The 8 subjects with melancholic MDD experienced significantly (p < .05) greater depression severity at the end of the study compared to nonmelancholic MDD subjects (final HAM-D-17 scores = 18.3 +/- 6.6 vs. 11.1 +/- 6.1).
Conclusion: Triiodothyronine augmentation of SSRIs may be a promising treatment strategy in SSRI-resistant MDD, particularly in subjects with the atypical MDD subtype.