An Open Study of Triiodothyronine Augmentation of Selective Serotonin Reuptake Inhibitors in Treatment-Resistant Major Depressive Disorder

Objective: In an open trial, we investigated the efficacy of triiodothyronine (T₃) 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 T₃ 50 mg/day. Atypical and melancholic subtypes 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 T₃ 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 = 50%), and 6 subjects (30.0%) achieved clinical remission (final HAM-D-17 <= 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.