Thyroid Hormone Levels and Recurrence of Major Depression

OBJECTIVE: The relationship between basal thyroid hormone levels and acute antidepressant response has been studied, but any relationship between basal thyroid hormone levels and long-term course of depressive illness has not been evaluated. METHOD: The authors used a Cox regression survival analysis to evaluate the relationship between life course of depressive illness and basal levels of thyroid hormones (triiodothyronine [T3], thyroxine [T4,], and thyrotropin) in 75 outpatients with unipolar major depressive disorder. RESULTS: Time to recurrence of major depression was inversely related to T3 levels but not to T4 levels. CONCLUSIONS: These data may be of clinical interest in view of the fact that T3 is used to augment antidepressant response.