Thyroid antibodies and depression: Is the relationship overstated?

Depression has been associated with Hashimoto's thyroiditis (HT), with growing evidence suggesting that thyroid antibodies may play a role. This study aimed to explore this potential link.

Data from 2897 euthyroid adults in NHANES 2007-2012 were classified by thyroid antibody status (TPOAb/TgAb). Associations with depressive symptoms (PHQ-9 scores) were evaluated using survey-weighted linear regression and adjusted via propensity score matching (PSM).

Although thyroid hormone levels (FT3, FT4, and TSH) significantly differed across antibody-defined groups, no significant differences in PHQ-9 depression scores or symptom severity were observed between antibody-positive individuals and controls. TPOAb and TgAb positivity were not significantly associated with depressive symptoms in either the unmatched or propensity score-matched analyses. TgAb levels showed a statistically significant but negligible association with PHQ-9 scores (β = -0.002, P = 0.04). In contrast, FT3 levels were inversely associated with PHQ-9 scores (β = -0.758, P = 0.01), indicating a modest relationship between lower FT3 concentrations (within the normal range) and more severe depressive symptoms.

Cross-sectional design limits findings to single-time-point measurements, and results are based on a U.S.

In this nationally representative sample of euthyroid individuals, thyroid autoantibody positivity, whether TPOAb, TgAb, or both, was not significantly associated with presence of depressive symptoms. Although lower FT3 levels within the normal range were inversely associated with PHQ-9 scores, the clinical significance of this finding warrants further investigation.