Thyroid antibodies and depression: Is the relationship overstated?

Area of Science:

• Endocrinology
• Psychiatry
• Immunology

Background:

• Depression is frequently linked to Hashimoto's thyroiditis (HT).
• Thyroid antibodies are increasingly implicated in the pathophysiology of depression.
• This study investigates the association between thyroid antibodies and depressive symptoms.

Purpose of the Study:

• To examine the relationship between thyroid autoantibodies and depressive symptoms in euthyroid adults.
• To determine if thyroid peroxidase antibodies (TPOAb) or thyroglobulin antibodies (TgAb) are associated with depression severity.

Main Methods:

• Utilized data from 2897 euthyroid adults in the U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2012.
• Classified participants based on thyroid antibody status (TPOAb/TgAb).
• Employed survey-weighted linear regression and propensity score matching (PSM) to analyze associations with depressive symptoms (PHQ-9 scores).

Main Results:

• No significant differences in PHQ-9 depression scores were found between antibody-positive individuals and controls.
• Neither TPOAb nor TgAb positivity showed a significant association with depressive symptoms in unmatched or PSM analyses.
• Lower free T3 (FT3) levels within the normal range were inversely associated with PHQ-9 scores (β = -0.758, P = 0.01).

Conclusions:

• Thyroid autoantibody positivity (TPOAb, TgAb) is not significantly associated with depressive symptoms in euthyroid individuals.
• The observed inverse association between FT3 levels and depressive symptoms suggests a potential, albeit modest, relationship that requires further clinical investigation.
• Findings are limited by the cross-sectional design, representing single-time-point measurements.