Thyroid dysfunction linked to increased incident depressive events

Thyroid disorders are metabolic disorders affecting growth, and other metabolic activities. Studies suggest thyroid disease affect mood. Common thyroid disease symptoms that affect mood include anxiety or depression. In general, the more severe the thyroid disease, the more severe the mood changes.

However very few studies have examined thyroid disfunction and mood disorders longitudinally. Researchers in the current study assessed the cross-sectional and longitudinal association between thyroid function and depression in a population-based cohort.

The study published in The Journal of Clinical Endocrinology & Metabolism, found an association of thyroid function with the risk of developing depression, albeit small. Reverse causation and additional underlying factors may also contribute to the association reported the researchers.

A total of 9,471 individuals were included in cross-sectional analyses, of whom 8,366 had longitudinal data. At baseline, thyroid function using serum samples (thyrotropin (TSH), free thyroxine (FT4) and thyroid peroxidase antibodies (TPOAb)) and depressive symptoms using the Centre for Epidemiologic Studies Depression (CES-D) scale was assessed. Incident depressive events (N = 1,366) were continuously followed-up with the CES-D and clinical interviews. They analysed the cross-sectional association of thyroid function and thyroid disease with depressive symptoms using linear and logistic regression, and the longitudinal association with cox proportional hazard models for depressive events.

The key findings of the study are

• Lower TSH levels and lower and higher FT4 levels were cross-sectionally associated with more depressive symptoms with a B of -0.07 per one unit increase of natural log-transformed TSH (95% confidence interval -0.11; -0.04).

• Furthermore, hypothyroidism was cross-sectionally associated with less depressive symptoms and hyperthyroidism with more depressive symptoms.

• Longitudinally, there was a U-shaped association between FT4 and incident depressive events but only in euthyroid participants.

Researchers ended that “We show a cross-sectional association between thyroid (dys-)function with depressive symptoms, and a U-shaped association between FT4 and incident depressive events in euthyroid individuals. Our findings suggest an association of thyroid function with the risk of developing depression, albeit small. Reverse causation and additional underlying factors may also contribute to the association.”

Reference: Oscar Hernando Roa Dueñas, Amy Hofman, Annemarie I Luik, Marco Medici, Robin P Peeters, Layal Chaker, The Cross-sectional and Longitudinal Association Between Thyroid Function and Depression: A Population-Based Study, The Journal of Clinical Endocrinology & Metabolism, 2023;, dgad620, https://doi.org/10.1210/clinem/dgad620.