Does subclinical hypothyroidism have a role in the onset of depression?

Takeaway

• No association between subclinical hypothyroidism and incident depressive symptoms was observed in middle-aged participants.

Why this matters

Although several studies have shown positive effects of using thyroid hormone supplementation in the treatment of depression, the association between subclinical hypothyroidism and depressive symptoms and it remains controversial.

Study design

• Prospective cohort study of 92,206 participants (euthyroid, n=87,822; subclinical hypothyroidism, n=4384) without depression.
• Thyroid-stimulating hormone, free triiodothyronine and free thyroxin levels were assessed using electrochemiluminescent immunoassay, and depressive symptoms using the Center for Epidemiologic Studies-Depression score.
• Funding: None.

Key results

• There was no significant increase in risk for incident depressive symptoms among subclinical hypothyroid participants compared with and euthyroid participants (HR, 0.97; 95% CI, 0.87-1.09).
• No significant association between thyroid hormone levels and increased risk for incident depressive symptoms was observed in euthyroid patients (HR, 0.92; 95% CI, 0.86-0.99; P-trend=.09).

Limitations

• Self-reported questionnaires for identification of depressive symptoms.
• Short follow-up duration of the study.