Thyroid function within the normal range and the risk of depression: a population-based cohort study.

Area of Science:

• Endocrinology
• Geriatrics
• Psychiatry

Background:

• Overt thyroid dysfunction (hypo- and hyperthyroidism) is linked to depression risk.
• The impact of normal-range thyroid function on depression risk is not well understood.

Purpose of the Study:

• To investigate the association between normal-range thyroid function and the risk of depression in the elderly.

Main Methods:

• A cohort study of 1503 elderly individuals (mean age 70.6 years).
• Baseline assessments included serum TSH, thyroid peroxidase antibody levels, and depressive symptoms (CES-D).
• Follow-up monitored for incident depressive syndromes over a mean of 8.0 years.

Main Results:

• Individuals in the lowest normal TSH tertile (0.3-1.0 mU/L) had more depressive symptoms and a higher risk of depression compared to those in the highest tertile (1.6-4.0 mU/L).
• Prospectively, the lowest TSH tertile showed an increased risk of developing depressive syndromes.
• Thyroid autoimmunity was not associated with depressive symptoms or incident syndromes.

Conclusions:

• Low-normal TSH levels are associated with increased depressive symptoms and a higher risk of future depression in the elderly.
• This study highlights low-normal TSH as a crucial risk factor for depression in older populations.