The Association Between Thyroid Stimulating Hormone and Depression: A Historical Cohort Study

Area of Science:

• Endocrinology
• Psychiatry
• Population Health

Background:

• Thyroid hormones play a crucial role in regulating mood and cognitive function.
• Suboptimal thyroid function is increasingly recognized as a potential contributor to mood disorders.
• Understanding the relationship between thyroid-stimulating hormone (TSH) and depression is vital for comprehensive patient care.

Purpose of the Study:

• To examine the association between TSH levels and clinically relevant depression (CRD) in a diverse patient population.
• To determine if TSH levels correlate with the presence and severity of depressive symptoms.
• To identify potential risk factors for depression related to thyroid function.

Main Methods:

• A retrospective analysis of 29,034 adult patients from Mayo Clinic (July 2017 - August 2021).
• Patients with concurrent TSH and Patient Health Questionnaire-9 (PHQ-9) scores were included.
• Logistic regression was used to assess the association between TSH categories (low, normal, high) and CRD (PHQ-9 ≥ 10), with adjustments for covariates.

Main Results:

• The study cohort had a mean age of 51.4 years, with 65% females and a mean TSH of 3.0±8.5 mIU/L.
• A TSH level below 0.3 mIU/L was significantly associated with higher odds of CRD (OR, 1.37; 95% CI, 1.18-1.57; P<.001) compared to normal TSH levels.
• This association was particularly noted in individuals aged 70 years or younger; no increased odds of CRD were observed in patients with subclinical or overt thyroid dysfunction.

Conclusions:

• Low TSH levels are associated with an increased likelihood of clinically relevant depression in a large, population-based study.
• The findings suggest a potential link between thyroid function and mood regulation that warrants further investigation.
• Longitudinal studies are recommended to explore the causal relationship between thyroid dysfunction and depression, including potential sex differences.