Association Between Thyroid Function Markers (TSH, Free T4) and Depression Severity Assessed by PHQ-9 in Hypothyroidism: An Analytical Approach

Abstract

Introduction: Hypothyroidism and depression frequently co-occur, but the mechanistic links between thyroid biomarkers and depressive symptoms remain debated.

Objective: To investigate the association between thyroid function markers (TSH, free T4) and depression severity in hypothyroid patients.

Methods: A cross-sectional, observational study was conducted in an adult hypothyroid cohort, utilizing biochemical markers and validated psychiatric assessments (PHQ-9). Descriptive statistics, correlation coefficients, and multiple regression models were used to analyze the relationship between thyroid function and depression severity.

Results: The study found a modest but statistically significant positive correlation between TSH levels and depression severity (r≈0.30-0.42, p<0.001), with mean TSH levels rising progressively as depression severity increased. Free T4 levels showed a weak negative correlation with PHQ-9 scores. Subgroup analyses revealed more pronounced correlations in younger adults and females.

Conclusion: This study demonstrates a link between thyroid function and depression severity in hypothyroid patients, particularly in high-risk demographics. Routine thyroid function testing and integrated management approaches are recommended. Further longitudinal studies are necessary to clarify causality and develop targeted interventions.