An association between depression, anxiety and thyroid function - a clinical fact or an artefact?

Objective: The aim of the study was to examine the association between depression, anxiety and thyroid dysfunction. Method: The study is part of the HUNT-study. Individuals aged 40-89 years (n =30 589) with thyroid assays, and self-rating of depression and anxiety - Hospital Anxiety and Depression Scale (HADS) - were divided in six categories according to thyroid function. Relations were investigated with logistic regression analysis. Results: The group with biochemical hypothyroidism had significantly lower risk for depression and anxiety compared with the reference group with normal thyroid function. Subclinical hypothyroidism, and latent and overt biochemical hyperthyroidism were not risk factors for depression or anxiety. When individuals with former known thyroid disease were excluded from the analyses, the results were essentially identical, but this group had an increased risk of both anxiety and depression, independent of thyroid function. Conclusion: In this large, unselected population, we found no statistical association between thyroid dysfunction, and the presence of depression or anxiety disorder.