Psychiatric manifestations of thyroid dysfunction in adults

Thyroid dysfunction is common in adults and has clinically relevant psychiatric manifestations. Clarifying which thyroid phenotypes are linked to depression and anxiety can inform screening and management. We conducted a PRISMA-guided systematic review of peer-reviewed studies in adults assessing psychiatric outcomes in overt and subclinical hypo and hyperthyroidism and autoimmune thyroiditis, compared with euthyroid or general-population controls. Observational designs (cohort, case-control, cross-sectional) and trials were eligible. Two reviewers performed study selection, data extraction, and risk-of-bias appraisal with standardized tools. Ten studies met inclusion criteria (two nationwide registry cohorts, one prospective cohort, one case-control, six cross-sectional). Across registry cohorts, risks of psychiatric diagnoses and initiation of antidepressants, anxiolytics were elevated around the time of thyroid disease diagnosis, with some excess risk observed pre-diagnosis and persisting after treatment. In clinical comparisons, patients with Graves' disease reported higher anxiety burden than those with nodular goitre, and untreated hypothyroidism correlated with greater depressive symptoms and anxiety disorders. Evidence for subclinical hypothyroidism was mixed in community cohorts and did not consistently predict incident depression. In euthyroid autoimmune thyroiditis, case-control data showed higher odds of mood and anxiety disorders versus matched controls, suggesting immune mechanisms independent of frank hormone derangement. Overt thyroid disorders and autoimmune thyroiditis show the clearest associations with depressive and anxiety outcomes, while links with subclinical dysfunction are heterogeneous. Routine mental-health screening is warranted in overt disease and autoimmune thyroiditis, alongside individualized endocrine management.