Purpose: Associations between thyroid diseases and depression have been described since the 1960s but there is a lack of population-based studies investigating associations of thyroid diseases with depression and anxiety defined by gold-standard methods. Thus, the aim was to investigate the association of diagnosed thyroid disorders, serum thyroid-stimulating hormone (TSH) levels, and anti-thyroid-peroxidase antibodies (TPO-abs) with depression and anxiety.
Methods: We used data from 2142 individuals, who participated in the first follow-up of the Study of Health in Pomerania (SHIP-1) and in the Life-Events and Gene-Environment Interaction in Depression (LEGEND). DSM-VI diagnoses of major depression disorder and anxiety were defined using the Munich-Composite International Diagnostic Interview; the Beck depression inventory (BDI-II) was used for the assessment of current depressive symptoms. Thyroid diseases were assessed by interviews and by biomarkers and were associated with depression and anxiety using Poisson regression adjusted for age, sex, marital status, educational level, smoking status, BMI, and the log-transformed time between SHIP-1 and LEGEND.
Results: Untreated diagnosed hypothyroidism was positively associated with the BDI-II-score and with anxiety, while untreated diagnosed hyperthyroidism was significantly related to MDD during the last 12 months. Serum TSH levels and TPO-Abs were not significantly associated with depression and anxiety. In sub-analyses, distinct interactions were found between childhood maltreatment and thyroid disorders in modifying the association on depression and anxiety disorders.
Conclusions: Our results substantiate evidence that diagnosed untreated hypothyroidism is associated with depression and anxiety, and that diagnosed untreated hyperthyroidism is associated with depression.
Keywords: Anxiety; Depression; Epidemiology; Thyroid; Thyroid hormone metabolism.