Objective: Endocrine dysfunction may produce symptoms that are difficult to distinguish from the clinical manifestations of psychiatric disorders. In particular, the function of the hypothalamic - pituitary - thyroidal axis is known to be associated with a number of psychiatric abnormalities, such as depression and anxiety. In this study, we tested the hypothesis that depression is more commonly encountered in hypothyroidism, while anxiety is more prevalent in hyperthyroidism. Additionally, we aimed to evaluate the correlations of the intensity of the psychiatric symptomatology in these patients with the specific parameters of thyroid function, such as levels of TSH, T3 and T4. Method: Patients newly diagnosed as having thyroid disorders were included in the study. They were classified into five study groups ( according to the results of thyroid-stimulating hormone ( TSH), free triiodothyronine (fT3), free thyroxine (fT4) and autoantibody (anti-thyroglobulin antibodies and anti-microsomal antibodies) measurements): hypothyroid, hyperthyroid, subclinical hypothyroid, subclinical hyperthyroid, and euthyroid Hashimoto's thyroiditis. Psychopathological symptoms were evaluated on the 17-item Hamilton Rating Scale for Depression (HDRS), Brief Symptom Inventory ( BSI), BSI Sub-scales and Hospital Anxiety and Depression Scale ( HAD). Psychiatric diagnoses were performed using DSM-IV-SCID ( Structured Clinical Interview for DSM). The relationship between the results of the psychiatric evaluation and thyroid function tests was assessed statistically by ANOVA and Pearson correlation tests. Results: Eighty patients ( 68 female and 12 male), with a mean age of 42.5 +/- 13.4 years, were evaluated. A positive correlation between the total BSI scores and TSH levels ( r = 0.65, P = 0.01) was noted in the hypothyroid ( n = 25) group. Hyperthyroid patients ( n = 22) showed a positive correlation between HDRS scores and fT4 levels ( r = 0.62, P = 0.01). The BSI scores in hypo- and hyperthyroidism were significantly higher than normal ( P< 0.05). In the subclinical hypothyroid ( n = 7), subclinical hyperthyroid ( n = 11), and euthyroid Hashimoto's thyroiditis ( n = 15) groups no correlation was found between thyroid function tests and HDRS, BSI, and HAD scores. Conclusion: The results indicate that patients with thyroid disorders have high levels of anxiety and depressive symptoms. Thirty-five patients (43%) out of 80 had an axis I psychiatric disorder. However, our findings did not support an association between high levels of depression and hypothyroidism or between high levels of anxiety and hyperthyroidism. Moreover, this study did not reveal any specific psychiatric manifestation of hypothyroidism or hyperthyroidism.