BackgroundWe previously reported that depressive personality (the scores of hypochondriasis, depression and psychasthenia determined by the Minnesota Multiphasic Personality Inventory (MMPI)) and daily hassles of Graves' disease (GD) patients treated long trem with antithyroid drug (ATD) were significantly higher in a relapsed group than in a remitted group, even in the euthyroid state. The present study aims to examine the relationship among depressive personality, emotional stresses, thyroid function and the prognosis of hyperthyroidism in newly diagnosed GD patients.MethodsSixty-four untreated GD patients responded to the MMPI for personality traits, the Natsume's Stress Inventory for major life events, and the Hayashi's Daily Life Stress Inventory for daily life stresses before and during ATD treatment.ResultsIn the untreated thyrotoxic state, depressive personality (T-scores of hypochondriasis, depression or psychasthenia greater than 60 points in MMPI) were found for 44 patients (69%). For 15 (23%) of these patients, the scores decreased to the normal range after treatment. However, depressive personality persisted after treatment in the remaining 29 patients (46%). Normal scores before treatment were found for 20 patients (31%), and the scores were persistently normal for 15 patients (23%). The remaining 5 patients (8%) had higher depressive personality after treatment. Such depressive personality was not associated with the severity of hyperthyroidism. Serum TSH receptor antibody activity at three years after treatment was significantly (p = 0.0351) greater in the depression group than in the non- depression group. The remission rate at four years after treatment was significantly (p = 0.0305) lower in the depression group than in the non- depression group (22% vs 52%).ConclusionThe data indicate that in GD patients treated with ATD, depressive personality during treatment reflects the effect of emotional stress more than that of thyrotoxicosis and that it aggravates hyperthyroidism. Psychosomatic therapeutic approaches including antipsychiatric drugs and/or psychotherapy appears to be useful for improving the prognosis of hyperthyroidism.