Hyperthyroidism and suicide: a retrospective cohort study in Sweden

Objectives: Mental symptoms and impaired quality of life commonly occur in patients treated for hyperthyroidism. Our aim wits to determine whether a history of hyperthyroidism implies an increased risk of suicide. Design: Historic cohort study of 43 633 patients treated with radioiodine or surgery for hyperthyroidism between 1950 and 2005. The majority of the radioiodine-treated patients came from Stockholm. Two comparison cohorts consisted of 44 92 1 patients registered with an operation for atoxic nodular goitre between 1965 and 2005, and 354 861 patients with a cholecystectomy between 1965 and 2001. Methods: Subjects were followed from the date of diagnosis until death, emigration or end of follow-up. Information on outcome was obtained from population and health registers. Results: The number of observed suicide deaths was 134 in the study cohort. A naive comparison with the age-. sex- and calendar period-matched general Swedish population yielded it moderately increased standardized mortality ratio (SMR), but stratifications revealed that the excess was mainly driven by women from Stockholm. whose baseline suicide risk was higher than for women in the rest of Sweden. Using the population rates from Stockholm, the SMR among Stockholm women with Graves' disease was 1.14 (95% confidence intervals (CI) 0.66-1.86) and toxic goitre 0.99 (95% Cl 0.51-1.72). A direct comparison between the study cohort and the combined comparison cohorts, with multiple adjustments (including adjustment for residence in Stockholm), yielded a relative risk of suicide of 0.93 (0.68-1.26). Conclusions: This study did not confirm an increased risk of suicide among patients treated for hyperthyroidism.