Increased risk of hypothyroidism and hyperthyroidism in patients with major depressive disorder: a population-based study.

Objective: To determine the prevalence and incidence of hypothyroidism, hyperthyroidism, and risk factors in patients with major depressive disorder (MDD).

Methods: The National Health Research Institute provided a database of 1,000,000 random subjects for health service studies. We identified subjects aged ≥18 years who had at least 1 service claim during 2005 with a primary diagnosis of MDD or with a primary or secondary diagnosis of hypothyroidism or hyperthyroidism. We also compared the incidence of hypothyroidism and hyperthyroidism among patients with MDD and the general population from 2006 through 2010.

Results: The prevalence of hypothyroidism in patients with MDD was higher than that in the general population (1.20% vs. 0.30%; odds ratio, 3.08; 95% confidence interval, 2.35-4.03) in 2005. The prevalence of hyperthyroidism was also higher in patients with MDD than in the general population (2.46% vs. 0.79%; odds ratio, 2.77; 95% confidence interval, 2.29-3.35) in 2005. The annual incidence of hypothyroidism was higher in patients with MDD than that in the general population (0.40% vs. 0.13%; risk ratio, 2.47; 95% confidence interval, 2.00-3.06). The annual incidence of hyperthyroidism was also higher in patients with MDD than that in the general population (0.72% vs. 0.32%; risk ratio, 2.06; 95% confidence interval, 1.75-2.43).

Conclusions: Patients with MDD had a higher prevalence and a higher incidence of hypothyroidism or hyperthyroidism than the general population. Female sex was a risk factor for hypothyroidism and hyperthyroidism in MDD.