Increased Psychiatric Morbidity Before and After the Diagnosis of Hypothyroidism: A Nationwide Register Study

Background: Thyroid hormones are necessary for fetal brain development, and hypothyroidism in adults has been associated with mood symptoms and reduced quality of life. Nevertheless, our knowledge regarding the association and temporal relation between hypothyroidism and mental disorders is ambiguous. Our objective was to investigate, at a nationwide level, whether a diagnosis of hypothyroidism is associated with psychiatric morbidity. Methods: This is an observational cohort study. On the basis of record linkage between different Danish health registers, 2822 hypothyroid singletons each matched with 4 nonhypothyroid controls were identified and followed over a mean period of 6 years (range 1–13). Additionally, we included 385 same-sex twin pairs discordant for hypothyroidism. Diagnoses of psychiatric disorders as well as treatment with antidepressants, antipsychotics, and anxiolytics were recorded. Logistic and cox regression models were used to assess the risk of psychiatric morbidity before and after t...