Depressive symptoms, thyroid hormone and autoimmunity in a population-based cohort from Sardinia.

Objective: Toevaluatetheassociationbetweendepressivesymptomsandthyroidautoimmunity,andthe effect ofthyroidhormoneontheriskofdepression. Methods: Weincluded3138individualsfromSardiNIAproject,noneofwhomwastakingthyroid medication andantidepressants.Thyrotropin(TSH),freethyroxine(FT4),andantibodiesagainstthyr- operoxidase(TPOAb)weremeasuredinallthesample.DepressivesymptomswereassessedwithCenter for EpidemiologicStudiesDepressionScale(CES-D). Results: WefoundnoassociationbetweenTPOAbanddepressivesymptomsandnolinearassociation between TSHorFT4levelsanddepressivesymptoms.However,individualsinthelowestandhighestFT4 quintilesshowedahigherCES-Dscorecomparedtoindividualsinthemiddlequintile.Inaddition, participants inthelowestandhighestFT4quintileshadanincreasedriskofCES-DZ16withoddsratios of 1.44(95%CI¼1.09-1.89)and1.33(95%CI¼1.011.77),respectively. Limitations: Cross-sectional designofthestudy. Conclusions: A U-shapedrelationwasfoundbetweenFT4anddepressivesymptoms:comparedto averageFT4values,bothhighandlowthyroidfunctionwasassociatedwithmoredepressivesymptoms. Further studiesarenecessarytodeterminetheexactcause-effectrelationofthisassociation.