Prevalence and Risk Factors of Subclinical Hypothyroidism in Young and Middle-Aged Patients With First-Episode Drug-Naïve Major Depressive Disorder.

Subclinical hypothyroidism (SCH) is a mild impairment of thyroid function. The prevalence of SCH is significantly higher in the major depressive disorder (MDD) population than in the general population, but the risk factors and relationships are not apparent. The occurrence of SCH is influenced by age and medication. Therefore, our study was to investigate the prevalence and risk factors of SCH in young and middle-aged groupstotal of patients with first-episode and drug-naive (FEDN) MDD. A total of 1717 FEDN MDD patients were divided into a younger group (18-45 years) and a middle-aged group (>45 years). The Hamilton Depression Scale (HAMD) was used to assess patients' depression symptoms. Serum thyroid function and lipid level parameters were measured. A self-administered questionnaire collected other clinical and demographic data. The prevalence of SCH in middle-aged MDD patients was 66.9%. Middle-aged patients had a longer duration of illness, a later age of onset, a higher proportion of female patients, and a lower level of education. Further logistic regression indicated that serum total cholestrol (TC) and high-density lipoprotein cholesterol (HDL-C) levels, as well as overweight and obesity, were significantly associated with SCH in both groups; however, low-density lipoprotein cholesterol (LDL-C) was an independent risk factor associated with SCH in the middle-aged group. Our results suggest that the prevalence of SCH is higher in middle-aged MDD patients than in younger patients and that long-term more severe depression, high TC and HDL-C levels, and abnormal body weight may influence the occurrence of SCH. Physicians should pay more attention to LDL-C levels in middle-aged patients with FEDN MDD.