2.1 Subjects
A total of 981 patients with MDD who were first hospitalized at Wuhan Mental Health Center from July 2017 to August 2022 were included.
Patients were eligible to meet the following inclusion criteria:
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Meet the diagnostic criteria for MDD in the 10th revision of the International Classification of Diseases (ICD-10).
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There was no history of hospitalization before the inpatient interview that day.
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Aged 18–60 years old, Chinese Han nationality.
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Their 17-item Hamilton Depression Scale (HAMD-17) total score needed to be ≥ 24.
Patients who meet one condition will be excluded:
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Breast-feeding patients are pregnant women.
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They have a history of material dependence.
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Patients with serious physical diseases or personality disorders.
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Patients with a clear history of diabetes mellitus in the past.
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Those who cannot cooperate with psycho-psychological related scales due to serious behavior disorders and other reasons.
The study was reviewed and approved by the Ethics Committee of Wuhan Mental Health Center, and all participants signed a written informed consent form. All participants have written informed consent signed by the patient himself or his family. Patients have the right to withdraw this study at any time.
2.2 Research design
This study was designed as a cross-sectional study. For the included MDD patients with initial hospitalization, we first calculated their prevalence of MetS, compared the differences in demographics and general clinical treatment between the two clinical subgroups with and without MetS, analyzed the factors associated with MetS, and the factors associated with MetS scores.
For MDD patients who met the inclusion criteria, we completed the collection of general clinical data on the day of the patient's visit, including age, gender, age of onset, course of disease, marital status, whether accompanied by suicidal behavior, and whether there is a history of outpatient treatment. At the same time, the patient's venous blood was collected to detect the patient's blood lipid profile (specifically: total cholesterol, TC; triglycerides, TG; low density lipoprotein cholesterol, LDL-C; high density lipoprotein cholesterol, HDL-C) level, fasting blood glucose (FBG) level, body mass index (BMI), blood pressure level (specifically: systolic blood pressure, SBP; diastolic blood pressure, DBP), and thyroid function (specifically: thyroid stimulating hormone, TSH; free triiodothyronine, FT3: Free triiodothyronine; FT4: free tetraiodothyronine) level. The severity of depressive symptoms was assessed using the Hamilton Depression Scale (HAMD-17), the severity of anxiety symptoms was assessed using the Hamilton Anxiety Scale (HAMA-14), the severity of psychotic symptoms was assessed using positive symptom subscale (PSS, a subscale of the Positive and Negative Symptom Scale, containing 7 items, items P1-P7, respectively), and the severity of pre-treatment illness was assessed using the Clinical Global Impression Scale (CGI).
Diagnostic criteria of metabolic syndrome: the diagnostic criteria for metabolic syndrome in China require that at least three of the following five indicators be met32: 1. abdominal obesity: waist circumference (WC) ≥ 90 cm in men and ≥ 85 cm in women. 2. hyperglycemia: FBG ≥ 6.1 mmol/L and/or those who have been diagnosed and treated for diabetes mellitus. 3. hypertension: SBP ≥ 130/85 mmHg or DBP ≥ 85 mmHg or confirmed and treated hypertension. 4. TG ≥ 1.70 mmol/L. 5. HDL-C < 1.04 mmol/L.
Scoring rules for MetS: based on previous studies, we have scored the severity of the MetS in including patients of the MetS33,34. According to the scoring rules, we first calculated the reciprocal of HDL-C and the mean arterial pressure (MAP) using the formula MAP =\(1/3\times SBP+2/3\times DBP\). Following this, we normalized the five MetS parameters: waist circumference (WC), triglycerides (TG), the reciprocal of HDL-C, fasting blood glucose (FBG), and MAP. Next, we performed a principal component analysis with varimax rotation on the five normalized components to derive principal components (PCs) with an eigenvalue of 1.0 or higher, which accounted for a substantial portion of the observed variation. In this study, PC1 and PC2 explained 25.23% and 20.85% of the variance, respectively [loadings PC1 (PC2): WC 0.26 (-0.63), TG 0.28 (0.50), HDL-C 0.17 (0.61), MAP 0.73 (0.04), and FBG 0.75 (-0.15)]. Finally, the weighted PC scores were determined by the relative weights of PC1 and PC2 in the explained variance. To obtain the MetS score, we added up the individual weighted PC scores.
The assessment of the relevant psychological scales was done by 2 uniformly trained psychiatrists with the title of attending or higher, belonging to the medical institution of the sample source.
2.3 Data analysis
The categorical variables are stated in terms of counts, while the data acquired for the normally distributed continuous measures are reported in terms of mean and standard deviation. T-tests on independent samples were employed to compare continuous variable from various groups. Chi-squared tests was used to compare rates. Then, the variables that differed in the univariate analysis were included in a binary logistic regression model as independent variables, with MetS as the dependent variable, to analyze the factors influencing MetS. The area under the receiver operating characteristics (AUCROC) was used to determine the discriminatory capacity of significant parameters to distinguish between patients with and without MetS. Finally, a multiple linear regression model was constructed with the MetS score as the outcome variable and the factors influencing MetS in binary logistic regression as the independent variables to determine the factors influencing the severity of MetS. All p values were 2- tailed, and the significance level was < 0.05. Statistical analyses were performed using SPSS 27 (SPSS, Inc., Chicago, IL).