Participants
All patients were from the Department of Psychiatry, Frist Affiliated Hospital of China Medical University, and the inpatient department of the Mental Health Center of Shenyang. HCs were recruited by an advertisement in the community. All participants had to be confirmed by two trained psychiatrists using the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I). Patients with mood disorders were identified in accordance with the DSM-IV diagnostic criteria for MDD or BD, respectively, and did not meet the criteria for any other Axis I disorder. HC subjects had to have not had any current or lifetime Axis I Disorders, nor could they have had any first-degree relatives with a history of an Axis I disorder. All of the participants were assessed using the Hamilton Depression Rating Scale (HAMD) and Young Mania Rating Scale (YMRS). Exclusion criteria for the study were as follows: 1) must not have had a history of major physical disorders, particularly those that may be associated with brain tissue changes, such as hypertension, diabetes, or metastatic disease; 2) must not have had unstable diseases such as heavy asthma; neurological abnormalities, including major head trauma (loss of consciousness lasting more than 5 min), epilepsy, cerebrovascular disease, brain tumors, or neurodegenerative diseases; somatic diseases that may cause mood disorders, such as multiple sclerosis, thyroid disease, etc.; 3) no MRI contraindications; and 4) no lifetime or current substance dependence or abuse. All participants signed informed consent as approved by the Ethics Committee of China Medical University.
The study included 343 subjects aged 15–49 years divided into three groups: 70 patients with mood disorder and suicidal behavior (mean age: 27.529 ± 9.618 years; 55 females), 128 mood disorder patients without suicidal behavior (mood disorders control, MC) (mean age: 27.141 ± 8.318 years; 93 females), and 145 health control (HC) individuals (mean age: 27.833 ± 9.498 years; 96 females). Then, the patients with mood disorders and suicidal behavior were divided into two groups: Mood disorders with SI (SI defined as thoughts of engaging in behavior intended to end one’s life, assessed by the Beck 19-item Scale for Suicide Ideation [21]) and mood disorders with SAs (i.e., at least one attempt defined as a self-destructive act with some degree of intent to die [22]). Overall, 70 mood disorder patients with suicidal behavior were divided into two groups: 34 mood disorders with SI (mean age: 30.647 ± 10.141 years; 29 females) and 36 mood disorders with SAs (mean age: 24.583 ± 8.188 years; 26 females).
MRI acquisition
Scanning took place on a 3 T MRI scanner (General Electric, Milwaukee, USA) at the Image Institute of the First Affiliated Hospital of China Medical University, Shenyang, China. Earplugs and foam pads were used to minimize scanner noise and head motion. A standard head coil was used for radio frequency transmission and reception of the nuclear magnetic resonance signal. Three-dimensional, high- resolution, T1-weighted images were collected using a 3-D fast spoiled gradient-echo (FSPGR) sequence with the following parameters: TR/TE = 7.1/3.2 ms, image matrix = 240 × 240, field of view (FOV) = 240 × 240 mm2, 176 contiguous slices of 1 mm without gap, voxel size = 1.0 mm3. Participants were instructed to close their eyes, remain awake, and keep their mind blank during the resting state scan (after scanning we checked this with the subjects).
Data processing
Processing was performed using the DARTEL algorithm Statistical Parametric Mapping software (SPM8, http://www.fil.ion.ucl.ac.uk/spm/software/spm8/) under the MATLAB R2010b platform (Mathworks, Sherborn, MA, USA). Segmentation function was used to divide the regions into gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) using the ‘new segment’ tool implemented in SPM8. During spatial normalization, inter-subject registration was achieved using respective registration based on group assignment. A modulation step was used to ensure that the overall amount of tissue in a class was unaltered. The segmented images were normalized to the Montreal Neurological Institute (MNI) template and were smoothed with an 8-mm full width at half-maximum (FWHM) Gaussian filter. The voxel size of data acquisition was 1 mm3 and the voxel size of normalized data was 1.5 mm3.
Statistical analyses
Three-group (mood disorders with suicidal behavior, MC, and HC) analyses of GM volumes were performed in SPM8 using ANCOVA with a diagnostic group as an independent factor and age and gender as covariates. Statistical significance was set at significant inference of P < 0.01 with Family Wise Error (FWE) correction. An extent threshold of 10 voxels was considered significant among the three groups. We then extracted GMV values for each cluster with significant differences for the three-group comparison and conducted pairwise two sample t-tests, corrected for multiple comparisons (P < 0.05, Least Significant Difference [LSD] test).
The demographic and clinical characteristics of the subjects were analyzed using IBM SPSS Statistics for Windows, Version 22.0 (Armonk, NY, USA). Student's t-tests, one-way analyses of variance, or Chi-square tests were used depending on the normality of distribution and type of data. Categorical variables were described using frequencies and proportions. Continuous variables were presented as mean ± standard deviation. Statistical significance was determined by P < 0.05.