2.7. Statistical analysis

Statistical analysis was conducted using the SPSS software (version 26.0, SPSS Inc., Armonk, NY, United States). To compare the demographic characteristics between the depressed patients and HCs, χ² tests were used for gender and marital status, whereas independent sample t-tests were used for age and education level. Paired sample t-tests were performed to compare the differences in the scores of HAMD-17 and BSSI before and after ECT treatment in the patients.

The Statistical Analysis module in the DPABI V7.0 toolbox was used to analyze the ALFF and fALFF values and ReHo. Independent sample t-tests were adopted to assess the differences in ReHo and ALFF/fALFF values between HCs and patients. Paired t-tests were used to compare ReHo and ALFF/fALFF values before and after ECT treatment in patients. Head motion parameters (Mean FD_Jenkinson) were included as covariates in the analysis. The significance level for this study was set at p < 0.05 (two-tailed), with Gaussian random field (GRF) correction applied. The ROI Signal Extractor module in the DPABI V7.0 toolbox was used to extract statistically significant brain regions. Correlation coefficients among ReHo, ALFF/fALFF, HAMD-17 scores, and BSSI scores were calculated using the Pearson test. The significance level was set at p < 0.05 (two-tailed). Alterations in HAMD-17 (ΔHAMD) and BSSI (ΔBSSI) after ECT treatment compared to baseline were calculated using the equations:

ΔHAMD=post−HAMD−pre−HAMD

ΔBSSI=post−BSSI−pre−BSSI

Alterations in ReHo (ΔReHo) and ALFF/fALFF (ΔALFF/fALFF) were calculated using the equations:

ΔReHo=post−ReHo−pre−ReHo

ΔALFF/fALFF=post−ALFF/fALFF−pre−ALFF/fALFF