Fig. 4.

Mediation analysis of longitudinal changes of neurometabolites concentrations, FCS, and PANSS symptom scores in the FEP patients. (A) The association between the changes of GABA concentration in the MPFC and the recovery of PANSS positive symptom score was mediated by the FCS between MPFC and DMN. (B) The association between the changes of NAA concentration in the MPFC and the recovery of PANSS positive symptom score was mediated by the FCS between PCC/PCu and DMN. Standardized path coefficients are labeled along each path. The path a refers to the effect of neurometabolic concentration on DMN FCS; the path b refers to the effect of DMN FCS on PANSS symptom scores, controlling for neurometabolic level; indirect effect (product a*b) refers to the amount of mediation that the FCS of DMN had on the neurometabolic concentration – PANSS symptom relationship. $\mathrm{\Delta }$ denotes the changes before and after treatment. Abbreviations: FCS, functional connectivity strength; PANSS, Positive and Negative Syndrome Scale; FEP, first-episode psychosis patients; MPFC, medial prefrontal cortex; PCC/PCu, posterior cingulate cortex/precuneus; GABA, gamma-aminobutyric acid; NAA, N-acetyl-aspartate. * p < 0.05, ** p < 0.01.