A transdiagnostic approach of negative symptoms in psychiatric disorders: replication of a two-factor structure in major depressive disorder and bipolar disorder

Recent empirical findings suggest that negative symptoms are not limited to schizophrenia (SCZ) but also present in major depressive disorder (MDD) and bipolar disorder (BD) patients. Although SCZ patients generally showed a latent structure comprising the motivation and pleasure (MAP) and expression (EXP) factors, it remains unclear whether the same latent structure exists in MDD and BD patients. We administered the Clinical Assessment Interview for Negative Symptoms (CAINS) and the Brief Negative Symptom Scale (BNSS) to 179 MDD patients and 152 BD patients. Confirmatory Factor Analysis (CFA) was conducted to examine the one-factor model, the two-factor model of the MAP and the EXP domain, the five-factor model of anhedonia, avolition, asociality, alogia, and blunted affect, and the hierarchical model comprising the first-order five-factor, and the second-order two-factor (MAP and EXP factors). We further examined the correlations between demographics and the negative symptom dimensions found in the best factor model. The CFA showed that, when the CAINS and the BNSS were combined together, the two-factor model of MAP and EXP provided the best model fit than other competing models, in the MDD alone sample, BD alone sample, and the combined clinical sample. The two-factor model of the MAP and EXP appears to be a stable, transdiagnostic latent structure of negative symptoms across BD and MDD. Clarifying negative symptoms in MDD and BD can facilitate future research on the underlying neural mechanisms of the MAP and EXP dimensions.