Assessment of motivation in schizophrenia: Patient- and clinician-rated outcomes

Negative symptoms, such as apathy and diminished motivation, are critical for prognosis and treatment outcomes in neurological and psychiatric disorders. However, constructs and assessment scales differ significantly across neuropsychiatric disorders. This study examines the psychometric properties of two scales used to assess apathy - the apathy-motivation index (AMI) and the diagnostic criteria for apathy (DCA) - compared to schizophrenia-specific tools, namely the brief negative symptoms scale (BNSS) and the positive and negative syndrome scale (PANSS).

We conducted a cross-sectional, multicenter study with 151 individuals with schizophrenia across six European sites. Participants were assessed using the AMI, DCA, BNSS, PANSS, and other clinical and functional scales. BNSS motivation and pleasure factor (BNSS_MAP) assessed motivation, and personal and social performance (PSP) assessed functioning. Convergent validity across these tools was examined through bivariate correlations (Pearson r) and exploratory factor analysis for the AMI. Cut-off points for apathy used receiver operating characteristic (ROC) analysis, with DCA as the reference.

We found low convergence between BNSS_MAP and AMI (r=.31, p<.001) and moderate convergence between BNSS_MAP and DCA (r=.48, p<.001). PSP correlated with BNSS_MAP, PANSS_negative and DCA (r=-.615, r=-.446 and r=-.430, respectively, all p<0.001), but not with AMI (r=-.108; p=.218). ROC analysis yielded cut-off points of 28.5 (BNSS total), 16.5 (BNSS_MAP), 14.5 (PANSS_negative), and 33.5 (AMI total) for detecting clinical apathy.

Current apathy and motivation scales show limited overlap, reflecting the complexity of measuring transdiagnostic constructs. Combining clinician- and patient-rated measures may provide a more comprehensive understanding of apathy in schizophrenia and other neuropsychiatric conditions.