Introduction

Schizophrenia is a severe and disabling mental disorder that imposes extensive physical, psychological, and social burdens, profoundly affecting quality of life (QoL).1, 2, 3 Subjective QoL may also be influenced by emotional processing deficits, alexithymia, and patients’ perceived treatment experiences, which are important considerations when interpreting patient-reported outcomes in schizophrenia.4 Measuring QoL provides insights beyond clinical symptoms, helping clinicians and researchers identify intervention targets, evaluate treatment effects, and understand determinants of well-being.5

The Schizophrenia Quality of Life questionnaire (S-QoL41) is a schizophrenia-specific patient-reported outcome measure (PROM) developed from patients’ perspectives to assess quality of life and recovery-related outcomes in schizophrenia.1 A shortened version (S-QoL18) was subsequently developed to reduce respondent burden,2 and a computerized adaptive version (S-QoL-MCAT) was introduced to improve assessment efficiency while maintaining precision.6 These instruments are used to support treatment evaluation, outcome monitoring, and patient-centred care.1,2

Despite their widespread use in people with schizophrenia, including those with severe cognitive impairments, homeless individuals, and inpatients, and their availability in multiple languages,1,2,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 no systematic review has comprehensively evaluated the psychometric properties of the S-QoL41, S-QoL18, and S-QoL-MCAT instruments. Although derived from the same conceptual framework, differences in instrument length and administration format may affect their psychometric performance and clinical utility, necessitating a comprehensive evaluation of their measurement properties to inform instrument selection. Using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) methodology, an internationally recognised framework for evaluating PROMs alongside its Risk of Bias Checklist, we provide a standardised assessment of these instruments. To our knowledge, this is the first comprehensive evaluation of all three S-QoL instruments. Neurobiological findings are additionally discussed as complementary contextual evidence to aid interpretation of the clinical and theoretical relevance of the constructs assessed by these instruments. Outside the scope of COSMIN appraisal, these findings are considered exploratory and hypothesis-generating rather than evidence of construct validity, with potential relevance for future mechanistic research. By synthesising evidence on validity, reliability, responsiveness, and interpretability, this review identifies the strengths and limitations of each instrument and informs the selection of robust, person-centred measures of QoL for both clinical practice and research.