Psychometric Properties of the 8-Item Reflective Functioning Questionnaire (RFQ-8) in Nigerian Clinical and Non-Clinical Populations

Background: Mentalization refers to the ability to comprehend and appreciate the mental states of self and others. Deficits in mentalization, particularly hypomentalization, have been observed to be strongly linked to schizophrenia spectrum disorders. The 8-item Reflective Functioning Questionnaire (RFQ-8) is a brief instrument commonly used to measure hypomentalization, but it has not been validated in Nigeria. This study aimed to determine the psychometric properties of the RFQ-8, scored unidimensionally to measure hypomentalization, among Nigerian clinical and non-clinical populations. Methods: A cross-sectional study was carried out in Lagos with 159 participants (53 patients with first episode psychosis (FEP), 53 first-degree relatives, and 53 healthy controls). Data were collected using the RFQ-8, Difficulties in Emotion Regulation Scale–Short Form (DERS-SF), and Brief Psychiatric Rating Scale (BPRS). Reliability, convergent and divergent validity, and exploratory factor analysis were examined. Results: The RFQ-8 showed good internal consistency (Cronbach’s α = 0.901). Its convergent validity was supported by a strong positive correlation with the DERS-SF (r = 0.720, p < 0.001). A weak non-significant correlation with BPRS scores (r = 0.095, p = 0.499) suggested divergent validity. Exploratory factor analysis supported a unidimensional structure (KMO = 0.964, Bartlett’s χ² = 2773.152, p < 0.001), with a single factor accounting for 94.6% of the variance. Conclusion: The RFQ-8 is a reliable and valid instrument for assessing mentalization deficit in Nigerian populations, including patients with FEP. Its brevity and impressive psychometric properties make it appropriate for use in clinical practice and research.