Objective: The Medication Adherence Rating Scale (MARS) is one of the most widely used measurements of adherence in schizophrenia (SZ). However, the data available regarding its psychometric properties are scarce. The aim of this study was to provide new data regarding the psychometric properties of the MARS in a multicenter community-dwelling sample of SZ patients.
Methods: This study was conducted in the French National network of the 10 FondaMental Expert Centers for SZ. The MARS was tested for construct validity, reliability, external validity and acceptability. In addition, data pertaining to sociodemographic information, clinical characteristics using the Positive and Negative Syndrome Scale (PANSS), the Scale to Assess Unawareness in Mental Disorder (SUMD), the Calgary Depression Scale for Schizophrenia (CDRS) and therapeutic adherence using the Brief Adherence Rating Scale (BARS) were collected.
Results: Three hundred and nineteen patients were included. The 3-factor structure of the MARS was confirmed using confirmatory factor analysis: RMSEA=0.05, CFI=0.95, and WRMR=0.88. The unidimensionality of each factor was supported by the satisfactory INFIT statistics. Item internal consistencies were all higher than 0.15 and the Kuder-Richardson were close to 0.6, except for factor 2, which was close to 0.5. Significant associations with BARS, PANSS, CDRS showed satisfactory external validity. The acceptability was excellent as all patients complete the MARS, without missing values.
Conclusion: The MARS is a short self-administered instrument with acceptable psychometric properties that yields important information about adherence to pharmacological treatment. Some improvements might be considered to enhance its validity and reliability.
Keywords: Antipsychotics; Medication adherence; Psychosis; Schizophrenia.
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