Psychometric properties of the eight-item Morisky Medication Adherence Scale (MMAS-8) in a psychiatric outpatient setting.

The eight-item Morisky Medication Adherence Scale (MMAS-8) is a structured self-report measure of medication-taking behavior that has been widely used in various cultures. In Spain, no studies to date have analyzed the psychometric properties of the scale in psychiatric care. The purpose of the present instrumental study was to determine the psychometric properties of the Spanish version of the MMAS-8 in a sample of 967 consecutive psychiatric outpatients. The scale showed adequate construct validity and results pointed to a one-factor solution in which all the items contributed to the final index of adherence. The MMAS-8 exhibited significant correlation coefficients with the 10-item Drug Attitude Inventory, Form C of the Multidimensional Health Locus of Control scale, and the Hong Psychological Reactance Scale. Moreover, the MMAS-8 was able to differentiate between various mental disorder diagnosis groups. The findings of this study suggest that the Spanish version of the MMAS-8 is a reliable and valid measure of medication adherence that can be used in a psychiatric outpatient setting.