Schizophr Res. 2008;100( 1-3):53-9.
Adherence to medication is an important predictor of illness course and outcome in
psychosis. The Medication Adherence Rating Scale (MARS) is a ten-item self-report
measure of medication adherence in psychosis [Thompson, K., Kulkarni, J., Sergejew,
A.A., 2000. Reliability and validity of a new Medication Adherence Rating Scale (MARS)
for the psychoses. Schizophrenia Research. 42. 241-247]. Although initial results
suggested that the scale has good reliability and validity, the development sample
was small. The current study aimed to establish the psychometric properties of the
MARS in a sample over four times larger. The scale was administered to 277 individuals
with psychosis, along with measures of insight and psychopathology. Medication adherence
was independently rated by each individual's keyworker. Results showed the internal
consistency of the MARS to be lower than in the original sample, though adequate.
MARS total score correlated weakly with keyworker-rated adherence, hence concurrent
validity of the scale appeared only moderate to weak. The three factor structure of
the MARS was replicated. Examination of the factor scores suggested that the factor
1 total score, which corresponds to the Medication Adherence Questionnaire [Morisky,D.E.,
Green,L.W. and Levine,D.M., 1986. Concurrent and predictive validity of a self-reported
measure of medication adherence. Medical Care. 24, 67-74] may be a preferable measure
of medication adherence behaviour to the total scale score.