Objective: To validate the Autonomous and Controlled Motivation for Treatment Questionnaire (ACMTQ) for use in women with an eating disorder (ED).
Method: Data were available for 463 individuals. We assessed factor structure, internal reliability, test-retest reliability, convergent/divergent validity, and incremental predictive validity.
Results: Our data showed acceptable fit to our hypothesized model (comparative fit index = 0.92, root mean square error of approximation = 0.09, standardized root mean square residual = 0.09). We found test-retest reliability of 0.73 for both the autonomous (α = 0.85) and controlled (α = 0.80) subscales. Autonomous scores were more strongly associated with motivation measures (β = 0.37; 0.46) than with ED severity measures (β = -0.10; -0.18). Associations between autonomous motivation and symptom improvement over time supported predictive validity. Controlled motivation was associated with lower motivation (β = 0.02; -0.31) and with higher ED severity (β = 0.12; 0.47).
Conclusion: Our results suggest that the ACMTQ is valid for use in women with EDs and lend support to the validity of findings from previous ED studies that have used the ACMTQ.
Keywords: anorexia nervosa; bulimia nervosa; outpatient; psychometrics.
© 2018 John Wiley & Sons, Ltd and Eating Disorders Association.