Development and validation of the General Attitude towards Medication Questionnaire (GAMQ)

Objective: Attitudes towards medication can affect treatment outcomes and adherence through mechanisms such as placebo and nocebo effects. Questionnaires assessing both negative and positive attitudes towards medication in general are however lacking. To fill this gap, we developed and validated the General Attitude towards Medication Questionnaire (GAMQ). Methods: Items were selected and adapted from existing questionnaires by a group of experts. Validation of the original Dutch version took place in 4 samples: 2 recruited from the general population and 2 patient samples. We evaluated the psychometric properties of the GAMQ by determining the factor structure and its stability across samples, internal consistency, and convergent validity. Results: The GAMQ contains 6 positive and 6 negatively worded items. A factor structure was observed with three subscales, representing ‘Trust in medication’, ‘Concerns about medication’, and ‘Reluctance to use medication’. The fit of the factor structure was satisfactory across samples with an adequate or close to adequate fit. The total scale showed good internal consistency, convergent, and concurrent validity. Conclusion: The newly developed GAMQ showed satisfactory psychometric properties in a variety of populations. The GAMQ is the first scale to assess both positive and negative attitudes towards medication in general and might be an informative measure for predicting treatment outcomes, adherence, as well as placebo and nocebo effects.