Are patient beliefs important in determining adherence to treatment and outcome for depression? Development of the beliefs about depression questionnaire

BackgroundDepressive disorders are prevalent and costly but there is a lack of evidence on how to best select treatments for mild to moderate depression in primary care. Illness beliefs have been shown to influence the outcome from physical illness and our previous retrospective study suggested that beliefs may influence the duration of antidepressant medication. The development of a short questionnaire to measure beliefs will allow exploration of the relationship between beliefs, adherence to treatment and outcome for depression.MethodsA questionnaire was designed based on Leventhal's Common Sense Model of illness beliefs (CSM). Data from previous qualitative and quantitative studies as well as formal inventories were used to inform the content of individual items. The questionnaire was mailed to primary care patients with a recorded history of depression in the previous 2 years. Data were analysed by principal component analysis to determine underlying multidimensional structure and derive a shortened questionnaire.ResultsThree hundred and thirty-four respondents completed the questionnaire. Fifteen components (subscales) were derived which corresponded to aspects of the CSM dimensions for cause, control/cure, consequences and timeline. The identity dimension was retained as one subscale. Reliability coefficients determined the items which best represented each subscale; 52 items were retained to derive a new shortened questionnaire. Convergent construct validity was demonstrated by comparison with the generic brief illness perception questionnaire (BIPQ) and divergent construct validity was shown by comparison with the Hospital Anxiety and Depression scale (HADs).LimitationsThe study was adequately powered, but the response rate means that response bias cannot be excluded.ConclusionsBeliefs about depression are multi-faceted, but fit the dimensions of the CSM. The derived shortened questionnaire will be used to determine whether beliefs about depression are predictive of outcome in a future prospective study.