Measures of visual hallucinations: Review and recommendations.

BACKGROUND: Studies designed to investigate visual hallucinations (VH) require reliable and valid measures that can appropriately capture peoples' experiences. This review aimed to assess the psychometric rigour and usefulness of VH measures. METHOD: A systematic literature search was carried out against inclusion criteria (e.g. more than one specific question on VH, measures for adults in clinical and non-clinical populations). Eighteen measures were identified and rated against an adapted evaluation grid, which included essential criteria such as clear purpose and definition, psychometric properties including reliability and validity, and appropriate exploration of visual hallucinations. RESULTS: Measures could be categorised into 3 groups; those for general psychotic symptoms, those for all hallucinations, or those specifically for visual hallucinations. With one exception (the North East Visual Hallucinations Inventory), the measures were considered to be limited as they often targeted one population and hence lacked generalisability, or were limited in the characteristics of the visions that were described, or that psychometric properties were not adequately evaluated. CONCLUSIONS: Measures of VH require further development. The need to establish a clearer definition of VH is essential to provide clarity and consistency within research and practice. Measures need to demonstrate good psychometric properties to indicate robustness whilst being sensitive to change to help in the evaluation of treatments. Other recommendations include developing cross-cultural measures and involving service users in item development.