Assessment of decisional capacity. A systematic review and analysis of instruments regarding their applicability to requests for assisted suicide.

Background: Decisional capacity is an important requirement for assisted suicide, which has been legalized in an increasing number of countries. While several instruments have been developed over the past few decades to assess the capacity to consent to treatment, little is known about their applicability to assessing capacity in the context of requests for assisted suicide.

Methods: Systematic review of instruments assessing decisional capacity published up to March 2024. Data concerning criteria for determining decisional capacity, psychometric properties, and other aspects were extracted from all instruments included. Selected instruments were analyzed regarding their applicability to requests for assisted suicide.

Results: We identified 23 instruments assessing the capacity to consent to treatment. There is considerable heterogeneity regarding the criteria utilized for assessing decisional capacity and their operationalization. Next to more cognitive abilities, some instruments directly incorporated emotions and values. Five instruments were assessed for applicability to requests for assisted suicide. The framing of decisional capacity within the context of disease and treatment options frequently limits the application of instruments to assess decisional capacity in the context of requests for assisted suicide.

Conclusions: No instrument could be identified that could be applied to assessing decisional capacity in the context of requests for assisted suicide without any limitations or without necessitating adjustments. Further normative and empirical work is required for developing an instrument that could be applicable in this context.