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

Published online by Cambridge University Press:  08 July 2025

Leonie Kupsch ,
Jakov Gather Open the ORCID record for Jakov Gather [Opens in a new window] ,
Jochen Vollmann ,
Stephan Nadolny Open the ORCID record for Stephan Nadolny [Opens in a new window]  and
Jan Schildmann Open the ORCID record for Jan Schildmann [Opens in a new window]
Leonie Kupsch*
Affiliation:
Institute for History and Ethics of Medicine, Interdisciplinary Centre for Health Sciences, Medical Faculty of Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
Jakov Gather
Affiliation:
Institute for Medical Ethics and History of Medicine, Ruhr University Bochum, Bochum, Germany Department of Psychiatry, Psychotherapy and Preventive Medicine, LWL University Hospital, Ruhr University Bochum, Bochum, Germany
Jochen Vollmann
Affiliation:
Institute for Medical Ethics and History of Medicine, Ruhr University Bochum, Bochum, Germany
Stephan Nadolny
Affiliation:
Institute for History and Ethics of Medicine, Interdisciplinary Centre for Health Sciences, Medical Faculty of Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
Jan Schildmann
Affiliation:
Institute for History and Ethics of Medicine, Interdisciplinary Centre for Health Sciences, Medical Faculty of Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
*
Corresponding author: Leonie Kupsch; Email: leonie.kupsch@uk-halle.de

Abstract

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.

Keywords

assisted suicidedecisional capacityinstrumentssystematic review

Information

Type
Review/Meta-analysis
Information
European Psychiatry , Volume 68 , Issue 1 , 2025 , e91
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of European Psychiatric Association

Introduction

Assisted suicide refers to assisting a person in ending their own life, with the final action being carried out by the person themselves. This practice has been legalized in an increasing number of countries [Reference Mroz, Dierickx, Deliens, Cohen and Chambaere1, Reference Güth, Weitkunat, McMillan, Schneeberger and Battegay2]. Decisional capacity is an important requirement for legally and ethically justified assisted suicide [Reference Shaw, Trachsel and Elger3–Reference Hachtel, Häring, Kochuparackal, Graf and Vogel6]. If a person is of legal age, they are generally assumed to have decisional capacity for decision-making situations regarding medical treatment. A formal assessment of decisional capacity should be conducted for a specific situation and context only if there are any reasons for doubts [Reference Grisso and Appelbaum7–Reference Genske9]. By contrast, a proactive formal assessment of decisional capacity or a reliable elimination of aspects that could impair decisional capacity is often called for in the context of requests for assisted suicide [Reference Ganzini, Leong, Fenn, Silva and Weinstock10–Reference Saß and Cording13].

Different terms including “capacity,” “competence,” and “competency” are mentioned when referring to decisional capacity, which is partly due to linguistic or conceptual differences. For this article, these terms were subsumed under “decisional capacity.” A widely used definition of decisional capacity includes four abilities as outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7, Reference Scholten and Haberstroh14]:

  1. 1. The ability to understand information relevant to the decision at hand (understanding)

  2. 2. The ability to apply relevant information to one’s own situation in the sense of acknowledging one’s illness and treatment options (appreciation)

  3. 3. The ability to weigh and evaluate options regarding possible consequences in a logically consistent way (reasoning)

  4. 4. The ability to evidence a choice

Some authors have criticized this definition of decisional capacity and its focus on cognitive abilities as insufficient. They call particularly for the inclusion of values, emotions, and social aspects to ascertain decisional capacity [Reference Hawkins and Charland8, Reference Hermann, Trachsel, Elger and Biller-Andorno15].

Empirical studies indicate that in practice, many clinicians do not refer to standardized procedures or specifications but rather take an individual approach to assessing decisional capacity [Reference Schweitser, Stuy, Distelmans and Rigo4, Reference Wiebe, Kelly, McMorrow, Tremblay-Huet and Hennawy5, Reference Krug, Gerhards, Bittner, Scorna, Kaufner and Kokott16]. This can lead to heterogenous results depending on the clinician doing the assessment [Reference Appelbaum17]. Furthermore, the personal values of clinicians could potentially influence capacity assessment [Reference Ganzini, Leong, Fenn, Silva and Weinstock10, Reference Hermann, Trachsel and Biller-Andorno18]. Against this background, establishing a procedure with predefined criteria could help to support the process of assessing decisional capacity. This seems particularly needed in far-reaching decisions, such as in the context of requests for assisted suicide.

A number of instruments assessing capacity to consent to treatment have been developed in the past few decades [Reference Amaral, Afonso, Simões and Freitas19–Reference Lamont, Jeon and Chiarella23]. However, little is known about their applicability to assessing decisional capacity in cases of requests for assisted suicide, as these cases do not necessarily constitute a medical decision-making situation. The aim of this paper is, firstly, to present and appraise published instruments assessing capacity to consent to treatment based on a systematic literature review. Secondly, all instruments assessing decisional capacity by including all four abilities outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7] and in relation to a specific decision were analyzed regarding their applicability to requests for assisted suicide.

Methods

Systematic review

Based on a recent systematic review by Amaral et al. [Reference Amaral, Afonso, Simões and Freitas19] on instruments assessing capacity to consent to treatment published up to 2018, we conducted a search for instruments published since 2018 in relevant databases (MEDLINE [Ovid], Web of Science, PsycINFO, CINAHL, Cochrane Central Register of Controlled Trials [CENTRAL]) using a modified search strategy on October 1, 2022, and again on March 15, 2024. Search strategies and respective results are documented in Appendix 1 (Supplemental material 1).

Criteria for inclusion and exclusion of articles were modeled on the approach of Amaral et al. [Reference Amaral, Afonso, Simões and Freitas19]: Instruments assessing capacity to consent to treatment were included, while those assessing capacity to consent to research, create advance directives, or for non-medical decisions were excluded. Furthermore, all instruments assessing decisional capacity in children and adolescents, guidelines on decisional capacity, and instruments without specifications for practical application were also excluded.

After removing any duplicates, the initial search yielded 3628 articles that were then imported onto the platform Rayyan [Reference Ouzzani, Hammady, Fedorowicz and Elmagarmid24]. During the search update, 1056 additional articles published since October 2022 were identified. The titles and abstracts of all 4684 articles were screened and assessed independently by two researchers utilizing the predefined criteria. Potentially relevant articles identified in this way were included or excluded based on their full text. Figure 1 documents the search and the screening process using the PRISMA 2020 flowchart [Reference Page, McKenzie, Bossuyt, Boutron, Hoffmann and Mulrow25].

Figure 1.

PRISMA 2020 flowchart.

Due to limited resources and the small number of newly included articles, no quality appraisal was performed. Data on various characteristics of the instruments were extracted from all articles identified by Amaral et al. [Reference Amaral, Afonso, Simões and Freitas19] as well as from all newly included publications and summarized in Table 1.

Table 1.

Overview of instruments assessing capacity to consent to treatment

Structured analysis of the potential applicability of assessment instruments to requests for assisted suicide

After extracting any descriptive data, instruments were analyzed regarding their applicability in practice to requests for assisted suicide. We defined two inclusion criteria for this structured analysis: First, instruments should assess all four abilities outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7], as they are widely regarded to be relevant for assessing decisional capacity [Reference Hawkins and Charland8, Reference Genske9]. Second, only instruments that can be used for assessing capacity for the decision at hand were included, as decisional capacity is generally interpreted as a context-specific ability [Reference Grisso and Appelbaum7–Reference Genske9]. Furthermore, the current and individual situation of the person making the request should be taken into account, particularly regarding the assessment of decisional capacity in the context of requests for assisted suicide.

All instruments fulfilling both inclusion criteria were then analyzed regarding their applicability to requests for assisted suicide using four questions that are relevant in the context of the normative and legal requirements for assessing decisional capacity in cases of requests for assisted suicide:

  1. 1. For which specific context was the instrument designed? Is a decision-making situation regarding treatment options a premise of the instrument, or is it possible to assess decisional capacity if there are no treatment options or even in the absence of an underlying illness?

  2. 2. Is the scope of application of the assessment instrument limited to a specific illness or group of people, or can it be applied to different situations and groups of people?

  3. 3. Does the instrument assess other aspects (e.g. values or emotions) in addition to the four abilities outlined by Grisso and Appelbaum?

  4. 4. Does the instrument include information about the assessors, for example, regarding reasons that could potentially influence or distort the assessment of decisional capacity?

The first two questions are based on the fact that reasons and motives for requesting assisted suicide can differ, and not every country allowing assisted suicide requires requestors to have some kind of underlying illness [Reference Mroz, Dierickx, Deliens, Cohen and Chambaere1, Reference Saß and Cording13]. As there is also a call for the inclusion of, for example, values and emotions to determine their possible impact on a person’s decisional capacity [Reference Hawkins and Charland8, Reference Hermann, Trachsel, Elger and Biller-Andorno15], the third question analyzes whether aspects other than the four abilities are assessed. Lastly, the fourth question is based on studies showing that personal values and attitudes of the assessor regarding assisted suicide could possibly influence requirements and thresholds for decisional capacity [Reference Ganzini, Leong, Fenn, Silva and Weinstock10, Reference Hermann, Trachsel, Elger and Biller-Andorno15]. All four questions were developed for analyzing the assessment instruments regarding their applicability to requests for assisted suicide, but are not intended as set requirements.

Results

We identified a total of 23 instruments assessing the capacity to consent to treatment. In addition to the 17 instruments [Reference Grisso and Appelbaum7, Reference Scholten and Haberstroh14, Reference Etchells, Darzins, Silberfeld, Singer, McKenny and Naglie26–Reference Cea and Fisher29, Reference Carney, Neugroschl, Morrison, Marin and Siu31–Reference Bean, Nishisato, Rector and Glancy34, Reference Wong, Clare, Holland, Watson and Gunn36, Reference Fitten and Waite37, Reference Edelstein40–Reference Grisso and Appelbaum44, Reference Tomoda, Yasumiya, Sumiyama, Tsukada, Hayakawa and Matsubara48, Reference Roth, Lidz, Meisel, Soloff, Kaufman, Spiker and Foster49, Reference Schmand, Gouwenberg, Smit and Jonker53–Reference Vellinga, Smit, van Leeuwen, van Tilburg and Jonker55] Amaral et al. [Reference Amaral, Afonso, Simões and Freitas19] had already found in the course of their review, 6 new instruments published since 2018 and reported in nine publications [Reference Carney, Emmert and Keefer30, Reference Kumar, Berry, Koning, Rossell, Jain and Elkington35, Reference Moynihan, O’Reilly, O’Connor and Kennedy38, Reference Chang and Bourgeois39, Reference Jayes, Palmer and Enderby45–Reference Jayes, Austin and Brown47, Reference Hermann, Feuz, Trachsel and Biller-Andorno50, Reference Trachsel and Biller-Andorno52] were identified.

An overview of data extracted regarding the format of the instruments, abilities assessed by the instruments, duration of use, scoring procedures and cut-off scores, psychometric properties, and pilot study populations can be found in Table 1.

When comparing the various instruments, similarly to the general discussion, different terms are mentioned when referring to decisional capacity. In light of the core conceptual and empirical similarities between the instruments, only the term “decisional capacity” is used throughout this article, though it should be noted that the instruments primarily assess the abilities that are considered to be required for decisional capacity. Regarding the majority of instruments, their conceptualization of decisional capacity is based on the four abilities outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7]. However, there are different approaches to operationalizing these abilities.

Operationalization of understanding, appreciation, reasoning, and evidencing a choice

Regarding understanding, instruments usually assess whether a person is able to comprehend information related to their illness, possible treatment options, and risks and benefits. Some instruments also include further aspects, such as determining whether the person being assessed understands that they can refuse the proposed treatment options [Reference Etchells, Darzins, Silberfeld, Singer, McKenny and Naglie26, Reference Roth, Lidz, Meisel, Soloff, Kaufman, Spiker and Foster49], what the purpose or objective of the treatment is [Reference Kumar, Berry, Koning, Rossell, Jain and Elkington35–Reference Fitten and Waite37], or what risks and benefits may result from refusing treatment [Reference Wong, Clare, Holland, Watson and Gunn36, Reference Tomoda, Yasumiya, Sumiyama, Tsukada, Hayakawa and Matsubara48, Reference Hermann, Feuz, Trachsel and Biller-Andorno50].

There are two different methods being primarily used to operationalize appreciation: Some of the instruments assess appreciation as the acknowledgement of illness and possible treatment options [Reference Grisso and Appelbaum7, Reference Moynihan, O’Reilly, O’Connor and Kennedy38–Reference Edelstein40, Reference Appelbaum and Grisso42–Reference Grisso and Appelbaum44]. Other instruments determine whether the potential consequences of a decision can be anticipated [Reference Etchells, Darzins, Silberfeld, Singer, McKenny and Naglie26, Reference Cea and Fisher29, Reference Marson, Ingram, Cody and Harrell32, Reference Schmand, Gouwenberg, Smit and Jonker53]. Several instruments [Reference Moye, Karel, Edelstein, Hicken, Armesto and Gurrera28, Reference Carney, Emmert and Keefer30, Reference Bean, Nishisato, Rector and Glancy34, Reference Hermann, Feuz, Trachsel and Biller-Andorno50, Reference Vellinga, Smit, van Leeuwen, van Tilburg and Jonker54] utilize both methods. Another aspect that is sometimes included in the assessment of appreciation is a possible distrust of medical staff [Reference Moye, Karel, Edelstein, Hicken, Armesto and Gurrera28, Reference Bean, Nishisato, Rector and Glancy34].

Reasoning is defined as the ability to manipulate information rationally by comparing, weighing, and evaluating options logically and consistently, especially concerning possible consequences and effects on one’s own life situation, which is operationalized in this way by some instruments [Reference Grisso and Appelbaum7, Reference Carney, Neugroschl, Morrison, Marin and Siu31, Reference Chang and Bourgeois39, Reference Appelbaum and Grisso42–Reference Grisso and Appelbaum44, Reference Vellinga, Smit, van Leeuwen, van Tilburg and Jonker54]. Other instruments focus on weighing risks and benefits [Reference Moye, Karel, Edelstein, Hicken, Armesto and Gurrera28, Reference Cea and Fisher29] or relevant information in general [Reference Jayes, Palmer and Enderby46, Reference Hermann, Feuz, Trachsel and Biller-Andorno50]. The logically consistent justification of the decision [Reference Carney, Emmert and Keefer30, Reference Marson, Ingram, Cody and Harrell32, Reference Bean, Nishisato, Rector and Glancy34, Reference Hermann, Feuz, Trachsel and Biller-Andorno50, Reference Schmand, Gouwenberg, Smit and Jonker53] is an important aspect of the assessment of reasoning for some instruments.

Assessing the ability to evidence a choice includes a direct question about the final decision of the person being assessed for the majority of the instruments characterized. In some cases, it should also be documented whether the person would like to make the decision themselves or rather have someone else decide for them [Reference Bean, Nishisato, Rector and Glancy34, Reference Tomoda, Yasumiya, Sumiyama, Tsukada, Hayakawa and Matsubara48]. One instrument also emphasizes aspects such as communication and orientation as part of the assessment [Reference Carney, Neugroschl, Morrison, Marin and Siu31].

Possible applicability in the context of requests for assisted suicide

Applying the inclusion criteria outlined under 2.2, six instruments [Reference Grisso and Appelbaum7, Reference Moye, Karel, Edelstein, Hicken, Armesto and Gurrera28, Reference Carney, Emmert and Keefer30, Reference Bean, Nishisato, Rector and Glancy34, Reference Moynihan, O’Reilly, O’Connor and Kennedy38, Reference Hermann, Feuz, Trachsel and Biller-Andorno50] were analyzed regarding their possible applicability to assessing decisional capacity in the context of requests for assisted suicide, utilizing the four questions for structured analysis.

The results of the analysis for five of the six instruments are described below. An analysis of the Dundrum Capacity Ladders [Reference Moynihan, O’Reilly, O’Connor and Kennedy38] was not possible as the instrument was not available during research or after contacting the authors.

Assessment of Capacity to Consent to Treatment (ACCT [Reference Moye, Karel, Edelstein, Hicken, Armesto and Gurrera28])

The ACCT is based on the premise that the person being assessed has an illness and has to make a decision regarding treatment options, which is why, for example, for assessing understanding, information about the illness is provided followed by questions checking a person’s comprehension of their “medical problem” [Reference Moye, Karel, Edelstein, Hicken, Armesto and Gurrera28]. For the same reason, all questions aim at assessing the capacity to consent to treatment specifically. In order to assess whether a person acknowledges potential treatment options, for instance, they are asked, inter alia, if there are any doubts about the possible effectiveness of the proposed treatment or concerns about the doctors’ intentions. The assessors are given specific questions by the ACCT, but these can be flexibly adapted to a variety of situations. A special feature is the additional assessment of social aspects and values, including visual aids. Information on assessors, on the other hand, is not included.

Bedside Capacity Assessment Tool (BCAT [Reference Carney, Emmert and Keefer30])

The BCAT was also designed with a decision-making situation regarding treatment options in mind, which is why, for understanding, a person’s knowledge about their treatment choices or about their medical decision-making situation in general is assessed. The instrument is also based on the assumption that a person has an underlying illness. The wording of questions for assessing decisional capacity is not specified. Instead, different aspects required for decisional capacity are listed. Overall, the BCAT can be used for a wide range of clinical situations. It should be noted though that, according to the authors of the BCAT, the instrument is not intended for use in more complex cases. Assessors should check whether the reasons delineated are consistent with values held by the person being assessed. Information relating to the assessors is not included.

Competency Interview Schedule (CIS [Reference Bean, Nishisato, Rector and Glancy34])

The CIS was created as a structured interview for patients with a psychiatric illness and an indication for electroconvulsive therapy. This is also reflected by the questions, for which specific wording is provided, and explicitly tests the decisional capacity for this intervention. Accordingly, there are limitations regarding the application for assessing decisional capacity for assisted suicide, as evidenced, for example, by the questions on whether the person believes that the medical staff expect them to remain in hospital or if the person wants the decision to be made by someone else. In addition to the four abilities outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7], various other aspects are assessed, such as whether a person feels pressured or coerced into making a decision. Information on assessors is not part of the assessment.

MacArthur Competence Assessment Tool – Treatment (MacCAT-T [Reference Grisso and Appelbaum7, Reference Scholten and Haberstroh14, Reference Grisso, Appelbaum and Hill-Fotouhi41])

The MacCAT-T is also based on the premise that the person being assessed is affected by an illness and has to make a decision regarding treatment options. Examples include questions on acknowledging their illness or treatment options for assessing appreciation, or their comprehension of these treatment options, for which they should recount their own understanding of the treatment suggested. The MacCAT-T has already been used to assess decisional capacity for various groups of people [Reference Kolva, Rosenfeld and Saracino56, Reference Ladwig, Pauls, Gerke, Trachsel and Nestoriuc57], and the questions can, therefore, be flexibly adapted to many situations. Translations into different languages are available. Aspects other than the four abilities outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7] and information on the assessors are not included.

Urteilsfähigkeit-Dokument (U-Doc [Reference Hermann, Feuz, Trachsel and Biller-Andorno50–Reference Trachsel and Biller-Andorno52])

The U-Doc was developed to assess decisional capacity in the context of the legal framework in Switzerland. While there are some terminological and conceptual differences due to this framework, all four abilities are incorporated into the instrument. Similar to the other instruments, a decision-making situation regarding treatment options is also a premise for the U-Doc. The latter form contains both suggested wording for questions and explanations of the abilities required for decisional capacity. Overall, the wording can be flexibly adapted to the situation at hand as necessary. As with the instruments discussed previously, the applicability to assessing decisional capacity for people with no underlying illness or suggested treatment options is limited, as the U-Doc mainly assesses appreciation as an acknowledgement of illness and treatment options, but it is possible to directly adapt some of the items to non-medical decision-making situations. In addition to the four abilities, the U-Doc also directly assesses other aspects, such as values, biographical factors and emotions, and the possible influence of internal and external pressure on decision-making. Furthermore, the form (which needs to be distinguished from the underlying concept) also includes a reminder that assessors should critically examine their judgment and reflect on their own bias regarding personal values and conflicts of interest.

Table 2 provides an overview of the structured analysis of the instruments using the predefined criteria.

Table 2.

Structured analysis of the possible applicability of instruments assessing decisional capacity to requests for assisted suicide

Discussion

The main findings of our review are, on the one hand, the existence of a large number of instruments for assessing capacity to consent to treatment which are heterogeneous in several respects, including the operationalization of established criteria for decisional capacity. On the other hand, 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. Whether these limitations are relevant for the conceptualization of decisional capacity the instruments are based on itself or whether applying these instruments to requests for assisted suicide would only necessitate adjusting items to this specific context – similarly to specific decision-making situations about treatment – remains open for discussion. For the most part, the instruments identified show deficits regarding psychometric properties and quality. Data on interrater reliability is reported for most instruments, but there is often a lack of further information on the reliability of these instruments. Additionally, given the known challenges when conceptualizing what constitutes a gold standard for validating instruments assessing decisional capacity, in order to test the validity, the assessment done using the instrument was often compared with the judgment of experts [Reference Sturman20] or established instruments, such as the Mini-Mental State Examination (MMSE). Comparison with the MMSE has been criticized [Reference Dunn, Nowrangi, Palmer, Jeste and Saks21, Reference Moye, Gurrera, Karel, Edelstein and O’Connell22] as it is not suitable for the assessment of decisional capacity [Reference Lamont, Jeon and Chiarella23, Reference Álvarez Marrodán, Baón Pérez, Navío Acosta, Verdura Vizcaino, Cantón Álvarez and Ventura Faci58].

When comparing the instruments, it should be noted that different terms such as “capacity,” “competence” or “competency” are mentioned. This does not necessarily imply different underlying concepts as it could be due to linguistic differences. However, legislation on decisional capacity – and thus its conceptualization – varies between different countries, which could be reflected in the terminology. Despite these potential differences, the majority of the instruments are based on the four abilities model [Reference Grisso and Appelbaum7]. However, the approach to operationalizing these four abilities can differ considerably. Distinguishing whether the different ways of operationalizing abilities affect the conceptualization of decisional capacity itself or can rather be seen as heterogenous interpretations of the concept went beyond this project. Other differences between the instruments relate to an extension of the concept of decisional capacity beyond the four abilities to include, for example, values or emotions as a separate part of the assessment, as is the case with the U-Doc. These and other extensions regarding the conceptualization and operationalization of decisional capacity take into account the criticism of a more cognitive-oriented capacity assessment [Reference Hawkins and Charland8, Reference Hermann, Trachsel, Elger and Biller-Andorno15].

Another reason for the heterogeneity of the instruments is the assessment of aspects that relate to the process of testing decisional capacity. A notable example is the reference to factors that could have an influence on the capacity judgment of the assessors by the U-Doc form. In view of empirical data on the potential impact of individual moral values on the assessment of decisional capacity [Reference Ganzini, Leong, Fenn, Silva and Weinstock10, Reference Hermann, Trachsel and Biller-Andorno18], the disclosure of such factors could be a useful impetus for the assessors’ reflection process.

Regarding the assessment of decisional capacity in the context of requests for assisted suicide, when analyzing the items, we were unable to find an instrument during our research that could be directly applied to this situation. Six instruments fulfilled the inclusion criteria for further analysis since they assess all four abilities outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7] and can be applied to the decision at hand. All five instruments that could be analyzed are based on the premise that the person being assessed has to make a decision regarding treatment options; however, items of both the U-Doc and the BCAT can be adapted to other healthcare decision-making situations and, in the case of the U-Doc, also to situations in which no illness is present. Requests for assisted suicide are not always made in the context of an illness, but can also be made, for example, by elderly people who do not wish to continue living [Reference Spittler59, Reference Bartsch, Landolt, Ristic, Reisch and Ajdacic-Gross60]. Since assisted suicide is legal in some countries even in the absence of illness, the remaining instruments are currently not applicable for such situations.

Furthermore, it remains unclear which kind of requirements should be set for decisional capacity in the context of assisted suicide, including whether there could be other approaches to operationalizing decisional capacity and whether these requirements could be similar to those for decision-making situations regarding treatment options as requests for assisted suicide differ from established medical decision-making situations. Against the background of interpretations of decisional capacity as a relational ability according to which requirements for decisional capacity should be adapted relative to the risks associated with a decision [Reference Vollmann61, Reference Kim and Berens62], it thus also remains unclear whether instruments developed for assessing capacity to consent to treatment can be applied in principle to the context of assisted suicide. Current efforts to create an instrument for assessing decisional capacity in the context of requests for assisted suicide by the interdisciplinary German research group Forschungsnetzwerk Suizidassistenz (https://www.forschungsnetzwerk-suizidassistenz.de) funded by the German Research Foundation, for example, also take such aspects into consideration.

Limitations

One limitation of the search is the possibility of not including thematically relevant articles or instruments even if predefined inclusion criteria were met. In order to minimize this risk, the research was conducted systematically, and all articles were screened independently by two researchers. As there was only a small number of articles identified in the course of our search update and due to limited resources, the quality of the included articles was not appraised. For the analysis, one limitation consists of the focus on the four abilities model as outlined by Grisso and Appelbaum [Reference Grisso and Appelbaum7]. This model was chosen as it is widely used, but other influential frameworks for decisional capacity, such as the Mental Capacity Act 2005 [63] could also provide a relevant approach to assessing capacity in the context of requests for assisted suicide. Due to the lack of data on the practice of assessing decisional capacity, the development of the questions for the structured analysis of the applicability of the instruments to assisted suicide was based primarily on theoretical premises and only to a limited extent on (empirical) studies of practice.

Conclusions

In view of the emphasis on decisional capacity as an essential prerequisite for assisted suicide and studies that point to different approaches to assessing decisional capacity, assessment instruments that were specifically developed for the context of requests for assisted suicide could be helpful in establishing a more structured procedure. This applies in particular when these instruments are based on and combined with other important approaches, such as further developing a framework for assessing decisional capacity in the context of requests for assisted suicide or the training of potential assessors. Against the background of the heterogeneity shown in this study regarding the conceptualization and operationalization of decisional capacity and the interrelation of both aspects as well as the lack of instruments without deficits concerning psychometric properties that can also be used in the context of requests for assisted suicide, however, considerable research is required. Considering the need to operationalize a normative concept empirically, this should be carried out on an interdisciplinary basis. Additionally, it remains up for debate whether other ways of supporting the process of assessing decisional capacity in the context of requests for assisted suicide, such as developing guidelines or questionnaires and other more open tools, could also be feasible.

Supplementary material

The supplementary material for this article can be found at http://doi.org/10.1192/j.eurpsy.2025.10041.

Data availability statement

As no new data were created in the course of this review, data sharing is not applicable.

Acknowledgments

The authors would like to thank Malte Abel for his support in the screening process for this review.

Financial support

This research received no specific grant from any funding agency, commercial or not-for-profit sectors.

Competing interests

The authors have declared none.

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Figure 0

Figure 1. PRISMA 2020 flowchart.

Figure 1

Table 1. Overview of instruments assessing capacity to consent to treatment

Figure 2

Table 2. Structured analysis of the possible applicability of instruments assessing decisional capacity to requests for assisted suicide

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