Table 3 Summary of significant characteristics and findings of reviewed publications based on literature review domains

Eiring Ø et al. 2015, [11]

Systematic review

To investigate patients’ preferences for outcomes associated with psychoactive medications.

16

Side effects and symptom outcomes outnumbered functioning and process outcomes.

Severe disease and hospitalisation were reported to be least desirable.

Patients with schizophrenia tended to value disease states as higher and side effects as lower, compared to other stakeholder groups.

In depression, the ability to cope with activities was found to be more important than a depressed mood.

Patient preferences could not be consistently predicted from demographic or disease variables.

High

First systematic review on patients’ stated preferences for outcomes of psychopharmacological treatments across methods and disorders.

Preferences for outcomes were elicited from varying and often small numbers of participants, with heterogeneous disorders.

Owing to the heterogeneity of methods and outcomes, quantitative summaries of the relative strengths of preferences could not be performed

Hostiuc S et al. 2018, [12]

Systematic review

To evaluate the degree of impairment in each dimension of decision-making capacity in schizophrenia patients compared to non-mentally-ill controls, as quantified by the MacArthur Competence Assessment Tool for Clinical Research instrument.

13

Effect size: differences in means, schizophrenia vs non-mental illness patients:

Understanding:

−4.43 (−5.76; −3.1, p < 0.001)

Appreciation:

−1.17 (−1.49, − 0.84, p < 0.001)

Reasoning:

− 1.29 (− 1.79, − 0.79, p < 0.001)

Expressing a choice:

− 0.05 (− 0.9, − 0.01, p = 0.022)

The odds for a decreased understanding in schizophrenia patients were about five times higher than in control groups (OR = 0.18, 95% CI: 0.12; 0.29, p < 0.001).

High

Despite the small number of studies, the results reached statistical significance in most scales, suggesting that enhanced informed consent forms profoundly improved decision-making capacity

Small number of reviewed studies.

Jeste DV et al. 2006, [13]

Narrative review

To evaluate the magnitude of the difference between schizophrenia and non- psychiatric comparison subjects reported as well as the influence of sample characteristics on the effect sizes observed.

12

Schizophrenia vs non-psychiatric comparison subjects

Effect size:

Understanding subscale (mean d = 0.88, SD = 0.40, 7 studies), Appreciation subscale (mean d = 0.93, SD = 0.34, 4 studies), Reasoning (mean d = 0.65, SD =0.34, 7 studies), Expression of choice (mean d = 0.29, SD = 0.24, 4 studies).

Psychopathology (mean d = 2.06, SD = 1.03, 4 studies). Cognition (mean d = 1.01, SD = 0.61, 6 studies).

Effect size comparing different MacArthur scales amongst inpatients with schizophrenia to non- psychiatric comparison subjects: range 0.45–1.54; median = 1.17)

Effect size comparing different MacArthur scales amongst clinically stable outpatients with schizophrenia to non-psychiatric comparison subjects: range 0.0–0.84, median = 0.53

High

The review of studies comparing structured measures of decision-making capacity between persons with schizophrenia and non-psychotic medical individuals revealed considerable variability in study design in terms of sample sizes, setting, age range of the participants, measures used to assess capacity, and the nature of the proposed study or intervention.

Decisional capacity is a context specific construct, and it is difficult to compare the absolute magnitude of decisional capacity scores across studies.

Larkin A et al. 2017, [14]

Systematic review

To determine the direction, magnitude and reliability of the relationship between capacity in psychosis and a range of clinical, demographic and treatment-related factors

23

Association between total psychotic symptoms and capacity to understand information relevant to treatment decisions:

r = − 0.45 (95% CI − 0.55 to − 0.34; =60%)

Correlation between overall symptoms and ability to appreciate information for treatment decision

r = − 0.23 (95% CI − 0.14 to − 0.32; =0%)

Correlation between total symptoms and ability to reason in relation to treatment decision making

r = − 0.31 (95% CI − 0.48 to − 0.12;=80%)

High

Only studies that included a reliable and valid assessment of capacity in adults diagnosed with a non-affective psychotic disorder and provided data on the association between capacity and at least one other clinical or demographic variable were included

Capacity was treated as a continuous variable in meta-analyses, even though in legal and clinical practice binary decisions must be made.

The correlational nature of much of the data in the meta-analysis limits a definitive assessment of causality.

Lepping P et al. 2015, [15]

Systematic review

To estimate the prevalence of incapacity to consent to treatment or admission in different medical and psychiatric settings, and compare the two

58

(35, psychiatric settings.

23, medical, non-psychiatric settings)

Inverse variation weighted prevalence for decision-making capacity for all the studies included was 41% (95% CI 35.6–46.2%). Heterogeneity was significant (Cochran Q 601; (df) 69; p < 0.001).

Psychiatric settings: the inverse variance weighted proportion of patients with incapacity was 45% (95% CI 39–51%). Heterogeneity was significant (Cochran Q 300; df 42; p < 0.001).

Medical settings: the inverse variance weighted proportion of patients with incapacity was 34% (95% CI 25–44%). Heterogeneity was significant (Cochran Q 267; df 26; p < 0.001), with inconsistency I2 at 90% (95% CI 87–93%). Variation between studies due to heterogeneity was 90%.

Psychiatric and medical settings did not differ significantly from each other in terms of the proportion of incapacity (Cochran Q 0.66; df 1; p = 0.44)

High

Only studies with valid measurement tools were included

High level of heterogeneity between studies.

Cut-off points for various tools are still being investigated.

Studies were not weighted according to their quality

Mukherjee D et al. 2014, [16]

Systematic review

To assess value-based decision making in individuals diagnosed with mental illness.

63, first meta-analysis (healthy populations - and individuals with frontal lesions - and populations with mental illness)

40, second meta-analysis (as a function of type of mental illness)

Individual study effect sizes ranged from 0 to − 1.55

Mean effect size was −0.58

(95% CI = − 0.68 to − 0.48, p < .001).

Population with lesions performed significantly worse than the population with mental illness. Q (1) = 6.57, p = .01, d = 0.52.

Population with mental illness, mean performances in individual studies ranged from − 6.72 to 10.20, average 0.45 (SE = 0.88)

High

The current meta-analyses provide a broad screen for possible impairments in value-based decision making by assessing Iowa Gambling Task performance across mental illnesses.

Limitations inherent to the Iowa Gambling Task (e.g. not specific for any single decision process)

Okai D et al. 2007, [17]

Systematic review

To describe the clinical epidemiology of mental incapacity in patients with psychiatric disorders, including interrater reliability of assessments, frequency in the psychiatric population and associations of mental incapacity

37

Psychiatric in-patients lacking capacity reached 29% (median) (IQR 22–44).

67% had mental capacity to make decisions regarding admission to a psychiatric unit

High

Studies report that most psychiatric in-patients can make key treatment decisions.

Studies are consistent in showing the reliability of mental capacity assessments; these measurements are correlated with indicators of clinical severity but not with demographic differences.

Heterogeneity of the patient groups, wide range of capacity assessment tools used, different legal standards for capacity assessment, differences in treatment choices presented to participants.

Frequency of capacity in some of the primary research was not the main aim of the study and was reported as an incidental finding. Studies were often small, and many used convenience samples.

Ruissen AM et al. 2011, [18]

Systematic review

To review the scientific literature on the relationship between competence and insight in patients with psychiatric disorders, how competence and insight are connected in these patients, and whether there are differences in competence and insight among patients with different disorders

7

Psychotic patients with poor insight are very likely to be incompetent

Psychotic patients with adequate insight are generally competent.

In non-psychotic patients, competence and insight do not completely overlap.

Most incompetent patients in this group have poor insight, but a substantial number of non-psychotic patients with adequate insight were incompetent.

Non-psychotic patients with adequate insight can be incompetent.

High

Provides evidence on the correlation between competence and insight in a wide range of mental disorders

Only English-language articles were included.

One article did not report a relevant and significant correlation between insight and competence, producing less convincing results.

Spencer BWJ et al. 2017, [19]

Qualitative systematic review

To examine the presence or absence of decision-making capacity in schizophrenia and the associated socio-demographic/psycho-pathological factors.

40

Decision-making capacity was present in 48% of people (range: 26–67%).

High

Provides robust evidence that a significant proportion of people with schizophrenia, even on inpatient wards, have decision-making capacity; that decision-making capacity is associated with clinically relevant variables, such as insight and neurocognitive performance,that it is not related to socio-demographic factors.

Use of dimensional measures of decision-making capacity in isolation in all studies

Wang SB et al. 2018 [20]

Systematic Review

To examine the decisional capacity measured by the MacArthur Competence Assessment Tools in schizophrenia.

7

Decision-making capacity in schizophrenia patients compared to the healthy control

Understanding (SMD = −0.81, 95% CI: − 1.06 to − 0.56, p < 0.001), Reasoning (SMD = − 0.57, 95% CI: − 0.80 to − 0.34, p < 0.001), Appreciation (SMD = − 0.87, 95% CI: − 1.20 to − 0.53, p < 0.001)

Expression a choice (SMD = − 0.24, 95% CI: − 0.43 to − 0.05, p = 0.01).

High

Provides consistent evidence that schizophrenia patients appear to have impaired decision-making competence in medical research and treatments.

The sample size of the included studies was relatively small.

Different MacCAT versions were used across studies.

Patients with severe medical conditions interfering with their ability to complete the assessments were excluded.

Frequent failure to blindly assess decision making capacity, which may have biased the results

Woodrow A et al. 2018, [21]

Systematic review

To identify factors that may help or hinder decision-making ability in people with psychosis measured with Iowa or Cambridge Gambling Tasks

50

People with psychosis:

-had moderately impaired decision-making ability compared with non-clinical individuals: g = − 0.57, 95% CI − 0.66 to − 0.48; I2 45% (moderate quality)

-were significantly more likely than healthy individuals to value rewards over losses: k = 6, N = 516, g = 0.38, 95% CI 0.05–0.70, I2 64%.

Within the psychosis groups, decision-making performance had:

-a small-moderate inverse association with negative symptoms: k = 13, N = 648, r = − 0.17, 95% CI − 0.26 to − 0.07, I2 32% (moderate quality),

-a small association with general symptoms:

k = 5, N = 169, r = − 0.13, 95% -0.25, − 0.00, I2 = 0% (low quality)

-no association with positive symptoms:

k = 10, N = 512, r = − 0.01, 95% CI − 0.11 to 0.08 (moderate quality)

-no association between overall psychotic symptoms:

k = 6, r = − 0.10, 95% CI − 0.21 to 0.02, I2 = 0% (very low quality).

-no association with current antipsychotic doses:

N = 171, r = − 0.02, 95% CI − 0.17 to 0.13, I2 = 0% (low quality)

High

Provides evidence that people with non-affective psychosis appear to make less effective decisions than healthy individuals when this is assessed using the Iowa or Cambridge Gambling Tasks.

The moderate difficulties they have are comparable with those observed in other clinical groups

Small sample sizes

Limitations inherent to the Iowa or Cambridge Gambling Tasks to assess decision-making capacity in mental health patients.