We assessed 27 outpatients with schizophrenia in the University Department of Adult Psychiatry of Montpellier, France between April 2021 and April 2022. The average chlorpromazine equivalent dose was 664 ± 417 mg/day. Among the patients, 90% were receiving a first-generation antipsychotic treatment, 8% a second-generation antipsychotic treatment, and 2% of patients were receiving a combination of such treatments. The proportion of patients with a score ≥ 25/30 on the MoCA was 37% (10). Inclusion criteria were: (a) age between 18 and 60 years, (b) a DSM-5 diagnosis of schizophrenia, and (c) adequate proficiency in French. Exclusion criteria for all participants were: (a) known neurological disease and (b) history of learning disability/developmental disorder.

This study was conducted in accordance to the ethical standards described by the Medical Research Involving Human Subjects Act (WMO) and was approved by the hospital’s institutional review board (IRB ID: 202100768). Written informed consent was obtained for all participants.

Sociodemographic and treatment information (for both antipsychotic medication and COVID 19 vaccination) were collected from the electronic medical records. Capacities to consent to antipsychotic treatment and COVID-19 vaccination were assessed during the same session by the same clinical psychiatrist. Psychotic symptoms were assessed with the Positive and Negative Syndrome Scale [PANSS; (11)], insight with the G12 item of the PANSS and cognition with the Montreal Cognitive Assessment [MOCA; (12)]. Due to the French vaccination strategy, patients were not offered vaccination at the psychiatric outpatient facility but in mass-vaccination centers, and retail pharmacies.

Capacity to consent to antipsychotic treatment (CC-A) and COVID-19 vaccination (CC-V) were assessed with the MacArthur Competence Assessment Tool for Treatment [MacCAT-T; (13, 14) for the French validation]. We used two measures of capacity for each participant. A measure for COVID-19 vaccination (6) and a measure of competence to consent to antipsychotic medication (13). For each decision-making capacity: the patient’s understanding of the disorder/disease and treatment-related information (Understanding) was rated from 0 to 6; appreciation of the significance of that information for the patient, in particular, the benefits and risks of treatment (Appreciation), was rated from 0 to 4; the reasoning ability of the patient (Reasoning) was rated from 0 to 8; and ability of the patient to express a choice between the proposed treatment (i.e., antipsychotic or COVID-19 vaccine) and an alternative treatment (Expressing a choice) was rated from 0 to 2. Patients were divided into two groups based on ratings on the four subscales of the MacCAT-T and on the methodology of Elzakkers et al. (15). For all subscales a patient could rate poor (50% or less of the maximum rating on that subscale), intermediate (51–75% of the maximum rating) or good (76–100%). If a patient had a poor or intermediate rating on one or more of the four subscales, this patient was considered as having diminished mental capacity.

Statistical analyses were performed with the Jamovi statistical computer software [The jamovi project (2021). jamovi. (Version 1.6) Retrieved from http://www.jamovi.org]. The χ2 and Mann–Whitney tests were, respectively, applied for qualitative and quantitative variables. Significance was set at a p value less than 0.05.

Just under two-thirds of patients had a full vaccine status (58.8%). Note that around 80.1% of the general population had a full vaccination status (according to Sante Publique France https://www.santepubliquefrance.fr/dossiers/coronavirus-covid-19). This indicates that our sample of patients was under-vaccinated compared to the general population as shown in most of the studies on this topic and whatever the different phases of COVID-19 vaccination (16). As documented in Table 1, diminished mental capacity to consent to antipsychotic medication was observed and ranged from 66.7% for the Expressing a choice dimension to 77.8% for the Understanding dimension. With regard to the competence to consent to COVID-19 vaccination, these proportions varied from 18.5% (Expressing a choice) to 63% (Understanding).

The percentage of patients with diminished or preserved capacity to consent to COVID-19 vaccination among patients with diminished capacity to consent to antipsychotic treatment according to MacCAT dimensions are documented in Figure 1. For the four dimensions of the MacCAT, we did not find a significant association between the capacity to consent to COVID-19 vaccination and the capacity to consent to antipsychotic medication (respectively, Understanding, p = 0.45; Appreciation, p = 0.60; Reasoning, p = 0.43; Expression a choice, p = 0.08). Descriptively, among patients who did not have the capacity consent to antipsychotic treatment, there is more than one-third with preserved capacity to consent to COVID-19 vaccine for Understanding (38.1%), Appreciation (33.3%) and Reasoning (33.3%) MacCAT dimensions.

Our results indicated that in individuals with reduced capacity to consent to antipsychotic treatment (CC-A), approximatively one-third had preserved capacity to consent to COVID-19 vaccination (CC-V). This result is in accordance with those of Spencer et al. (17) who showed that people with schizophrenia commonly retain decision-making capacity for research despite lacking decision-making capacity for antipsychotic treatment. In addition, no relationships were found between the sub-dimensions of CC-A and CC-V indicating that decision-making capacity is not an unidimensional phenomenon in schizophrenia and vary across domains.

Secondly, we also found that whereas reduced CC-A was associated with higher level of psychotic symptoms and with poor insight, reduced CC-V was positively associated with cognition. These results are in line with the view that CC-A is mainly influenced by how patients with schizophrenia acknowledge the presence or severity of their disease and consequently the need of an antipsychotic treatment, whereas other decision-making capacities (including decision-making capacity for other treatment than antipsychotic or research) are more related to cognitive abilities (13, 15).

In our study, and following the methodology of Elzakkers et al. (14), 77.8% of patients had diminished capacity to consent to antipsychotic treatment. The fact that most of our patients in our study were not considered as having the capacity to consent to antipsychotic treatment substantially differs from other studies (18). In most of the existing studies study using the MacCAT-T, and in order to create two groups (full and diminished mental capacity) most of the authors used a rating of 50% or less on a subscale to indicate a poor outcome and any rating over 50% as a good outcome (18). In the present study, for every subscale, a patient could rate poor (50% or less of the maximum rating on that subscale), intermediate (51–75% of the maximum rating) and good (76–100%). If a patient had a poor or intermediate rating on one or more of the four subscales, he was considered as having diminished mental capacity on the MacCAT-T. In other words, the more severe cut-off used in our study to consider a patient as having a diminished capacity to consent to antipsychotic treatment might explain this result.”