The study used a mixed methods design, combining quantitative and qualitative procedures across the development and pilot-testing phases of the MENTALSED tool. The project began with a review of the existing literature on mental health assessment in people with intellectual disability [21] to identify available assessment tools, methodological limitations, and unmet needs in this field. Subsequently, a survey was conducted with professionals working directly with people with intellectual disability in health and social care settings with the aim of gathering their perspectives on mental health assessment and identifying specific needs in routine practice (n=31). This was carried out from January 1 to February 10, 2025.

The needs identified included the limited availability of digital tools, objective measures, and self-report instruments adapted for people with intellectual disability. On the basis of these findings, the MENTALSED assessment system was designed as a digital, multimodal tool using an EMA methodology, with self-report and proxy-report questionnaires and objective psychophysiological recordings. Two different questionnaires were developed to assess emotional, cognitive, and behavioral indicators related to mental health, one for professionals and the other for people with intellectual disability. The version for professionals also recorded medication changes and disruptive behaviors, whereas the self-report version for people with intellectual disability included sleep quality. Both questionnaires allowed complementary audio information and were designed to be completed in less than 4 minutes.

First, the questionnaire for professionals was developed using both ad hoc items and adaptations of existing standardized instruments. Once the initial item pool had been created, the questionnaire was distributed via Microsoft Forms [22] to university experts (n=6) and direct care professionals (n=10). Participants answered anonymously and evaluated the clarity, coherence, and relevance of the items and were also invited to provide qualitative suggestions regarding possible omissions or modifications. On the basis of their feedback, the questionnaire was revised and subsequently implemented on the Avicenna Research platform [23], a platform that allows questionnaires to be presented on mobile phones or tablets, sends automatic notifications, and records responses digitally, facilitating its use in natural settings and in the repeated assessments characteristic of EMA [24,25].

In parallel, the self-report questionnaire was developed by adapting ad hoc items and selected content from existing standardized instruments. Whenever possible, items were designed to be conceptually symmetrical with those included in the professional version, while ensuring accessibility for people with intellectual disability. To this end, the questionnaire was adapted into an easy-to-read format with the support of a focus group composed of people with ID (n=4), who were informed about the project and gave their consent to participate. Subsequently, a simulated version of the questionnaire was distributed via Microsoft Forms [22] to people with intellectual disability (n=16) and professionals (n=24) who answered anonymously. People with intellectual disability completed the evaluation in an easy-to-read format and were asked whether the items were important and adequately represented the construct being assessed. Professionals evaluated the clarity, coherence, and relevance of the items. In both cases, participants were invited to indicate whether any relevant aspect was missing or whether they would modify any part of the assessment. Data on the designed questionnaires were collected from professionals and people with intellectual disability from March 1 to May 30, 2025. After reviewing the responses, the necessary changes were incorporated and the self-report questionnaire was implemented using the Avicenna Research platform [23].

In addition to the questionnaires, objective psychophysiological measures were included in the evaluation to assess physiological health: HRV recorded via a chest strap and data on sleep quality and heart rate recorded via a smartwatch. Finally, all the data collected—including self-reports, third-party reports, and psychophysiological measures—were entered into a custom-developed app where they were displayed graphically in 4 dimensions: emotional well-being, general psychofunctional well-being, quality of rest, and physical well-being. Examples of this app can be seen in Figures 1 and 2.

Across the different phases of the study, 71 professional contributions and 20 contributions from people with intellectual disability were obtained. In the initial phase, direct care professionals working with people with intellectual disability completed a preliminary survey (n=31). Subsequently, during the validation of the proxy-report questionnaire, university-based experts (n=6) and direct care professionals (n=10) evaluated the items. For the development of the self-report questionnaire in an easy-to-read format, an experts-by-experience panel composed of people with intellectual disability (n=4) was involved. In the subsequent evaluation phase, people with intellectual disability (n=16) and professionals (n=24) assessed the items.

Following this period of development of the assessment tool, a pilot study will be conducted to evaluate its feasibility and functionality. The pilot testing of MENTALSED is designed to be carried out over a 2-week period, during which repeated data will be collected in naturalistic contexts using digital devices. The inclusion criteria for the pilot study are as follows: having an intellectual disability or being a direct care professional working with individuals with intellectual disabilities, having sufficient ability to use a digital device with or without support, and having sufficient cognitive ability to reflect on one’s own emotions and psychological states. The exclusion criteria are as follows: psychological or physical conditions that prevent continuous participation in data collection and an inability to understand spoken or written language. It is estimated that a minimum of 5 people with intellectual disability and 5 professionals will participate, recruited using a convenience sampling strategy based on feasibility, willingness to participate, and the existence of a regular support relationship between the professionals and the individual with intellectual disability.

The procedure will begin with an initial session in which participants will receive information about the study and provide informed consent, and professionals will complete a demographic and background form for the person with intellectual disability. The background form includes information on additional diagnoses and medication. During this first session, verbal information about the study will be provided along with an informational sheet containing the key details and contact information for the principal investigators. For people with ID, this documentation is planned to be adapted into easy-to-read format; the informational sheet will be read with them when deemed necessary, and they will be encouraged to ask questions. The consent form for participating in the study will also be adapted into an easy-to-read format and read with the person with intellectual disability if necessary. In cases where these individuals have a legal guardian or custodian, the consent form will be provided to that person for signature. Although professionals can report on more than one person with ID, for the purposes of the pilot study, each professional will be paired with a single participant with intellectual disability and will provide responses exclusively about that person throughout the study period. The pairing of a professional with an individual with intellectual disability will be done on a convenience basis, respecting what the workplace and professionals deem most appropriate (eg, if a professional regularly works with a person with intellectual disability, it may be more appropriate for that professional to respond on behalf of that person rather than on behalf of someone else they do not regularly work with). Although professionals can provide support to more than 1 person with intellectual disability in their usual work setting, each professional will provide proxy-report information exclusively about the paired participant throughout the study period. This one-to-one pairing is adopted to ensure consistency in proxy reporting and to facilitate comparison between self-report and professional proxy-report information.

To collect data, the questionnaires designed will be administered using Avicenna Research [23]. The Avicenna Research app will be installed during this first session on participants’ smartphones, when available, or on tablets provided by the research team. Participants will receive brief training on how to use the app. Objective data collection procedures will also be explained, including the use of the Polar Unite smartwatch and Polar H10 chest strap for HRV recording [33]. Devices will be provided to participants for continuous use during the study period.

Following the initial session, data collection will be carried out over 2 weeks, from Monday to Friday, resulting in 10 assessment days. The initial protocol specified that assessments through the Avicenna Research app would be completed 3 times per day by both professionals and people with intellectual disability, with automated reminders delivered to their devices. However, following consultation on the questionnaire design, this was modified to allow for only 1 assessment per day at a semiflexible time for both professionals and people with intellectual disability. Professionals will receive email notifications prompting them to complete the Avicenna Research questionnaire at the end of their workday (this can be in the morning or afternoon). People with ID will preferably complete the questionnaire in the morning, a time selected to facilitate the reporting of sleep-related variables. At the same time, a trained research technician will conduct HRV assessments under resting conditions for 10 minutes, following standardized procedures and attempting to maintain stable environmental conditions across assessment days. During the first days of data collection, the technician will also remind participants to complete the Avicenna Research questionnaires; this support is intended to be gradually withdrawn once the routine has been established. Throughout the study period, the technician will also be responsible for charging the Polar Unite [33] devices and downloading the recorded data on a weekly basis. After participating in the project, professionals and people with intellectual disability will have access to the custom-developed app, where they can view results in graphical form (Figure 3).

The primary aim of the pilot phase is to evaluate the feasibility of implementing the MENTALSED protocol in naturalistic settings. The primary feasibility outcomes are completion, adherence, usability, acceptability, missing data, and device-wear time. Completion and adherence are defined as the proportion of scheduled EMA questionnaires completed by people with intellectual disability and professionals over the 10 assessment days. The protocol will be considered feasible if at least 70% of scheduled assessments are completed. Device-wear time is evaluated through valid physiological recordings. For the Polar Unite smartwatch, valid wear time is defined as sufficient daily recording to obtain usable heart rate, sleep-related data, and daily activity; for the Polar H10 chest strap, valid HRV assessment is defined as successful completion of the scheduled 10-minute resting recording. The benchmark for physiological feasibility is valid data on at least 70% of study days. Missing data are defined as unanswered questionnaire items, incomplete assessments, or unusable or corrupted physiological recordings, with a benchmark of less than 20% missing or unusable data. Usability and acceptability are assessed through poststudy qualitative feedback from professionals and participants with intellectual disability. This benchmark is considered met if feedback indicates that the protocol can be integrated into daily routines and no critical unresolved usability barriers are identified.

Prior to formal statistical testing, a meticulous data processing and cleaning phase will be conducted to ensure the integrity of the database. Feasibility outcomes will be summarized using descriptive statistics, including frequencies, percentages, means, SDs, medians, and ranges, as appropriate. Completion and adherence will be calculated as the percentage of completed assessments relative to the total number of scheduled assessments. Missing questionnaire data and invalid physiological recordings will be reported separately.

Following data preparation, descriptive analyses will be carried out to characterize the sample and summarize the key variables under study. These analyses will include calculating means, SDs, frequencies, and percentages to describe participants’ demographic profiles, baseline clinical characteristics, and overall adherence and completion rates for the EMA protocol.

Repeated-measures data will be analyzed using exploratory linear mixed-effects models when the number of observations, distribution of the variables, and model convergence permit. The main outcome variables will be daily emotional well-being and daily psychofunctional and psychological well-being scores derived from the EMA questionnaires. For models examining change over time, assessment day will be included as a fixed effect. For models comparing self-report and professional proxy-report information, report source will be included as a fixed effect. When physiological data are available, HRV indices, particularly root mean square of successive differences, will be examined as exploratory predictors of daily well-being outcomes. Random intercepts for the participant or dyad will be included to account for the repeated-measures structure. Given the small feasibility sample, random slopes will not be estimated unless supported by the data.

Missing questionnaire data will not be imputed for the primary feasibility analyses. Available-case analyses will be used for descriptive summaries, and mixed-effects models will be estimated using maximum likelihood procedures under the missing-at-random assumption when applicable. Missing or invalid physiological data will be treated as feasibility outcomes and reported separately.

Agreement between self-reports from people with intellectual disability and proxy reports from professionals will be examined using paired daily comparisons, graphical inspection of individual trajectories, correlation analyses, and mixed-effects models including report source as a fixed effect. These analyses will be interpreted as exploratory and will be used to assess whether both sources provide convergent or complementary information.

All procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation and with the Declaration of Helsinki of 1975, as revised in 2013. All procedures involving human participants and patients were approved by the Deontological Commission of the Universidad de Valladolid (2025-CEUVa-017-H-1-Y-4). No financial compensation was provided for participating in the study. Written informed consent was obtained from all participants and, when required, from legal guardians.

The present study describes the development and pilot testing of MENTALSED, a digital multimodal system designed to improve mental health assessment in people with intellectual disability. The system integrates EMA, self-report and proxy-report questionnaires, and psychophysiological measures with the aim of providing a more continuous, contextualized, and person-centered assessment of emotional, cognitive, and behavioral indicators.

One of the main contributions of MENTALSED is its potential to capture dynamic mental health patterns that may not be detected through traditional single time point assessments. The use of EMA allows repeated data collection in naturalistic contexts and may facilitate the early identification of emotional and behavioral changes. This is consistent with previous research highlighting the value of EMA [11] in reducing recall bias and improving ecological validity [25]. However, EMA studies must be designed carefully. Our initial design called for 3 daily assessments, but these were discarded after consulting with the professionals, as they found them unmanageable in their work. This is in line with previous studies where lower-frequency, longer-duration protocols were associated with higher compliance [16] and is consistent with evidence suggesting that completion rates in EMA-based studies may be influenced by cognitive demands and assessment burden [13,16]. In contrast, more intensive protocols resulted in lower compliance in previous studies [15].

A second relevant contribution is the combination of self-report and proxy-report information. Traditional assessment in people with intellectual disability often relies heavily on external informants, which may limit the detection of internal experiences [35]. The lack of cognitively accessible self-report measures contributes to underrecognition [35]. Accordingly, the development of an accessible self-report format in MENTALSED is consistent with evidence-based recommendations [36]. At the same time, the proxy-report questionnaire provides complementary information. Comparing both sources may help identify convergences and discrepancies, reinforcing the need for multimethod approaches [14]. Recent evidence also suggests that proxy measurement of internal states presents limitations, reinforcing the need to combine proxy reports with self-report data [37]. Moreover, this multimodal structure may help reduce the risk of diagnostic overshadowing [7].

The inclusion of psychophysiological measures represents an additional strength. HRV has been associated with psychophysiological regulation and emotional states in daily life [19]. In people with intellectual disability, HRV monitoring has been explored as a potential marker of changes in behavioral excitation [38]. This multimodal approach is aligned with research combining physiological signals and subjective data [18,20]. However, physiological indicators from wearable devices should be interpreted cautiously alongside self-report and behavioral information [39]. The use of digital tools may also facilitate data storage, management, and visualization, generating individualized profiles. This could support decision-making processes in care contexts. This is consistent with work highlighting the value of mobile technologies [12] and continuous monitoring [14]. However, digital familiarity does not imply immediate usability.

MENTALSED represents a promising digital and multimodal approach. By integrating accessible self-report, professional proxy-report, EMA, and psychophysiological data, the system may contribute to more accessible, continuous, and person-centered assessment models.