The intervention comprised 8 modules which covered the following topics: (1) participation, (2) being active, (3) friendships, (4) relaxation, (5) self-acceptance, (6) communication, (7) self-actualization, and (8) cognitive restructuring (Textbox 1 provides an overview of the module aims).

Modules were spread over 4 sessions to be held at 1-week intervals. The first session started with an interactive introduction to learning to use the tablet, followed by module 1. Sessions 2 and 3 comprised 3 modules each. The fourth and final session presented module 8, followed by a reflection on all past modules and the instruction to choose which 3 tips they considered to be most important to them. These top 3 were then transferred onto a paper certificate, which participants received at the end of the study and acted as a self-help reminder. Furthermore, sessions 1 to 3 ended with a brief summary and homework assignment, whereas sessions 2 to 4 started with a reflection on the last session and a brief evaluation of the chosen homework assignment.

Adobe Captivate (2017, Version 10.0.0.192) was used to develop the intervention. The intervention was designed for use with 11.6-inch Odys Primo Win 12 2-in-1 tablet computers, which would be lent to the participants in the study. The images used within the intervention were either self-generated or license-free materials.

The intervention was introduced and led by an animal avatar: a poodle named Wohl, which references a German wordplay involving well-being. This poodle avatar explains how to navigate through the slides using the on-screen arrows and what users can expect from the program. This includes explaining symbols used throughout the program that introduce quizzes and discussions. Some quizzes prompt users to evaluate statements as helpful or unhelpful or good or bad, whereas in other quizzes users are given multiple-choice questions using drag-and-drop selection methods. Discussion slides present a question or statement that the user is encouraged to respond to or discuss together with their support worker. The main poodle avatar also provides an overview of his 8 animal friends, represented by 8 different animal avatars, that are associated with each module.

Overall, we aimed to minimize visual distractions by refraining from presenting a table of contents or navigation menu. To enhance user engagement, slides were animated where possible and were provided both on-screen text and a voice-over.

An advisory group was established in collaboration with a local information technology workshop for people with and without disabilities or mental disorders. Flyers were distributed at the workshop to inform their users about our study. Workshop staff confirmed the time and date of the 4 planned consultations with users who expressed an interest. The consultations were held at 2-week intervals, with attendance varying between 4 and 7 participants, of which at least 3 presented with intellectual and developmental disabilities. We did not employ specific inclusion or exclusion criteria for people to attend the consultations. As these attendees were not participants in a research study, we did not routinely collect information regarding their sociodemographic characteristics, but all advisory group members were adults, with more men than women attending the consultations. During each session, the researchers presented drafts of the program modules and requested feedback regarding module content, design, accessibility, interactivity, and delivery. Changes, as a result of this feedback process, were presented at consecutive meetings for further evaluation and included changing font sizes, simplifying language, increasing and simplifying program interactivity, changes to program navigation options and page layout, and the use of supportive instead of corrective feedback in exercises. Feedback that was not incorporated for the pilot study because of limited resources included the provision of male and female voice-overs, more animations, and mutable background music.

A more detailed description of the co-development process for the intervention is given by Vereenooghe and Westermann [24].

People with intellectual disabilities and their support workers from 2 residential facilities in North Rhine-Westphalia, Germany, took part in the study. Both facilities provide services for children and young adults with intellectual and developmental disabilities. Support staff were informed about the study objectives and procedures and were asked to identify potential participants with intellectual disabilities among the residents whom they supported.

We aimed for minimal exclusion criteria to reflect the heterogeneity found within the population of people with intellectual disabilities and only excluded participants who (1) had a diagnosis of autism spectrum disorders without intellectual disabilities and (2) people with severe or profound intellectual disabilities who might not be able to operate the tablets and engage with the program content. Details regarding participants’ level of intellectual disabilities was obtained by the participating support workers from the service users’ records.

The sole inclusion criterion for support workers was the requirement of a minimum of 2 contact hours per week with the participant with intellectual disabilities to ensure both participants had sufficient time together to implement the intervention.

A single-group pre-post design was used, with no control condition. Outcomes of mental well-being were assessed at pretest and posttest, in addition to mood barometers completed before each session. No follow-up data were obtained for this pilot study, for which recruitment took place from March 2018 to June 2018.

Participants were instructed to complete 1 session per week, with a maximum of 2 sessions per week. Tablets containing the program were lent to the participating organizations so people had instant access to the devices. The intervention was implemented in the regular working time of the support workers. Support workers had a facilitating role, and the intervention was intended to be used by the person with an intellectual disability as its primary user. Support workers could provide both practical and content support, for example, regarding the use of the tablet computers (eg, volume control or recharging the devices), clarifying the content (eg, repeating or reading the on-screen information), and assisting with program demands (eg, prompting the user to select an on-screen response or engaging the user in a discussion).

Ethical approval for this study was obtained from the Bielefeld University Ethics Committee. All participants received information about the study in easy-to-read language and provided written informed consent. Participants without the capacity to provide informed consent were not enrolled in the study.

Responses from the feedback questionnaires regarding the acceptability of the intervention were analyzed using quantitative content analysis of qualitative data [31]. First, all questionnaires were read to get an initial overview of the participant responses. Next, we generated codes to summarize each distinct piece of information, thereby being guided by the raw data rather than using pre-existing codes derived from the theory. For the qualitative analysis, we grouped these themes in overarching themes. For a further quantitative content analysis, the codes were then counted to identify themes that appeared more prevalent and to explore patterns in the data that could guide future development. Within this step, however, we made the decision to interpret the thematic codes as being positively or negatively valenced based on the questions that elicited these responses (eg, positively valenced questions included “which aspects did you like?” and “which content did you find helpful?” whereas negatively valenced questions, included “what did you notice negatively?” and “which content did you find unhelpful?”).

Differences in pretest and posttest scores were analyzed in SPSS (2017, Version 25) using nonparametric 1-tailed Wilcoxon signed rank tests.

The use of animal avatars was liked by the majority of people with intellectual disabilities and support workers. The interactive design, with quizzes, and use of both images and videos were also positives of the program. Support workers valued the program as a user-appropriate concept based on its audiovisual approach, the use of repetition, encouragement and supportive feedback, and session length. Given the heterogeneity of people with intellectual disabilities in terms of cognitive and communicative abilities, some support workers also rated the intervention as either too childish or difficult with regard to language. By contrast, none of the participants with intellectual disabilities mentioned the program to be childish and instead were explicitly positive about the design of the intervention.

The friendships, self-acceptance, and self-actualization modules were particularly well received by people with intellectual disabilities, as were specific tips to improve your well-being. Support workers approved the wide range of topics and the information regarding local service providers included in specific modules and also highlighted the need to provide more concrete and less abstract tips in the self-actualization module. They considered the content of the modules concerning maintaining friendships, being active, and relaxation as most helpful to the people they were supporting. Both user groups considered the communication module too difficult, which is likely because of the metaphor used to explain the different roles and aspects of good communication (ie, the talker, the listener, a conversation topic, switching talking-listening roles, and changing topics).

Technical errors in the use of the program were a main hindrance for both people with intellectual disabilities and their support workers. This applied to navigation arrows that were considered too small and buttons or interactions which were inactive. Session length was appropriate, according to support workers, and implementation should be limited to 1 session per week.

Overall satisfaction rates for the 4-week intervention were high. Participants with intellectual disabilities and support workers gave the program approval rates of 92% and 86%, respectively.

The Pudelwohl intervention, in its content and design, most closely approaches a combination of the 2 intervention arms of the Beat It trial, behavioral activation and guided self-help, both of which led to patient improvement [35]. Direct comparison of both studies demonstrates that the pilot Pudelwohl intervention resulted in higher completion rates (95% vs 81%), but also yielded lower effect sizes as our study design was not set up for evaluating intervention efficacy. A larger trial of the present intervention in a similar sample of people with at least subclinical symptoms of reduced well-being is required to more adequately compare both the interventions. A shared finding, however, is that participants with intellectual disabilities in both studies reported a desire for more sessions or an overall longer intervention [36].

Focusing on the digital components of our intervention, we found similar levels of acceptability to that of a website aimed at informing people with intellectual disabilities about good mental health [37].

In terms of customizability and tailoring the intervention to individual participant needs, our intervention offers a compromise between a more rigid design of a website and the flexibility that can be offered in a face-to-face therapy, for example, by presenting options for local activities, giving participants the option to choose those tasks that are more relevant to them, and by involving support workers who could ensure program content was discussed in a way that was meaningful to the participant. However, it is not yet clear whether the acceptability and efficacy of individually tailored digital interventions is higher than that of standard packages [38].

Contributing to the intervention’s overall acceptability is our purposeful attempt to adapt all aspects of the intervention to the variable needs of people with intellectual disabilities. This includes incorporating all but one of the suggested adaptations to psychological therapies for people with intellectual disabilities, as put forward by Hurley et al [39]. Use of a digital platform should not exempt the intervention from addressing the users’ intellectual disability; however, this disability in itself may present the person with considerable challenges and negative events in their daily lives that could contribute to poor mental well-being. In our intervention, we addressed this in Module 5 Self-acceptance, where participants were prompted to both say what they are good at and to reflect on questions such as my weaknesses are not failures, you can laugh about some mistakes, I should feel bad about my weaknesses, and my weaknesses are a part of me.

Involving support workers is generally viewed favorably when planning or delivering psychological interventions to people with intellectual disabilities [35,39,40]. When using digital interventions, their involvement can help overcome technical difficulties experienced by people with intellectual disabilities, as we found in this study. By contrast, their involvement could also present an extra barrier when support workers do not feel sufficiently confident themselves in using technologies or wish to protect the person from the potential risks associated with the use of Web-based technologies [23]. This approach could therefore lead to people with intellectual disabilities who might otherwise express an interest in digital interventions or who would have the capacity and skills to take part without the need for a support worker to be excluded from research or interventions built around the involvement of these gatekeepers. In this study, the challenges arising from such a design are apparent from the contrast between the low recruitment rate of support workers and the high interest of people with intellectual disabilities.

When a decision is made to include support workers, either as active participants or in a supporting role, attention should also be directed to any potential effects of the intervention on the support worker and their relationship with the person with an intellectual disability. This could include changes in attitudes, knowledge, or skills, as well as the quality of the relationship, which was reported to have improved by some of the support workers in this study.