Factors relevant to work participation from the perspective of adults with developmental dyslexia: a systematic review of qualitative studies

Background This review is focused on workers with developmental dyslexia (DD). In this review DD is considered an expression of neurodiversity, a consequence of a natural variant of the brain. Evidence was synthesized to explore which factors workers with DD consider relevant for their participation in work and whether these factors reflect shifts in the concepts of health and sustainable employability. The factors were classified according to the International Classification of Functioning, Disability and Health (ICF), adapted for occupational health. Methods A systematic review of qualitative studies was performed. Two search strings were used to determine the population and the context of work. The factors were classified using a recently proposed rearrangement of the ICF scheme that places participation in a central position and incorporates preliminary lists of work-related environmental factors and personal factors. Results Fifty-one factors were found that appeared in 35% or more of the included studies and that were relevant to work participation according to the workers themselves. These factors were dispersed over all ICF categories. In the category Functions and Structures (11 factors), most of the factors had negative connotations. In the category Activities (9 factors), all the factors cause difficulties, except speaking (which is ambiguous). In the category Participation (4 factors), the formal relationships are important for the degree of participation. Overall, more than half of the factors are environmental (18) or personal (9) and they both hinder and facilitate work participation. Conclusions The results of this review give an indication for the importance of the biopsychosocial model as a relevant approach for people with a disability in the world of work. This review also adds data for the usefulness of the proposals for the reconsideration of the ICF scheme. The data has not (yet) returned any visible trends revealing that the concept of neurodiversity is common in organizations. Supplementary Information The online version contains supplementary material available at 10.1186/s12889-022-13436-x.


Background
In 2014 a systematic review of qualitative and quantitative studies was performed by the same authors as the present review [1]. The aim of the review was to determine factors that hinder and facilitate work participation of people with developmental dyslexia (DD). The factors were classified according to the dimensions in Open Access *Correspondence: joost.debeer@han.nl the International Classification of Functioning, Disability and Health (ICF) [2]. The most important finding in that review was that DD affects not only activities related to writing/spelling and reading, but also many other activities as well as mental functions and participation. The extent of the impact of DD is influenced by many environmental and personal factors and increases over a person's lifetime with consequences for finding and/or maintaining meaningful work.
The first rationale for performing this review is to update the former review of 2014. In that review the influencing factors for work participation were searched in both qualitative and quantitative studies and from the perspectives of the workers with DD themselves and of the employers. This review has a sharper focus: only on workers with DD themselves and the influencing factors were searched only in qualitative studies. This choice was motivated by the broadened focus in the field of occupational health to capture the complex relationship between the working environment and health in general. That makes it necessary to understand people's experiences, behaviors, and interactions by interpreting their lived reality. Such an interpretation can provide information about a wide range of barriers to and facilitators of working with a chronic condition, such as DD, that are difficult to capture in quantitative data [3].
Another rationale for performing this review is changes in the ICF scheme. As in the 2014 review, this review used the ICF to classify the influencing factors. However, a reconsideration of the ICF scheme has been ongoing since 2017. While the original scheme placed the component 'disease' at the top, Heerkens et al. [4] have proposed rearranging this scheme by accommodating the disease in the component 'personal factors' and by giving the component 'participation' a central position.
Heerkens et al. [5] also elaborated on the contextual factors for occupational health care which resulted in a preliminary list of work-related environmental factors and personal factors. Both preliminary lists and the rearrangement of the ICF scheme were used in this review.
These changes and elaborations of the ICF are a result of some developments related to work and health. In the domain of health, there has been a shift from the biomedical toward a biopsychosocial paradigm, and from cure toward care, prevention, and a focus on functioning [4]. More attention is being paid to a disorder's impact on functioning in daily life, to the positive or negative influence of a person's character and personality traits, and to the influence of the environment (home, school/work, sports, neighborhood).
In this review DD is considered to be an expression of neurodiversity, a consequence of a natural variant of the brain [6]. Disorders that were formerly called learning or behavioral disorders (e.g., DD, dyscalculia, Attention Deficit (Hyperactivity) Disorder, Autism Spectrum Disorders, and high giftedness) are now seen as consequences of natural variants of the brain [7]. These variants can be diagnosed increasingly accurately due to the improved quality of measurement instruments. Many of these variants, like DD, are therapy-resistant and persist in adulthood [8]. Improvements in educational systems also have ensured that more attention is paid to the special needs of children and adolescents with one or more of these natural brain variants.
These factors have increased the prevalence of workers with one or a combination of these variants in recent decades [9] and have originated the concept of neurodiversity in the workforce. Advocates of neurodiversity promote a shift from complaints toward strengths [6] and assert that companies would benefit from recognizing and developing the strengths of workers with e.g. DD instead of pathologizing their weaknesses. While neurodiverse workers experience difficulties, they also bring talents to a company, such as 'out-of-the-box thinking' skills that balance 'regular thinking' skills, already present to a great extent, and different views on reality. This increases workplace diversity. But recognizing and developing these strengths requires occupational accommodations that enable such employees to access their strengths and alleviate difficulties in the pursuit of inclusive and sustainable employment [6,10]. The concept of neurodiversity affects both the work environment and the workers with e.g. DD themselves [11].
A systematic review of qualitative studies was performed with the aim to explore which factors, classified according to the adapted ICF, workers with DD themselves consider to be relevant for their participation in work. The review also explores whether these factors reflect a paradigm shift toward a biopsychosocial model and explores the impact of the concept of neurodiversity.

Identification of studies
The relevant literature was identified by using the results of a systematic literature review from 2014 of the same authors [1] and by performing new searches in the electronic bibliographic databases Business Source Ultimate (via Ebsco), Cinahl Plus with full text (via Ebsco), Embase (via Ovid), ERIC (via Ebsco), PsycInfo (via Ebsco), Pub-Med and Web of Science (Core Collection). The 2014 review considered literature from 1995 (the year in which the ADA was published) to 2013. For this review, only the qualitative studies from the 2014 review were used and they were subjected to the same procedure as the newer studies. The new systematic searches in the databases included studies published from 2013 (because that year was just partly covered in the 2014 review) untill January 2021 (the date limit for the search). The searches were focused on dyslexia, employment and qualitative research.

Terms used in search string
To determine the population the following terms were used in a controlled vocabulary and in title/abstract For 'employment' the search was optimized with the help of a medical information specialist for each database. Due to the nature of the used databases, it was necessary to adapt the different searches. This was done to keep the ratio between relevant and irrelevant results at an acceptable level. A more general search resulted in too many irrelevant studies.
For 'qualitative research' the search block with the same title was used unaltered, developed by a member of the Dutch Association of Information Professionals (KNVI) (L.J. Schoonmade), which can be found on their website [12]. The search strings and block were used in PubMed, but were modified for other databases in which different search terms are used. In all databases, the string and blocks were used in an AND-combination. Within the blocks the OR-combination was used. The complete strings per database can be found in Additional File 1.

Inclusion criteria
The set used to include studies in this phase of the review consisted of four criteria: Studies were included if they met all four criteria. The criteria were not weighted. All studies identified in the searches were checked on duplications, using the Bramer method via Endnote. Afterwards the deduplication was checked manually by two authors (JdB and JE) independently. After this deduplication process all studies were imported into Rayyan for Systematic Reviews, and this software package was used throughout the inclusion of studies.

Review procedure
Titles and abstracts of the studies identified through the search strategy were screened independently by two authors (JdB and JE). Studies that did meet the inclusion criteria were included without further examination of the full-text. Studies that did not meet the inclusion criteria were discarded. When the two authors disagreed, a consensus meeting was held to solve the disagreement.
After the immediate inclusion based on the information in the title or abstract, in the second step a study was selected for full-text examination if the title or abstract: • Left it unclear whether it was a primary study; • Left it unclear whether the descriptor 'people with learning disabilities' or '(learning) disabled people' included adults with dyslexia. The word 'dyslexia' had to be present in the Methods or Results section; • Left it unclear whether the population was still studying or was already employed; • Referred to an activity, personal factor, environmental factor or mental function without an explicit link to work Two reviewers (JdB and JE) independently scanned the full texts of these studies to determine whether additional information clarified the uncertainties mentioned above. If any disagreement remained after a consensus meeting, a third reviewer (YH) was consulted to make the final choice to include or exclude the study. Two reviewers (JdB and JE) also conducted independently forward and backward citation searching for the included references, resulting in no new inclusions.

Quality assessment
This systematic review of qualitative studies was designed to find conceptually rich studies, which are studies with sufficient depth for interpretation [13]. However, there is currently no established method to assess conceptual richness which, in itself, can be an indicator of quality. Thus, in this review quality assessment was performed to define conceptually rich studies.
Two reviewers (JdB and JE) independently used the nine questions about quality that can be asked about qualitative studies [14]: worth or relevance, clarity of the research question, appropriateness of the design, context or setting, sampling, data collection, data analysis, applicability of the results in similar settings, and reflexivity of the account. This set of criteria was chosen because of the reflexivity criterion: sensitivity to how the researcher and the research process shaped the collected data, including the role of prior assumptions and experiences [14]. This is in line with recent developments in qualitative research [15].
The reviewers graded each study on the criteria from this list and marked each as ' + = present' , '-= not present' or ' ± = insufficiently described' , without passing a final judgment of the study's quality. A minimum level of quality of at least six ' + ' and one ' ± ' was chosen, to achieve the same 70% criterion as in the 2014 review. If a study did not meet that threshold, it was excluded. To measure interrater reliability at the level of the criteria, Cohen's kappa was calculated [16].

Data extraction
For this review, study findings were extracted from the section labelled 'Results' or 'Findings' . Findings were also extracted from the ' Abstract' sections because findings in abstracts of qualitative studies are not always reported in the same way as in the text [17].
All included studies were initially described based on characteristics, some of which can influence the experience of adults with DD or the impact of DD on work. These characteristics were: aim of the study, country setting (because of the national disability legislation), characteristics of participants (number, gender, age, age at diagnosis (in relation to therapy and developing coping strategies)), setting/discipline (i.e. occupations included in the study), data collection method, data analysis method, and main findings.
All included studies were then assessed in terms of factors associated with the work participation of adults with DD. A factor is a single element or a construct that the workers with DD themselves believe to have a positive or negative influence on their work participation. A factor can be embedded in a quote from a participant (a first-order construct according to Schutz [18]) or in an interpretation by the researcher in the study (a secondorder construct). The factors had to be mentioned explicitly in the text.

Data classification
All factors were classified according to the ICF [2]. However, the ICF does not yet classify personal factors and many factors relevant to the working environment are missing in the classification of the environmental factors. Therefore, we used the elaboration of the contextual factors for occupational health care from Heerkens et al. [5] to classify the work-related environmental factors and personal factors. The concepts used are shown in Fig. 1. The factors were linked to the best fitting ICF category or best fitting contextual factor. Although the central issue in this review is 'work participation' , factors influencing work participation can be found in all ICF categories.
Two reviewers (JdB and YH) independently performed the data extraction and classification. Consensus meetings were part of this process. If a reviewer was uncertain about a factor or classification, a third reviewer (JE or JvdK) was consulted.
To visualize all the factors from the primary studies, the reviewers created an Excel spreadsheet with the ICF categories and preliminary lists on the y-axis and the primary studies, in chronological order, on the x-axis. More details and the spreadsheet itself are available in Additional File 2.
When evaluating the shift from a biomedical toward a biopsychosocial paradigm, the reviewers used the elaborations from the ICF and assigned a prominent position to the personal and environmental factors. The concept of neurodiversity was based on positive self-perceptions of workers with DD, a focus on strengths, positive attitudes of co-workers and line managers or employers, and support and accommodations in the workplace. Factors in the ICF related to these pillars of the neurodiversity concept can be found in the emotional functions (b152) and in the experience of self and time functions (b180); in individual attitudes of colleagues (e 325) and of people in position of authority (e430); and in products and technology for communication (e125) and for employment (e135).

Results
In the 2014 review 13 qualitative studies were included that reached the 70% threshold for the quality assessment. For this review, the full texts of these 13 studies were independently rescreened for eligibility based on the four criteria in the Methods section. Of these 13 studies one [19] was excluded because the data were not reported from the perspective of workers with DD themselves, but from the perspective of employers.
The additional database searches for qualitative studies on the subject from 2013 to 2021 yielded 1114 studies, 377 of which were duplicates. 737 were qualified for independent screening and were imported into Rayyan Systematic Review Software. After independent screening of title and abstract 701 studies were excluded. The remaining 36 studies required full text scrutiny: 27 had insufficient information in the title and abstract to warrant inclusion or exclusion, and 9 seemed to be eligible. These 36 studies were independently screened on the four criteria from the Methods section. Of the 27 studies with too little information in the title and abstract, 26 were excluded and 1 was included. Of the nine studies that seemed to be eligible, three were excluded and six were included. Thus the final total was 19 studies (see Fig. 2).

Quality assessment
The nine criteria for quality reported by Mays and Pope [14] were used to assess the quality of the studies. Each study was assessed based on each criterion and assigned ' + = present' , '-= not present' or ' ± = insufficiently described' . The threshold for inclusion in this review was at least six ' + ' and one ' ± ' . The studies were sorted by number of plusses; those with an equal number of plusses were sorted further by publication year and alphabetical order (see Table 1). Interrater reliability at the level of the criteria independently scored by the two reviewers was measured. For that purpose a Cohen's Kappa was calculated: 0,79, which is substantial [20]. Table 2 displays the main characteristics of each included study: aim of the study, country, characteristics of participants, setting/discipline, data collection method, data analysis method and main findings.

Main characteristics of the studies
The aims of these studies correspond with their qualitative character: they report the experiences, understandings, and impact of DD on the work of workers with DD in general, but sometimes also in specific contexts like nursing, medicine, physiotherapy, education, or transportation. One study [33] explored how technology can be supportive in the workplace, one [35] examined the impact of learning disabilities on young women's career development, one [38] explored the intersection of dyslexia, paid work, and mothering, and one [25] explored the differences between US and Canadian workplaces for adults with learning disabilities after protective legislation was introduced.

Extraction of factors
Additional File 2 contains the Excel spreadsheet mentioned above and describes how the factors extracted from the studies fit into the ICF scheme, in the category order shown in Fig. 1. For this paper, the findings were scaled to the second level of the ICF categories. On the first level, the ICF divides the main domains into chapters that are itemized at a second level. These secondlevel items are further specified into factors, mentioned        [22,23,26,28,30,31,33,38], always with a negative connotation like uncertainty or insecurity. Under Emotional functions, the connotations of the factors Fear and Feelings were also negative: fear of being stigmatized or laughed at [22,28,30,36], fear of failure or exposure [20,24,25,28,30], feeling different [25,28,29,34], inadequate or inferior [21,25,28,34] or presenting a false impression [34,37].
In the category of Activities, factors from three chapters are scored: 'Learning and applying knowledge' includes the negative factors Speed of reading [21,27,33,34,[37][38][39] and Speed of writing [21, 24, 27, 31-33, 38, 39] which are consistent over the years. The two other chapters were 'General tasks and demands' and 'Communication' . In the latter, the item Speaking had opposite connotations: speaking is challenging for some workers [30,32,37,39], while it is a strength for others [31,38].
In the category of Participation only two chapters were covered. The first is 'Interpersonal interactions and relationships' in which the item Formal relationships was exclusively used in the context of work (with colleagues [27,30,31,34], supervisors [26,30] or clients [29,33]). The second was 'Major life areas' which contained two important items: Acquiring, keeping and terminating a job and Remunerative employment. In the latter the factor Job performance was mentioned seven times [22,23,25,30,33,35,39]. But context is important to this factor: DD can affect job performance very little or very much. Changes in the organization [30], timed tasks [39], or timed job demands [34,37] can negatively influence job performance, but accommodations on the job and assistive technology [33] can enhance it. Stable job performance is an indicator of focused career development [35].
The category of Work-related environmental factors covers the first four chapters mentioned in Fig. 1. Under 'Terms of employment' , the factor Promotion/Job advancement is an issue in which context is important: some workers being demoted because of their learning disability [30], while others do not seek promotion because of problems with some skills [30,31,38] and a need for extra time [31,38]. These issues might restrict employment promotion. Some workers are promoted, with or without support from their supervisor, but job advancement often leads to more responsibilities [21,25,39] and hence more stress [23,25,28,33,34,37,38].
In the chapter of 'Social relationships at work' , in the item People in position of authority, the factor Role of employer-supervisor needs some clarification. If a worker's DD is disclosed, the employer/supervisor is a vital partner in achieving workplace success or failure [21,36,38]. Some workers hint at the positive role their employer/supervisor plays in making reasonable adjustments available [35], being willing to create a flexible schedule [38], or supporting them for a promotion [30]. The employer/supervisor also plays an important role in the factor Reactions of co-workers in the chapter of ' Attitudes' which includes explicit negative reactions, like bullying [22,37], laughing behind the worker's back [24,29,33], or disbelief [36]. Workers may fear stigmatization or criticism from colleagues [36] and compare themselves constantly to their colleagues, which may lead workers with DD to feel inadequate [21,25] or give the false impression that they are less intelligent [23]. But when a worker with DD really trusts a colleague, disclosure will follow and then collaborative work and other types of support [27]. The chapters of 'Task content' and 'Working conditions' contain clear items and factors.
In the chapter of 'Health-related personal factors ' the item Impact of LD/dyslexia has a vast scope [22,25,26,28,29,[31][32][33][34]36]: DD can have a positive impact by helping the worker become a better and stronger person (self-perception). But the impact is mostly seen as negative: DD is experienced as a definite disability that affects everyday personal and family life, schooling, work, career, and practice, social isolation, and emotional health. Interestingly, nurses [31,32] and doctors [37,39] who work for the NHS in the UK stated that DD has little impact on their ability to do their jobs. This Results section has described a selection of the factors from Additional File 2 that appear in seven (35%) or more of the included studies. Table 3 presents all 51 factors without specifying in which studies they appear. That information can be found in Additional File 2.

Discussion
This systematic review of qualitative studies found that 374 factors are relevant to work participation according to workers with developmental dyslexia themselves. Of those factors, 51 (= 13.6%) appeared in seven (35%) or more of the included studies.
In the category of Functions and Structures (11 factors) factors with a negative connotation are prevalent; only a few are assigned positive traits: perseverance/persistence, a sense of strength, or visual and out-of-the-box thinking. A positive self-perception was found in only a few cases.
In the category of Activities (9 factors) all factors cause difficulties, except speaking which is ambiguous.
In the category of Participation (4 factors), the formal relationships are important for the degree of participation. More than half of the factors are environmental (18): expressing a characteristic of the job, or personal (9): focusing on personal experience.
In the category of Environmental factors the social relationships at work and the attitudes of colleagues and managers play a decisive role in achieving successful work participation. In the context of task content, the studies reported workload, work pressure, and work stress. In the context of working conditions assistive technology for communication and accommodations on the job are helpful.
In the category of Personal factors stress experience is also an important factor. Self-disclosure remains a dilemma for most of the participants and developing learning and coping strategies is crucial for work participation. People feel the impact of DD in nearly all aspects of daily life, and it can be a barrier to success.
Of the 374 factors found, 118 (31.5%) are personal and 103 (27.5%) are environmental. This distribution indicates that the biomedical model is untenable. Context matters, as do the personality traits of workers with DD. The results of this review give an indication for the importance of the biopsychosocial model as a relevant approach for people with a disability in the world of work.
This review adds data for the usefulness of the proposals Heerkens et al. [4] made about reconsidering the ICF scheme. They proposed replacing illness or disability as the central category in the ICF scheme with the concept of functioning: an overarching term for participation, activities, and functions and structures. Functioning can be influenced by and can influence personal factors, for which an extended classification needs to be developed. And this whole is surrounded by environmental factors, that have a positive and negative reciprocal influence on functioning and personal factors. This alternative scheme was used in this review and the results have produced a good description of functioning of workers with DD, in which far more than half of the factors (221 of the 374; 59%) are personal and environmental.
As stated in the 2 section, the concept of neurodiversity can be found in several places in the ICF: in the emotional functions (b152) and in the experience of self and time functions (b180); in individual attitudes of colleagues (e 325) and of people in position of authority (e430); and in products and technology for communication (e125) and for employment (e135). Looking at the factors in these ICF categories reveals no big shifts or changes: a negative self-image and perceptions still occur, as do negative reactions from co-workers and managers. On the positive side support and job accommodations are still provided.
It is striking to note that sense of strength is not listed as a factor in the studies published after 2014. A possible explanation could be decreasing awareness of their own strengths and qualities. In line with this explanation is the disappearance of self-esteem because it is determined by achievements and accomplishments and by experiencing success. Neither factor is mentioned in the studies after 2014.
The results of this review do not give an indication for an increasing awareness of neurodiversity in the world of work. Apparently, it takes some time before theoretical concepts like neurodiversity are common in the workforce.
The quality of a working life is greatly affected by social relationships at work and the attitude of co-workers and managers. This review found that people with DD often experience these factors negatively, which is in line with the position paper by Brouwers [40] who found that employers and other stakeholders in the work environment often hold negative attitudes toward people with mental health issues. Admittedly, DD is not a mental health issue, but it has similar mechanisms. Negative attitudes decrease the likelihood that workers with DD will be supported and increase the risk of stigmatization and discrimination. The systematic review by Van Beukering et al. [41] also found that health-related stigma expressed by employers and co-workers is a barrier to sustainable employment and well-being at work for people with a disability.
For many workers with DD, disclosure (reported in 12 of the 19 studies [21, 22, 25-31, 34, 36, 37]) remains a dilemma and a complicated challenge. Whether to disclose or not depends on many factors: the worker's character and confidence, environmental safety, the line manager's attitude and knowledge, the desire for accommodations, and a fear of bullying, stigmatization, and de Beer et al. BMC Public Health (2022) 22:1083  Support from family and friends 9 Acquaintances, peers, colleagues, neighbors and community members 11 Help from colleagues / coworker assistance / buddy / mentor 8 Support in the workplace 8 People in position of authority 12 Role of employer / supervisor 8

e4 Attitudes
Individual attitudes of acquaintances, peers, colleagues, neighbors and community members discrimination. Such fear causes many workers with DD to be reluctant to voluntarily disclose their disability in advance. However, disclosure is an important condition in the disability legislation programs in different countries. The reluctance to disclose impedes the intended effect of these legislation programs on inclusion [6]. Added to that can be the strong tendency of organizations "to 'credit' all problems that the worker encounters to him or her as an individual, and to consider him or her responsible for the solution. […..] This infers that the organization does not feel a responsibility, let alone an urgency, to change or adapt or adjust the organizational context to be mere facilitating and inclusive. " ( [42], p.23). This quote also clarifies that the medical paradigm still is predominant in the eyes of employers and entrepreneurs. That paradigm is probably the biggest barrier to diversity in the workplace. The results of this review largely mirror the results from the review the authors performed in 2014 [1]. That is unsurprising given that the qualitative studies from that review, minus one, were also used in this study.
The age at diagnosis differed widely in the included studies. Six studies before 2014 reported diagnosis between 7 and 21 years of age (school and college years) [21,23,25,29,33,35]. There was no commonality in the other studies before 2014: some included a much wider age range at diagnosis [28,36], while other participants were only diagnosed in adulthood [27], diagnosed themselves [26], or the age at diagnosis is not specified [24,34]. This also applies to the studies after 2014. Comparing the studies before and after 2014 on the age at diagnosis, there seems to be no difference in the distribution of factors.
Relative to the 2014 review, the distribution of negative and positive items and factors did not change in this review. The negative items and factors are most prevalent in the included studies, and the workers only occasionally emphasized their strengths. The worker's own negative attitude toward DD remain notable.
The occupations of study participants differed between the 2014 review and this review. Eight of the 12 studies reported on in 2014 included a wide range of occupations [21,23,25,28,[33][34][35][36], and education was the context in the remaining four studies [24,26,27,29]. The seven Reactions of co-workers 10 Individual attitudes of people in position of authority 12 Negative response of employer 9

Working conditions
Products and technology for communication 11 Assistive technology 10 Products and technology for employment 8 Accommodations on the job 8

General 'mental' personal factors 19
Learning / coping strategies 18 Asking for help 7 Self-disclosure 12 Stress-experience / being stressed 7

Health-related personal factors 12
Impact of LD / dyslexia 10

Work-related personal factors 14
Successful studies conducted in or after 2014 added four contexts: medicine [37,39], nursing [31,32], physiotherapy [22], and transportation [30]. One study reported no occupational details to preserve anonymity [38]. Together with education, these four new contexts seem to include skills that are sensitive to the influence of DD: reading out loud and speaking in public and presenting (mentioned four times after 2014, but never before [30,32,37,39]), writing messages (far more factors were mentioned after 2014), and discussing [21,24,25,28,33] and sensitive to emotional experiences of others (both mentioned five times before 2014, but never after [23,24,27,33,34]). These factors seem to relate to the profession under study (i.e., writing messages in healthcare professions and discussing or being sensitive in educational professions). This review found 68 types of coping strategies (versus 39 in the 2014 review). This increase may be related to the professional contexts included in six of the seven studies after 2014: medicine [37,39], nursing [31,32], physiotherapy [22], and transportation [30]. Jobs in these contexts may require coping strategies to perform appropriately. In this sense, the increase in types of coping strategies could indicate increasing self-management and autonomy to minimalize the negative impact of DD on work participation. But this increase could also hint at decreasing support from the work environment (colleagues, line managers) that forces workers with DD to depend increasingly on themselves. Under such conditions, it is imaginable that workers with DD would hesitate to disclose their DD, as discussed above.
The more recent studies mention fewer factors related to the chapter of Terms of employment: there were 11 factors in five studies conducted before 2014 [21,25,33,35,36], but only four factors in three studies after 2014 [30,31,38]. This decrease may indicate the growing influence of disability legislation which may normalize accommodations in the work environment for workers with DD. But it could also indicate diminishing support from the work context that forces workers with DD to find their own strategies to manage the impact of DD on their work, and consequently makes them hesitant to discuss terms of employment, including asking for accommodations.

Strengths and limitations of this review
This review used the elaborated version of the ICF for occupational health care [5]. That made it easier to identify all the factors relevant to work participation, to categorize them, and to position them in the work-related dimensions.
Only the factors seen through the eyes of the workers with DD themselves were extracted, which excluded the perspectives of the people who surround them (e.g., colleagues, line managers and employers). This focus makes it possible to capture the factors that really matter and that would be invisible in quantitative studies [3].
Also the influence of the present researchers on the construction of meanings and of lived experiences of workers with DD needs to be addressed. The data to be analyzed consisted of quotes from the workers themselves or from the researchers in the primary studies. These quotes were sometimes extensive, but they could also be very short. The literal text was used to describe the meaning of a factor, but classifying a factor into a second-level ICF item is a subjective choice and an act of interpretation. To reduce subjectivity, the analysis was done by at least two authors (JdB and YH), and, in the case of doubt, by a third author (JvdK/JE). Nevertheless, it is possible that factors mentioned in the text were incorrectly interpreted and classified in the ICF or that two distinct factors may cover the same meaning. To make the interpretations and classifications auditable, the choice for an exhaustive detailing was made in the Excel spreadsheet in Additional File 2. However, the exhaustive details negatively affected the spreadsheet's clarity.
For the quality assessment the criteria list based on Mays and Pope [14] was chosen because of the additional criterion 'reflexivity' . This choice reflects our assumption that in more recent studies, researchers would be more conscious of their own influence on data collection and analysis. However, that was not the case: of the seven studies after 2014 only two made remarks about reflexivity [22,31]. That is the same proportion as in the studies before 2014 (four to twelve [21,23,26,33]).

Implications for practice
Along with Attention Deficit (Hyperactivity) Disorder (ADHD) and Autistic Spectrum Disorders (ASD) DD belongs to the 'neurominorities' as Doyle [6] defines them: the diversity within an individual's cognitive ability. DD is a chronic condition, the incidence of which has been increasing in recent decades. In education, improvements have been made in coaching children and adolescents with one or more of these conditions. Thus, in the future more people from the 'neurominorities' will enter the labor market, but this labor market is not well prepared for their arrival: there is too little knowledge of their strengths and weaknesses, colleagues and line managers often hold stigmatizing attitudes, the workers themselves may have inadequate self-management capacities, and there is too little knowledge on how to accommodate them in the workplace and give them the right type of support. These and other barriers must be overcome. There is a need for a tool in the workplace that can be used to discuss all the relevant aspects that can be influenced and that can support an increase in work participation and job satisfaction. An overview of the relevant factors may be a starting point for constructing such a tool. A better understanding of these factors, arrived at by analyzing the possible combinations and types of relationships, will enhance the inclusion of workers with neurodiverse features in the workplace.

Suggestions for further research
The factors mentioned in the Results section are part of a bigger network in which they can be combined with other factors in various relationships. Merely aggregating these factors, as this review has done, does not reveal those combinations and relationships. Therefore, another type of analysis is needed to provide a nuanced understanding of an issue (work participation of workers with DD) within larger theoretical, social, and cultural contexts. Meta-ethnography would provide that type of comparative textual analysis of qualitative studies [43]. Analyzing the textual material (the first-and second-order constructs) from the qualitative studies in this review in an ethnographic way, has already begun and the results will be reported in another article.
The central position of functioning in the adapted ICF scheme makes it easier to connect to the Capability Approach (CA) [44]. This first was done by Welsh Saleeby [45] and subsequently adopted by Bickenbach and Mitra [46,47]. The CA recognizes functionings and capabilities as central concepts. The capabilities are the real possibilities to choose from, for doing or being what a person has reason to value. The functionings are the achievements of that process and they come very close to the concept of participation [48]. The ICF and the CA can complement each other: the ICF has fewer options to express individual orientation on values in life, underlying personal aspirations, and choices, while the CA needs valid and comparable data about the health status of individuals. It would be interesting to use a combined ICF-CA framework to validate the numerous factors found in this review. With that aim, qualitative in-depth interviews were performed with workers with DD, also to operationalize the value of work for these adults. The results of these interviews will be reported in another article.

Conclusion
The results of this review give an indication for the importance of the biopsychosocial model as a relevant approach for people with disabilities in the world of work. This review also adds data for the usefulness of the proposals made by Heerkens et al. [4] about the reconsideration of the ICF scheme. The data has not (yet) returned any visible trends revealing that the concept of neurodiversity is common in organizations. As far as the increase in coping strategies is concerned, it is difficult to unambiguously interpret these results.
According to the sustainable development goals of the United Nations [49], it is a societal responsibility to employ workers with a work-related disability. This is Doyle's [6] occupational narrative around the 'diamond in the rough': the aim of occupational accommodations is to access the strengths of workers with work-related disabilities like DD and to alleviate their struggles with the goal of including a great diversity of people in the workplace, which also benefits the organization itself and society as a whole.