In this study, nine subgroups of workers with various degrees of potential vulnerability were identified based on their employment terms and working conditions. Three subgroups presented combinations of multiple unfavourable working conditions (i.e. class 4, 6, 7). The other subgroups were characterized by one or no unfavourable conditions. A significantly higher burnout symptom score underscored the vulnerability of class 4 compared to all other subgroups. However, burnout symptoms were not necessarily higher in classes that seemed most vulnerable based on their working conditions, as two subgroups without striking unfavourable conditions had the second and third highest scores on burnout symptoms.

Compared to previous studies, several similar typologies emerge. Typologies characterized by physically demanding work, in combination with low autonomy and/or high workload, are also found in previous studies (Eurofound 2016; Vanroelen et al. 2010). Similarly, distinct job typologies characterized by high job insecurity have been identified (Jonsson et al. 2021; Klug et al. 2019; Peckham et al. 2019), just as typologies characterized by practically no adverse job characteristics (Jonsson et al. 2021; Klug et al. 2019). In contrast to previous studies (Jonsson et al. 2021; Klug et al. 2019), flexible contracts and multi-job holding had limited discriminative power in determining distinct job typologies. This may be explained by the notion that compared to other countries, it is rather common in the Netherlands to have a flexible contract or hold multiple jobs (Eurostat 2023a, b).

While employees in class 4 and class 6 were similar regarding low educational level, high physical strain and low autonomy, they differed regarding having a high workload and, more importantly, regarding burnout symptoms. Given the answer categories of the UBOS, a mean value of 3 indicates monthly burnout symptoms. As we are looking at average group scores, this suggests that a substantial proportion of employees in class 4, with an average score of 2.91, may experience burnout symptoms monthly.

The relatively high score on burnout symptoms in class 4 compared to class 6 may be attributed to the combination of high job demands (physically demanding work and a high workload) and a lack of resources (low autonomy). Research has demonstrated that burnout is often a consequence of high job demands, i.e., aspects of work that require prolonged physical, emotional, or cognitive effort (Demerouti et al. 2001; Alarcon 2011). This effect is intensified by the absence of resources such as social support, autonomy, and skill variety (Bakker and Demerouti 2017; Lesener et al. 2019). An additional or alternative explanation is rooted in the demographic composition of class 6, predominantly comprising individuals aged 15 to 24 engaged in part-time on-call or no fixed-hour contracts working in service and sales and elementary occupations. Because these positions may pertain to part-time jobs held explicitly by students, which often entail limited working hours, this circumstance could explain why the combination of unfavourable conditions does not manifest in burnout symptoms.

Surprisingly, classes 3 and 8 exhibit relatively high scores on burnout symptoms, while these classes were not characterized by specific combinations of unfavourable working conditions. However, in class 3, most employees work in the education or healthcare and social services sector, where employees generally exhibit relatively high levels of burnout symptoms (Bridgeman et al. 2018; Garcia-Arroyo, Osca Segovia, & Peiró, 2019; van den Heuvel, Fernandez Beiro, & van Dam, 2022). The high score on burnout symptoms in class 8 also does not appear to be directly attributable to a specific combination of unfavourable working conditions, although almost all employees in this class have worked for the same employer for less than a year, which, in combination with a temporary contract, may contribute to job insecurity (Dekker and Schaufeli 1995).

Considering the findings of class 9, which also comprises a substantial number of highly educated individuals and simultaneously exhibits a relatively high score on burnout symptoms, it suggests a distinct manifestation of vulnerable conditions compared to the relatively lower-educated employees in classes 4 and 6. While in these classes, the predominant factors were physically demanding work and low autonomy, class 9 exhibits a substantial group of individuals who work 48 h or more per week and do this on-call or without fixed hours. Working long hours has previously been associated with poor mental health outcomes like burnout (Hu et al. 2016), which may be amplified by the fact that working hours were not fixed.

The current study’s strengths are the large sample size and representativeness of the Netherlands Working Condition Survey (NWCS) (Hooftman et al. 2020). Data from the NWCS enabled the exploration and identification of groups sharing a common set of unfavourable working conditions. By relating the identified classes with varying degrees of potential vulnerability to burnout symptoms, we also quantified the potential vulnerability first. A limitation of this study is the cross-sectional design, making it impossible to draw conclusions about causation. This study could not establish whether burnout symptoms are the result of specific combinations of working conditions or whether people with burnout symptoms are selected to work with unfavourable conditions. Second, we did not adjust the comparison of burnout symptoms between the identified classes for potential confounding variables. Therefore, future research should investigate whether our results hold when considering other factors like chronic health conditions. Third, there is some risk of information bias as all information is based on self-reports. Objective data on employment terms through registry data or medical diagnosis through linkage with healthcare providers may limit the risk of information bias in future studies.

Study results offer some leads for future research. Findings from this study indicate that determining vulnerability in the labour market is not straightforward, as not all profiles that presented clusters of unfavourable working conditions scored high on burnout symptoms, while profiles lacking such unfavourable clusters demonstrated elevated levels of burnout symptoms. Therefore, future research should investigate whether findings are similar for other mental health outcomes, which working conditions are indispensable for determining vulnerability, and which ones do not contribute substantially. Results from this study suggest, for example, that having a flexible contract and having multiple jobs does not contribute substantially to the classification of vulnerability profiles in the Netherlands. Additionally, future research could further explore the role of other potentially relevant working conditions by incorporating them into the classification, such as social relationships at work (e.g., support from colleagues, rewards, organizational justice) or emotional demands. Furthermore, future studies could examine whether potential vulnerability also translates to functioning at work (Abma et al. 2018). Moreover, burnout symptoms are distinct from the actual diagnosis of burnout. Currently, there is no consensus about a cut-off value for a burnout diagnosis. Therefore, more research is needed on the clinical relevance of these scores. Finally, future research could also qualitatively investigate what factors contribute to different groups having varying degrees of vulnerability and how this influences burnout symptoms.