Occupational stress-related disorder is not only a capricious disease that pertain to health and well-being of individuals. In terms of sick leave, stress-related disorders result in lower productivity and absenteeism from work. Both of which is associated with a substantial financial cost for society [1, 2, 3]. WHO has been named stress the “Health Epidemic of the 21st Century” and estimated it to cost American Businesses up to $300 billion a year .
Occupational stress research has typically been characterized by employing self-reports methods as the primary outcome metric. However, self-report measures are potentially vulnerable to bias due to a range of factors, including social desirability or response style. Specifically, previous studies suggest that people apply different strategies when completing self-report surveys, which run the risk of producing differences in scores between participants that reflects influences other than item content. This might affect the validity of the causal conclusions for variables in question as it may not be clear precisely which properties is being measured [5, 6, 7].
1.1 Lab-based metrics vs app-based metrics
In the domain of occupational mental health there seems to be a need for reformulation of the current reliance on self-reports which provide an impetus to develop other approaches . An alternative approach is to employ research methods using lab-based neuropsychological experimental paradigms, which of course have the textbooks of scientific methodology to lean on in terms of allowing for increased control of the variables of interest. However, such an approach profoundly lacks and changes the ecological validity of carrying out research into occupational stress in larger trials and real-world designs such as the workplace. Instead, assessment of occupational stress in the workplace may be strengthened using novel approaches by adopting insights from the field of crowdsourcing whereby there is a reliance on smartphone data [9; 10; 11]. In the nascent field of crowdsourcing, there has recently been attempts at collecting task performance from neuro-psychological experimental paradigms that has been reformulated into small games outside of laboratory settings. Such studies have demonstrated have replicated data collected in well-controlled laboratory studies in experimental tasks from a range of experimental tasks including working memory (i.e. n-back tasks) and go/no-go tasks to mention a few [9, 12, 13, 14, 15, 16, 17, 18, 19].
One hypothesis that the current study is investigating, is that employing a crowdsourcing approach using cognitive games may bypass the vulnerability of the status quo in the domain of occupational mental health. A status quo that might come from factors such as social desirability and response bias that are inherent challenges when employing self-reports .
As such, this study’s experimental aim was to assess the status of mental health in the workplace among Danish companies by relying on a crowdsourcing approach. To accomplish this aim we employed covert outcome-measures by translating well-validated neuropsychological laboratory- and task-based paradigms into an app-based platform using cognitive games. An advantage was that this approach allowed us to probe cognitive games measuring working memory and response inhibition in a large cohort of participants (N = 623) that would otherwise not be possible to deploy using such tasks in a lab-based context.
A secondary aim was to investigate the effect of mindfulness and music on cognitive processing and self-reported stress in the workplace among employees in Danish companies. This also contributed to explore and target specific interventions that may promote mental health in the workplace. In the current study we thus aimed to derive cognitive effects (through covert cognitive games using an app-based platform) from two types of interventions in the workplace. The project was carried out by offering employees in Danish companies 30-day training interventions with daily exercises of respectively mindfulness, listening to music or entering the no intervention control group. Participants were randomly selected to receive mindfulness training, music listening for 10 min per day or function as the no intervention control. Both training interventions were performed on app-based platforms.
1.2 An app-based mindfulness intervention in the workplace
As an antidote to stress-induced disorders, it has been shown that mindfulness may be helpful in treatment of pathological and stress-related conditions, and with positive impact on quality of life and well-being [21, 22, 23, 24, 25, 26, 27, 28].
A broad range of research has shown that mindfulness is effectful in dampening stress and indeed increase cognitive processing [29, 30, 31, 32, 33, 34, 35]. However, it has thus far not been tested whether these salutary cognitive effects are present in an ‘ecological’ context, i.e., in the workplace. Thus, this study aimed to investigate in a large group of Danish employees if listening to music or practicing mindfulness has the same positive effect on increased cognitive processing as when these training regimes were tested in the lab [29, 30, 31, 32, 33, 34, 35].
As a behavioral therapy mindfulness seek to improve self-regulation and emotion management through systemic training [36, 37]. Such skills have recently been shown to reduce mind-wandering [38, 29, 39, 34]. Mind-wandering refers to thoughts that are not tied to the immediate task and can be linked with decreased performance on different measures including working memory capacity . Furthermore, recent research suggest that mindfulness training can reduce the effect of mind-wandering and its effect on working memory capacity during high stress [39, 35], enhances attention , increases backward digit memory span . Such results points to the fact that mindfulness has positive effects cognitive processing such as working memory capacity and mind-wandering.
1.3 An app-based music intervention in the workplace
The use of music and specifically concentration and relaxation music in this study aimed to investigate whether relaxation music might affect subject’s ability to increase focus and decrease stress, as well as compare the effects to a mindfulness intervention. Our group have in a previous study shown that both mindfulness and music exhibit effects in terms of enhancing sustained attention compared with a control group . As well as enhancing cognitive control and reduce the detrimental effects on mental fatigue . This result is supported in the literature using music, which has shown significant improvements in attention levels and working memory . Other studies have shown an effect of 30 min of listening to binaural beats in the beta-range on mood and vigilance .
Another aim of this study was to investigate a potential entrainment effect of music and compare the effects of training (30 days) to the effects of mindfulness [e.g. 29, 39, 34, 35]. There has been some research on entrainment using music with mixed results [46, 44, but see 47], thus more research is needed.
1.4 The present study
Laboratory evidence of mind wandering is frequently captured by the Sustained Attention to Response Task (SART) . Robertson et al.  defines ‘sustained attention’ as “as the ability to self-sustain mindful, conscious processing of stimuli whose repetitive, non-arousing qualities would otherwise lead to habituation and distraction to other stimuli” (pp. 747). Sustained attention can be measured by the SART. Specifically, the SART is a go/no go task that require that go-trials are more frequent and thus creates a habitual response pattern that must be periodically overwritten by the more infrequent no-go trials which require that the participant refrains from responding. Thus, the critical measure of ‘sustained attention’ yields a count of the success rate to withhold a response when presented with infrequent trials.
Previous research on mind wandering has demonstrated that it is associated with a negative effect on performance across several domains including text comprehension , increased negative mood [50, 51] and working memory capacity . Interestingly, SART performance has been shown to correlate with everyday attentional failures  which highlights the ecological validity of the task.
In this study we wished to extend the current knowledge and address the question if the effects of mindfulness relative to a comparable music intervention on cognitive processing could be captured using app-based metrics.
Specifically, our hypotheses were:
- The app-based metrics, i.e. the cognitive games would show comparable effects in terms of working memory capacity, and mind wandering relative to validated lab-based metrics such as SART.
- The mindfulness group would show significant effects over the intervention period, which would be read-out as increasing working memory capacity, decreasing mind wandering capacity and decreasing self-reported stress as a function of time (pre vs post).
- The non-intervention control group would not exhibit changes in working memory capacity, and mind wandering capacity over time (pre vs post).