Flexible work-time arrangements are thought to create ways of aligning work and private life and facilitate recovery. While temporal flexibility is found to generally bolster work–life balance, its effects on health outcomes are less well known. The present thesis seeks to examine if and how perceived control over working hours benefits workers’ health. Utilising a large Swedish cohort study, four empirical studies explored the association of work-time control (WTC) with subsequent mental and physical health as well as the underlying mechanisms and moderating influences.

Study I assessed the factorial structure of an instrument to measure WTC and found two sub-dimensions: control over daily hours (the length, starting and ending times of a workday) and control over time off (the taking of breaks/time/days off, paid and unpaid). Levels of control per sub-dimension were described by demographic and work-related factors for a large sample of Swedish workers. In particular, shift, public sector and female workers reported low levels of WTC.

Study II examined effects of control over daily hours and time off on depressive symptoms. Increasing control over time off was related to decreasing depressive symptoms over time, whereas only initial level of control over daily hours was associated with lower levels of depressive symptoms. For both sub-dimensions of WTC, the direction of this effect was predominantly from perceived control to subsequent depressive symptoms; reversed processes were of less importance.

Study III focused on work–life interference as one step on the causal chain between WTC and depressive symptoms and musculoskeletal complaints, respectively. For both sub-dimensions of WTC, part of the effect on depressive symptoms went through work–life interference. Reversed processes played a role between depressive symptoms and work–life interference only. Control over time off was found to mitigate work–life interference and subsequent depressive symptoms more than control over daily hours, albeit with generally small effects. Regarding musculoskeletal complaints, effects were even smaller and work–life interference appeared to be less important.

Study IV assessed gender differences in the impact of WTC on work–life interference and exhaustion regarding the mediating role of overtime hours. In a sample of knowledge workers, higher control over time off was associated with lower subsequent work–life interference and exhaustion, while control over daily hours was unrelated to both outcomes. Although men worked more overtime hours than women on average, no evidence was found for men with high control over time off/daily hours to perceive more work–life interference/exhaustion due to increased overtime compared to women.

This thesis found that higher levels of WTC were beneficial for a range of health outcomes, which was partly explained by fewer work–life conflicts. While these effects were generally small, control over time off in particular was consistently associated with favourable outcomes in health, work-life balance and working hours. Given that the level of workers’ discretion over working hours varies starkly by work and demographic factors, enhancing the availability of flexible work-time arrangements is in the interest of public health. WTC, with a particular focus on employees’ ability to take time off from work, may improve the daily work–life interface and support a sustainable working life.