Introduction Employment precariousness has expanded over recent years. It needs to be analysed as part of a continuum of different employment conditions and in a multidimensional way. The aims of this study were to test the existence of a general precarization of the Spanish labour market and its association with mental health for workers in different types of contracts and whether the Employment Precariousness Scale is a better tool for health inequalities research than a unidimensional measure like temporariness.

Methods Using the revised Employment Precariousness Scale (EPRES-2010), this study calculated the prevalence of employment precariousness and poor mental health across six groups of workers according to their levels of employment precariousness and types of contract. Associations between the different groups of workers and poor mental health was analysed using Poisson regressions. All analyses were stratified by gender.

Results A higher prevalence of employment precariousness and of poor mental health was found among temporary than permanent workers. The association between precarious employment and poor mental health was stronger than that across contract types, and was somewhat stronger among permanent than temporary workers. For both women and men, a gradient of poor mental health existed by employment precariousness score for both permanent and temporary workers.

Discussion The Spanish labour market has become highly affected by employment precarization. The use of EPRES was more informative and a better tool for mental health research than type of contract alone. Creating a surveillance system to monitor the magnitude and evolution of employment precariousness as a multidimensional construct has to be a priority in order to reduce health inequalities and to evaluate the impact of policies and programs.