A legal cap on overtime hours was implemented to control overwork as part of the labor reform law enacted in 2019. However, research that rigorously examined the relationship between workers' work and rest patterns and their mental health is scant, both in Japan and abroad. This paper reviews previous studies for the association between work and rest patterns and mental health, clarifies existing issues, and introduces the research by Sato, Kuroda, and Owan (2020), which investigates how various work schedule characteristics affect workers' mental health using detailed attendance records in a Japanese manufacturing company. The advantage of using personnel records is that the dataset has few measurement errors and little sample attrition. Controlling for unobserved heterogeneity, the paper estimates the association between four measures of work schedule—overtime hours worked, the number of hours worked after midnight, the frequency of short rest periods, and the frequency of working on weekends—and workers' mental health. Our results imply that it is important to use appropriate indicators for each occupation taking into account the differences in work schedules across job types, not just the number of overtime hours worked, in order to correct the habit of working long hours.