Tehran University of Medical Sciences Journal of Sleep Sciences 2476-2938 2 1-2 2018 02 13 40 45 EN Najmeh Khosrovanmehr Department of Psychology AND Behavioral Sciences Research Center, Shahid Beheshti University of Medical Sci-ences, Tehran, Iran Leila Mokhtari Department of Psychology, Office of Education of Tehran Province, Tehran, Iran Sepideh Rajezi Esfahani Department of Clinical Psychology AND Behavioral Sciences Research Center, Shahid Beheshti University of Medi-cal Sciences, Tehran, Iran Yousef Fakour Deputy of Research and Technology, Ministry of Health, Tehran, Iran Somayeh Nejati Department of Psychology AND Behavioral Sciences Research Center, Shahid Beheshti University of Medical Sci-ences, Tehran, Iran Narjes Rahmati Department of Psychology AND Behavioral Sciences Research Center, Shahid Beheshti University of Medical Sci-ences, Tehran, Iran Zahra Gohari Kamel Department of Psychology of Exceptional Children AND Behavioral Sciences Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran 2017 05 29 2017 08 20 Background and Objective: Night work causes disorder in the sleep-wake cycle followed by physiological and psychological consequences. This study aimed to investigate the effects of shift work on mental health and sleep prob-lems among workers of one gas refinery in Iran. Materials and Methods: This study was a descriptive, type ex post facto study. The sample consisted of shift and day workers of one gas refinery in Iran. A total of 255 workers were selected from the refinery by purposive sampling (126 day workers and 125 shift workers) and were evaluated using scl-90-R, Pittsburgh Sleep Quality Index, and demo-graphic questionnaires. Data were analyzed through SPSS using t-test, one-way ANOVA, and regression methods. Results:The findings suggested that there is no significant difference between shift workers and day workers in terms of mental health (M = 0.38 in day workers vs. M = 0.40 in day workers). There was a non-significant difference between shift workers and day workers in terms of sleep problems (M = 5.43 in day workers vs. M = 6.33 in shift work-ers); however, the differences between two groups in sleep latency and sleep efficacy were significant. The findings also suggested that marital status and place of residence of workers have no significant effect on sleep problems or their mental health. Conclusions: It seems that although sleep problems are more common in shift workers than in day workers, there were no significant psychological problems between these groups in our sample. https://jss.tums.ac.ir/index.php/jss/article/view/66