Objectives Night work is suggested as a risk factor for mental health. The objectives of this study were (i) to test the association between the duration of exposure to night work and mental health, evaluated through depression and minor psychiatric disorder (MPD) and (ii) to assess the relationship between intention to leave the night shift and mental health.

Method A cross-sectional study was conducted among 432 workers (physical doctors and nursing personnel) at two hospitals in Manaus, Amazonas State, Brazil. Depression condition and MPD were assessed by PHQ-9 and SRQ-20, respectively. The statistical analyses (bivariate, multivariate logistic and multinomial regression) were conducted at SPSS (v.18.0).

Results Female workers, those younger than 38 years old, with children under the age of 6 showed higher prevalence of depression and MPD compared to their counterparts. No significant association was detected between time of exposure to night work and mental symptoms. After adjusting for age, sex, education and children’s age, night workers that intended to leave this work schedule showed greater chance of MPD (OR=2.14; 95%IC:1.09–4.23) when compared to those who did not express such a will.

Conclusions The time of exposure to night work does not seem to be relevant for the symptoms of mental health here studied. Analysing the intention to leave night work revealed to be an adequate approach to identify workers who are less tolerant to night work, thus possibly detecting those with higher chances of being affected as to their mental health.