Objective: In this study, we aimed to explore the prevalence and determinants of common mental health disorders (CMHDs, posttraumatic stress disorder [PTSD], depression, and anxiety) in Syrian refugees in Lebanon. Specifically, we examined how the associations between cultural adversities (discrimination, unemployment, and separation from family) and CMHDs are modified by levels of religiosity and sex. Method: Between March and June 2017, a cross-sectional study was conducted targeting adult Arab Syrian refugees residing in Beirut and Southern Lebanon. Eligibility criteria comprised being a United Nations High Commissioner for Refugees-registered Syrian refugee residing in Lebanon, 18 years and older, and having no history of mental disorder or physical disability. A total of 191 refugees agreed to participate and complete a battery of six questionnaires. Exposures were measured using a sociodemographic questionnaire, the Postmigration Living Difficulties Checklist, the Harvard Trauma Questionnaire, and the Belief into Action Scale, while outcomes were measured using the Posttraumatic Stress Disorder Checklist for DSM-5 and the Depression and Anxiety Scale-21 Items. Results: Half (50.3%) of our sample had high PTSD risk, 73.8% had high depression risk, and 73.8% had high anxiety risk. Stratified analysis revealed religiosity and sex to be effect modifiers of the associations between cultural adversities and CMHDs. Specifically, cultural adversities were only significantly associated with CMHDs in the low religiosity stratum and males. Only unemployment was a significant risk factor for PTSD in both males (OR = 4.53, 95% CI [1.44, 14.27]) and females (OR = 2.77, 95% CI [1.14, 6.74]). Conclusions: Religiosity and sex are effect modifiers of the associations between cultural adversities and CMHDs. Religious and spiritual interventions in mental health care should be adopted in refugee settings. Moreover, there is an urgent need for capacity-building initiatives addressing social determinants of mental health among Syrian refugees in Lebanon.Walaa G. El Sheikh https://orcid.org/0000-0002-4890-0222 Firas Kobeissy https://orcid.org/0000-0002-5008-6944 The authors would like to thank Blue Mission Organization for facilitating the recruitment process. The authors have no conflicts of interest to declare.Hussein Abou-Abbass and Walaa G. El Sheikh contributed equally to this study. Hussein Abou-Abbass served as lead for data curation and methodology and served in a supporting role for writing-review and editing. Walaa G. El Sheikh served as lead for formal analysis, software, writing-original draft, and writing-review and editing. Maya Bizri and Hani Tamim served in a supporting role for formal analysis and writing-review and editing. Samar Al-Hajj, Farah Allouch, Rawan Chehade, Mayssa Ghannam, Youssef Fares, and Zeina Nasser served in a supporting role for writing-review and editing. Lina Karout contributed equally to data curation and served in a supporting role for writing-review and editing. Hayat Harati served in a su...