en Psychology and Psychiatry Original Article <div style="text-align: justify;"><strong>Background:</strong> Coronavirus disease 2019 (COVID-19) is a severe acute respiratory syndrome that emerged in early December 2019. Global proliferation, abrupt increases in confirmed cases, and the risk of self-infection have caused significant stress and anxiety among staff working in opioid treatment services (OTS). The aim of our study was to determine the psychological status of staff working in OTS during the outbreak period of COVID-19 in Tehran.&nbsp;<br> <strong>Methods:</strong> In a short-term longitudinal survey, 621 staff members, including physicians, psychologists, nurses, and social workers, who were selected using probability-based online panel. Data was gathered using online questionnaires including the Patient Health Questionnaire-4 (PHQ-4), the Brief Fatigue Inventory (BFI), and the Jenkins Sleep Scale (JSS). Longitudinal assessment of anxiety, depression, fatigue and sleep problems in three periods including pre-outbreak, outbreak, and non-epidemic outbreak was done through the online panel. Data were analyzed by paired t-test and repeated measures correlation.<br> <strong>Results:</strong> The rates of anxiety, depression, fatigue, and sleep problems of the staff working in OTS during the outbreak period were significantly higher than that of the pre-outbreak period (P<0.001), and it remained significantly higher during the non-epidemic outbreak and did not decrease significantly (P>0.05). The correlation coefficient between the anxiety, depression, fatigue, and sleep problems was significant in all three periods and the highest correlation was in the outbreak period (P<0.001).<br> <strong>Conclusion:</strong> Mental health problems of staff were common during the outbreak of COVID-19. Mental health problems of staff can limit the effectiveness of addiction treatment programs in the long time.</div> COVID-19,Opiate Substitution Treatment,Mental Health,Medical Staff, 44 48 http://nmj.goums.ac.ir/browse.php?a_code=A-10-1282-1&slc_lang=en&sid=1 Bijan Pirnia 10031947532846009121 10031947532846009121 Yes Behavioral Sciences Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Hasan Mosazadeh b.pirnia@usc.ac.ir 10031947532846009122 10031947532846009122 No Department of Psychology, Kazimierz Wielki University, Bydgoszcz, Poland Babak Lotfi 10031947532846009123 10031947532846009123 No The Human Revivification Society of Congress 60, Islamic Republic of Iran, Tehran, Iran Fariborz Pirnia 10031947532846009124 10031947532846009124 No Department of Food Science and Technology, Faculty of Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Kambiz Pirnia 10031947532846009125 10031947532846009125 No M.D, Internal disease specialist, Technical Assistant in Bijan Center for Substance Abuse Treatment, Tehran, Iran. Parastoo Malekanmehr Nona.Malekan@gmail.com 10031947532846009126 10031947532846009126 No Ph.D. student in Health Psychology, Department of Psychology, Faculty of Psychology, Tonekabon Branch, Islamic Azad University, Mazandaran, Iran.