ENMultiple empirical studies have revealed significant pandemic effects of COVID-19 on mental health in various populations. This study aimed to analyze the incidences of posttraumatic stress disorder (PTSD) and adjustment disorder (AjD) in national healthcare in 2018-2020 in one of the European countries Lithuania and estimate the effect of the COVID-19 pandemic on PTSD and AjD incidences in 2020. The national healthcare registry was used for estimations of diagnosis of PTSD, AjD, and major depressive disorder (MD). The study revealed that stress-related disorders PTSD and AjD are diagnosed rarely, resulting in a considerable gap between the expected prevalence and incidences of these diagnoses in healthcare in Lithuania. Moreover, a significant decline in mental disorders incidence in healthcare in 2020, in comparison to 2018 and 2019, was found, revealing that the COVID-19 pandemic had a negative impact on access to healthcare services and increased barriers for mental disorders treatment. The study indicates that major developments in building up knowledge about the effects of trauma and life stressors on mental health are needed in Lithuania and other countries to increase awareness about stress-related disorders and improve care for trauma survivors, in particular in the context of the pandemics or other large-scale disasters. Keywords: PTSD; stress related; prevalence; healthcare. [From the publication]