Abstract
(1) Background: Validated instruments to measure mental health variables related to sanitary crises can provide data for prevention or intervention plans. The objectives of this study were: (1) to evidence the psychometric factorial internal structure of the Battery for Assessing Mental Health-Pandemic Version (BASM-P) in the sample; (2) to investigate the psychosocial impact of the COVID-19 pandemic in Brazilian post-peak period among individuals with and without pre-existing psychiatric conditions using the BASM-P; and (3) to analyze relationships between the mental health variables measured by the BASM-P in both groups. (2) Methods: This is an internet-based quantitative, cross-sectional study with a non-probabilistic convenience sample. The participants (n = 209) were divided into a non-psychiatric group (n = 168) and a psychiatric group (n = 41). The instruments were the BASM-P and a sociodemographic questionnaire. Data were collected throughout the second semester of 2022 and analyzed with JASP software. (3) Results: The BASM-P demonstrated robust psychometric factorial internal structure. Significant differences were observed between the two groups across all variables. In the non-psychiatric group, obsessive thoughts presented strong connections to fear, distress, and grief from job loss. (4) Conclusions: This study highlights the central role of obsessive thoughts in shaping the psychosocial impact of the COVID-19 pandemic in the Brazilian post-peak period.