BACKGROUND: The COVID-19 pandemic has resulted in long-term consequences for a subset of affected individuals, known as long COVID syndrome. The neurological and psychiatric effects of this condition remain incompletely understood. This study aims to evaluate heightened common mental disorders in long COVID through assessing psychiatric, cognitive, neurophysiological aspects, and emphasizing lasting mental health impacts. METHODS: This cross-sectional study compared patients with long COVID to those who had recovered from COVID-19 without residual symptoms using quantitative electroencephalogram (qEEG) analysis. We conducted qEEG analyses, and Montreal Cognitive Assessment (MoCA) and Self-Rating Questionnaire (SRQ) tests on participants. Analyses included brain spectrum examination, hemispheric asymmetry, and inter-electrode connectivity. RESULTS: Analyses revealed lower MoCA scores in the memory domain were lower in the long COVID group (Mann Whitney CONCLUSION: Our findings underscore the persistent neuropsychiatric impact of COVID-19, particularly in long COVID patients. Notably, working memory deficits in MoCA scores were identified as one of the most frequent neuropsychological symptoms in these individuals. Decreased brain connectivity indicates cognitive-sensorimotor decline and is confirmed by the frequent brain fog symptoms in long COVID.