This structured literature review (SLR) investigates the mental health impacts of long COVID-19 on the UK population, focusing on depression, anxiety, and sleep disturbances. Long COVID-19, characterized by persistent symptoms extending beyond the acute phase of the infection, has emerged as a significant public health concern.A systematic search of PubMed and PsycINFO (2019–2024) identified relevant quantitative studies. Average reported prevalence included anxiety (40–43%), depression (34–37%), and sleep disturbances (22–37%). High prevalence rates of mental health symptoms were particularly among females, the elderly, individuals with prior mental illness, and those from deprived areas. Sleep disturbances emerged as common and debilitating. These symptoms significantly impair quality of life and work capacity. The review highlights the urgent need for UK-specific health policies and support services addressing the long-term mental health effects of long COVID-19.