Prevalence of mental health conditions and brain fog in people with long COVID: A systematic review and meta-analysis

Objective: Long COVID can include impaired cognition ('brain fog'; a term encompassing multiple symptoms) and mental health conditions. We performed a systematic review and meta-analysis to estimate their prevalence and to explore relevant factors associated with the incidence of impaired cognition and mental health conditions. Methods: Searches were conducted in Medline and PsycINFO to cover the start of the pandemic until August 2023. Included studies reported prevalence of mental health conditions and brain fog in adults with long COVID after clinically-diagnosed or PCR-confirmed SARS-CoV-2 infection. Findings: 17 studies were included, reporting 41,249 long COVID patients. Across all timepoints (3-24 months), the combined prevalence of mental health conditions and brain fog was 20.4% (95% CI 11.1%-34.4%), being lower among those previously hospitalised than in community-managed patients(19.5 vs 29.7% respectively; p = 0.047). The odds of mental health conditions and brain fog increased over time and when validated instruments were used. Odds of brain fog significantly decreased with increasing vaccination rates (p = .000). Conclusions: Given the increasing prevalence of mental health conditions and brain fog over time, preventive interventions and treatments are needed. Research is needed to explore underlying mechanisms that could inform further research in development of effective treatments. The reduced risk of brain fog associated with vaccination emphasizes the need for ongoing vaccination programs.