A small number of COVID-19 patients worldwide are experiencing severe psychotic symptoms, The New York Times reported on Monday. While COVID-19 has been linked to psychological effects, most notably “brain fog,” researchers have begun to publish papers on more severe cases of psychosis, even in patients with no prior history of mental illness. One paper, published by the NIH’s National Library of Medicine, describes a 52-year-old man who developed suicidal paranoia after contracting the virus. As with much of the lesser-known symptoms of the coronavirus, medical researches do not yet know much about what causes these effects.