In the COVID group (n = 53 of 161, R2 = 0.68, P < 0.001), cognitive deficits were associated with symptoms of depression (−0.056 (0.028), P = 0.050), increased multimorbidity (−0.20 (0.083), P = 0.021) and a raised GFAP (−0.0081 (0.0032), P = 0.017). Here, GFAP is linked to major depressive disorder.