The size of the ACME of GM volume in the association between SV2A PET and plasma GFAP was comparable to that of the total study population in both the amyloid-negative subset [ACME = −0.11 (−0.24 to −0.003), 19% mediation, P = 0.080, Supplementary Fig. 5A] and the subset without late-life depression diagnosis [ACME = −0.14 (−0.38 to 0.01), 25% mediation, P = 0.17, Supplementary Fig. 5B], but did not reach significance. Here, GFAP is linked to depressive disorder.