Comparing the current behavioural findings with those of previous studies of EV administration, peripheral injection of IFN-β-activated serum EVs in naïve recipient rats elicited mild sickness behaviour in the form of decreased locomotion as measured soon after administration [30], and the peripheral infusion of serum EVs isolated from MDD patients in naïve recipient mice induced decreased activity in the forced swim and tail suspension tests, and increased novelty suppressed feeding as measured soon after administration [22]. Here, IFNB1 is linked to major depressive disorder.