These include abnormal anxiety-like behaviours,30 hyperactivity,29 cognitive impairment19 but also a resilience to depressive-like behaviours induced by chronic stress or inflammation.31-33 Although the observed involvement of C3aR1 in adult behaviour suggests that it is needed for normal brain function, previous studies have not addressed the question of whether these phenotypes arise because of a C3aR1 deficit during development or because it is continuously needed, which can be resolved through longitudinal assessment. This evidence concerns the gene C3AR1 and Anxiety.