In the APPswe/PS1δE9 (APP/PS1) model Liu et al. [12] reports 5-HT neurodegeneration to precede the onset of anxiety-related behaviours, such as thigmotaxis, becoming evident from 18 months of age, and also to precede reduced motor activity in the open field (OF) test, apparent from 24 months of age. Here, APP is linked to Anxiety.