ELI5 Anxiety - when does worry become a disorder?

What is anxiety, and how does it become a disorder? What is happening physiologically when people describe getting an anxiety lump? How is anxiety different from depression? How is clinical depression diagnosed? Why do mental health symptoms seem more intrusive, disruptive and severe at night time? Why does exercise appear to help with mental health? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: aroundtheworldwithme, togoboldly, reallybigleg, mol-view, whatifim80lol, crazycatlushie, throwawaytherulebook, franklydankmemes, jetfuelfire To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]