Hi, guys. I'd like suggest something.
Some zombie media (comics, movies, books, etc) explore the psychological effect on zombie apocalypse survivors.
Maybe, Project Zomboid should explore that too. AFAIK, depression moodle just increase the time to complete some tasks. PZ could have a bar (like the health bar) measuring the character's mental stability. Each day that bar decays a little. If character is sad, bored, stressed or depressed, it decays faster.
If that stat is too low, the character may have outbursts, destroying items, food, spending ammo or just shouting, for instance. While outbursting, the player loose control over the character for a short time. It can be fatal if the outburst occur while surrounded by zombies, and it is another factor to consider regarding character's panic.
If mental stability drops to zero, the character goes insane and, for all purposes, he is as good (and dead) as a zombie.
To make matters a little more complicated, increase mental stability gets harder as lower it gets and can only be increased a pinch each day (representing the longer time needed to fix mental issues, compared with physical wounds).
So far, panic, stress and depression are just an inconvenient. With an improvement like that, those moodles will get a high importance.
I could mod that, but I don't know if that improvement can be made thru modding. I know a little Lua myself, but I think that will require messing with game's java files. Some dev can drop me a hint about that?